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Signalling and Bioactive Metabolites from Streptomyces sp. RK44

Identifieur interne : 000726 ( Pmc/Corpus ); précédent : 000725; suivant : 000727

Signalling and Bioactive Metabolites from Streptomyces sp. RK44

Auteurs : Qing Fang ; Fleurdeliz Maglangit ; Linrui Wu ; Rainer Ebel ; Kwaku Kyeremeh ; Jeanette H. Andersen ; Frederick Annang ; Guiomar Pérez-Moreno ; Fernando Reyes ; Hai Deng

Source :

RBID : PMC:7037778

Abstract

Streptomyces remains one of the prolific sources of structural diversity, and a reservoir to mine for novel natural products. Continued screening for new Streptomyces strains in our laboratory led to the isolation of Streptomyces sp. RK44 from the underexplored areas of Kintampo waterfalls, Ghana, Africa. Preliminary screening of the metabolites from this strain resulted in the characterization of a new 2-alkyl-4-hydroxymethylfuran carboxamide (AHFA) 1 together with five known compounds, cyclo-(L-Pro-Gly) 2, cyclo-(L-Pro-L-Phe) 3, cyclo-(L-Pro-L-Val) 4, cyclo-(L-Leu-Hyp) 5, and deferoxamine E 6. AHFA 1, a methylenomycin (MMF) homolog, exhibited anti-proliferative activity (EC50 = 89.6 µM) against melanoma A2058 cell lines. This activity, albeit weak is the first report amongst MMFs. Furthermore, the putative biosynthetic gene cluster (ahfa) was identified for the biosynthesis of AHFA 1. DFO-E 6 displayed potent anti-plasmodial activity (IC50 = 1.08 µM) against P. falciparum 3D7. High-resolution electrospray ionization mass spectrometry (HR ESIMS) and molecular network assisted the targeted-isolation process, and tentatively identified six AHFA analogues, 7–12 and six siderophores 13–18.


Url:
DOI: 10.3390/molecules25030460
PubMed: 31979050
PubMed Central: 7037778

Links to Exploration step

PMC:7037778

Le document en format XML

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<name sortKey="Annang, Frederick" sort="Annang, Frederick" uniqKey="Annang F" first="Frederick" last="Annang">Frederick Annang</name>
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<nlm:aff id="af5-molecules-25-00460">Fundación MEDINA, Avda. del Conocimiento 34, 18016 Armilla, Granada, Spain;
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<email>fernando.reyes@medinaandalucia.es</email>
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<email>guiomar@ipb.csic.es</email>
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<email>freddie.annang@medinaandalucia.es</email>
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<email>fernando.reyes@medinaandalucia.es</email>
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<name sortKey="Deng, Hai" sort="Deng, Hai" uniqKey="Deng H" first="Hai" last="Deng">Hai Deng</name>
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(Q.F.);
<email>r01fm16@abdn.ac.uk</email>
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<title xml:lang="en" level="a" type="main">Signalling and Bioactive Metabolites from
<italic>Streptomyces</italic>
sp. RK44</title>
<author>
<name sortKey="Fang, Qing" sort="Fang, Qing" uniqKey="Fang Q" first="Qing" last="Fang">Qing Fang</name>
<affiliation>
<nlm:aff id="af1-molecules-25-00460">Marine Biodiscovery Centre, Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, UK;
<email>r01qf16@abdn.ac.uk</email>
(Q.F.);
<email>r01fm16@abdn.ac.uk</email>
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<email>r03lw15@abdn.ac.uk</email>
(L.W.);
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</affiliation>
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<author>
<name sortKey="Maglangit, Fleurdeliz" sort="Maglangit, Fleurdeliz" uniqKey="Maglangit F" first="Fleurdeliz" last="Maglangit">Fleurdeliz Maglangit</name>
<affiliation>
<nlm:aff id="af1-molecules-25-00460">Marine Biodiscovery Centre, Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, UK;
<email>r01qf16@abdn.ac.uk</email>
(Q.F.);
<email>r01fm16@abdn.ac.uk</email>
(F.M.);
<email>r03lw15@abdn.ac.uk</email>
(L.W.);
<email>r.ebel@abdn.ac.uk</email>
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</affiliation>
<affiliation>
<nlm:aff id="af2-molecules-25-00460">College of Science, Department of Biology and Environmental Science, University of the Philippines Cebu, Lahug, Cebu 6000, Philippines</nlm:aff>
</affiliation>
</author>
<author>
<name sortKey="Wu, Linrui" sort="Wu, Linrui" uniqKey="Wu L" first="Linrui" last="Wu">Linrui Wu</name>
<affiliation>
<nlm:aff id="af1-molecules-25-00460">Marine Biodiscovery Centre, Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, UK;
<email>r01qf16@abdn.ac.uk</email>
(Q.F.);
<email>r01fm16@abdn.ac.uk</email>
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<email>r03lw15@abdn.ac.uk</email>
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<email>r.ebel@abdn.ac.uk</email>
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<name sortKey="Ebel, Rainer" sort="Ebel, Rainer" uniqKey="Ebel R" first="Rainer" last="Ebel">Rainer Ebel</name>
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<nlm:aff id="af1-molecules-25-00460">Marine Biodiscovery Centre, Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, UK;
<email>r01qf16@abdn.ac.uk</email>
(Q.F.);
<email>r01fm16@abdn.ac.uk</email>
(F.M.);
<email>r03lw15@abdn.ac.uk</email>
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<email>r.ebel@abdn.ac.uk</email>
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<name sortKey="Kyeremeh, Kwaku" sort="Kyeremeh, Kwaku" uniqKey="Kyeremeh K" first="Kwaku" last="Kyeremeh">Kwaku Kyeremeh</name>
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<nlm:aff id="af3-molecules-25-00460">Marine and Plant Research Laboratory of Ghana, Department of Chemistry, University of Ghana, P.O. Box LG56 Legon, Accra, Ghana;
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</affiliation>
</author>
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<name sortKey="Andersen, Jeanette H" sort="Andersen, Jeanette H" uniqKey="Andersen J" first="Jeanette H." last="Andersen">Jeanette H. Andersen</name>
<affiliation>
<nlm:aff id="af4-molecules-25-00460">Marbio, UiT—The Arctic University of Norway, N-9037 Tromsø, Norway;
<email>jeanette.h.andersen@uit.no</email>
</nlm:aff>
</affiliation>
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<author>
<name sortKey="Annang, Frederick" sort="Annang, Frederick" uniqKey="Annang F" first="Frederick" last="Annang">Frederick Annang</name>
<affiliation>
<nlm:aff id="af5-molecules-25-00460">Fundación MEDINA, Avda. del Conocimiento 34, 18016 Armilla, Granada, Spain;
<email>freddie.annang@medinaandalucia.es</email>
(F.A.);
<email>fernando.reyes@medinaandalucia.es</email>
(F.R.)</nlm:aff>
</affiliation>
</author>
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<name sortKey="Perez Moreno, Guiomar" sort="Perez Moreno, Guiomar" uniqKey="Perez Moreno G" first="Guiomar" last="Pérez-Moreno">Guiomar Pérez-Moreno</name>
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<nlm:aff id="af6-molecules-25-00460">Instituto de Parasitología y Biomedicina “López-Neyra”, Consejo Superior de Investigaciones Científicas (CSIC) Avda. del Conocimiento 17, 18016 Armilla, Granada, Spain;
<email>guiomar@ipb.csic.es</email>
</nlm:aff>
</affiliation>
</author>
<author>
<name sortKey="Reyes, Fernando" sort="Reyes, Fernando" uniqKey="Reyes F" first="Fernando" last="Reyes">Fernando Reyes</name>
<affiliation>
<nlm:aff id="af5-molecules-25-00460">Fundación MEDINA, Avda. del Conocimiento 34, 18016 Armilla, Granada, Spain;
<email>freddie.annang@medinaandalucia.es</email>
(F.A.);
<email>fernando.reyes@medinaandalucia.es</email>
(F.R.)</nlm:aff>
</affiliation>
</author>
<author>
<name sortKey="Deng, Hai" sort="Deng, Hai" uniqKey="Deng H" first="Hai" last="Deng">Hai Deng</name>
<affiliation>
<nlm:aff id="af1-molecules-25-00460">Marine Biodiscovery Centre, Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, UK;
<email>r01qf16@abdn.ac.uk</email>
(Q.F.);
<email>r01fm16@abdn.ac.uk</email>
(F.M.);
<email>r03lw15@abdn.ac.uk</email>
(L.W.);
<email>r.ebel@abdn.ac.uk</email>
(R.E.)</nlm:aff>
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<series>
<title level="j">Molecules</title>
<idno type="eISSN">1420-3049</idno>
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<front>
<div type="abstract" xml:lang="en">
<p>
<italic>Streptomyces</italic>
remains one of the prolific sources of structural diversity, and a reservoir to mine for novel natural products. Continued screening for new Streptomyces strains in our laboratory led to the isolation of
<italic>Streptomyces</italic>
sp. RK44 from the underexplored areas of Kintampo waterfalls, Ghana, Africa. Preliminary screening of the metabolites from this strain resulted in the characterization of a new 2-alkyl-4-hydroxymethylfuran carboxamide (AHFA)
<bold>1</bold>
together with five known compounds, cyclo-(L-Pro-Gly)
<bold>2</bold>
, cyclo-(L-Pro-L-Phe)
<bold>3</bold>
, cyclo-(L-Pro-L-Val)
<bold>4</bold>
, cyclo-(L-Leu-Hyp)
<bold>5</bold>
, and deferoxamine E
<bold>6</bold>
. AHFA
<bold>1</bold>
, a methylenomycin (MMF) homolog, exhibited anti-proliferative activity (EC
<sub>50</sub>
= 89.6 µM) against melanoma A2058 cell lines. This activity, albeit weak is the first report amongst MMFs. Furthermore, the putative biosynthetic gene cluster (
<italic>ahfa</italic>
) was identified for the biosynthesis of AHFA
<bold>1</bold>
. DFO-E
<bold>6</bold>
displayed potent anti-plasmodial activity (IC
<sub>50</sub>
= 1.08 µM) against
<italic>P. falciparum</italic>
3D7. High-resolution electrospray ionization mass spectrometry (HR ESIMS) and molecular network assisted the targeted-isolation process, and tentatively identified six AHFA analogues,
<bold>7</bold>
–
<bold>12</bold>
and six siderophores
<bold>13</bold>
–
<bold>18</bold>
.</p>
</div>
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<div1 type="bibliography">
<listBibl>
<biblStruct>
<analytic>
<author>
<name sortKey="Eliakim Raz, N" uniqKey="Eliakim Raz N">N. Eliakim-Raz</name>
</author>
<author>
<name sortKey="Lador, A" uniqKey="Lador A">A. Lador</name>
</author>
<author>
<name sortKey="Leibovici Weissman, Y" uniqKey="Leibovici Weissman Y">Y. Leibovici-Weissman</name>
</author>
<author>
<name sortKey="Elbaz, M" uniqKey="Elbaz M">M. Elbaz</name>
</author>
<author>
<name sortKey="Paul, M" uniqKey="Paul M">M. Paul</name>
</author>
<author>
<name sortKey="Leibovici, L" uniqKey="Leibovici L">L. Leibovici</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Falagas, M E" uniqKey="Falagas M">M.E. Falagas</name>
</author>
<author>
<name sortKey="Vouloumanou, E K" uniqKey="Vouloumanou E">E.K. Vouloumanou</name>
</author>
<author>
<name sortKey="Samonis, G" uniqKey="Samonis G">G. Samonis</name>
</author>
<author>
<name sortKey="Vardakas, K Z" uniqKey="Vardakas K">K.Z. Vardakas</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Vons, C" uniqKey="Vons C">C. Vons</name>
</author>
<author>
<name sortKey="Barry, C" uniqKey="Barry C">C. Barry</name>
</author>
<author>
<name sortKey="Maitre, S" uniqKey="Maitre S">S. Maitre</name>
</author>
<author>
<name sortKey="Pautrat, K" uniqKey="Pautrat K">K. Pautrat</name>
</author>
<author>
<name sortKey="Leconte, M" uniqKey="Leconte M">M. Leconte</name>
</author>
<author>
<name sortKey="Costaglioli, B" uniqKey="Costaglioli B">B. Costaglioli</name>
</author>
<author>
<name sortKey="Karoui, M" uniqKey="Karoui M">M. Karoui</name>
</author>
<author>
<name sortKey="Alves, A" uniqKey="Alves A">A. Alves</name>
</author>
<author>
<name sortKey="Dousset, B" uniqKey="Dousset B">B. Dousset</name>
</author>
<author>
<name sortKey="Valleur, P" uniqKey="Valleur P">P. Valleur</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Kitani, S" uniqKey="Kitani S">S. Kitani</name>
</author>
<author>
<name sortKey="Miyamoto, K T" uniqKey="Miyamoto K">K.T. Miyamoto</name>
</author>
<author>
<name sortKey="Takamatsu, S" uniqKey="Takamatsu S">S. Takamatsu</name>
</author>
<author>
<name sortKey="Herawati, E" uniqKey="Herawati E">E. Herawati</name>
</author>
<author>
<name sortKey="Iguchi, H" uniqKey="Iguchi H">H. Iguchi</name>
</author>
<author>
<name sortKey="Nishitomi, K" uniqKey="Nishitomi K">K. Nishitomi</name>
</author>
<author>
<name sortKey="Uchida, M" uniqKey="Uchida M">M. Uchida</name>
</author>
<author>
<name sortKey="Nagamitsu, T" uniqKey="Nagamitsu T">T. Nagamitsu</name>
</author>
<author>
<name sortKey="Omura, S" uniqKey="Omura S">S. Omura</name>
</author>
<author>
<name sortKey="Ikeda, H" uniqKey="Ikeda H">H. Ikeda</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Maglangit, F" uniqKey="Maglangit F">F. Maglangit</name>
</author>
<author>
<name sortKey="Fang, Q" uniqKey="Fang Q">Q. Fang</name>
</author>
<author>
<name sortKey="Leman, V" uniqKey="Leman V">V. Leman</name>
</author>
<author>
<name sortKey="Soldatou, S" uniqKey="Soldatou S">S. Soldatou</name>
</author>
<author>
<name sortKey="Ebel, R" uniqKey="Ebel R">R. Ebel</name>
</author>
<author>
<name sortKey="Deng, H" uniqKey="Deng H">H. Deng</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Maglangit, F" uniqKey="Maglangit F">F. Maglangit</name>
</author>
<author>
<name sortKey="Fang, Q" uniqKey="Fang Q">Q. Fang</name>
</author>
<author>
<name sortKey="Kyeremeh, K" uniqKey="Kyeremeh K">K. Kyeremeh</name>
</author>
<author>
<name sortKey="Sternberg, J M" uniqKey="Sternberg J">J.M. Sternberg</name>
</author>
<author>
<name sortKey="Ebel, R" uniqKey="Ebel R">R. Ebel</name>
</author>
<author>
<name sortKey="Deng, H" uniqKey="Deng H">H. Deng</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Wang, M" uniqKey="Wang M">M. Wang</name>
</author>
<author>
<name sortKey="Carver, J J" uniqKey="Carver J">J.J. Carver</name>
</author>
<author>
<name sortKey="Phelan, V V" uniqKey="Phelan V">V.V. Phelan</name>
</author>
<author>
<name sortKey="Sanchez, L M" uniqKey="Sanchez L">L.M. Sanchez</name>
</author>
<author>
<name sortKey="Garg, N" uniqKey="Garg N">N. Garg</name>
</author>
<author>
<name sortKey="Peng, Y" uniqKey="Peng Y">Y. Peng</name>
</author>
<author>
<name sortKey="Nguyen, D D" uniqKey="Nguyen D">D.D. Nguyen</name>
</author>
<author>
<name sortKey="Watrous, J" uniqKey="Watrous J">J. Watrous</name>
</author>
<author>
<name sortKey="Kapono, C A" uniqKey="Kapono C">C.A. Kapono</name>
</author>
<author>
<name sortKey="Luzzatto Knaan, T" uniqKey="Luzzatto Knaan T">T. Luzzatto-Knaan</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Santen, J" uniqKey="Santen J">J. Santen</name>
</author>
<author>
<name sortKey="Van, A" uniqKey="Van A">A. Van</name>
</author>
<author>
<name sortKey="Jacob, G" uniqKey="Jacob G">G. Jacob</name>
</author>
<author>
<name sortKey="Singh, A L" uniqKey="Singh A">A.L. Singh</name>
</author>
<author>
<name sortKey="Aniebok, V" uniqKey="Aniebok V">V. Aniebok</name>
</author>
<author>
<name sortKey="Balunas, M J" uniqKey="Balunas M">M.J. Balunas</name>
</author>
<author>
<name sortKey="Bunsko, D" uniqKey="Bunsko D">D. Bunsko</name>
</author>
<author>
<name sortKey="Neto, F C" uniqKey="Neto F">F.C. Neto</name>
</author>
<author>
<name sortKey="Casta O Espriu, L" uniqKey="Casta O Espriu L">L. Castaño-Espriu</name>
</author>
<author>
<name sortKey="Chang, C" uniqKey="Chang C">C. Chang</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Pence, H E" uniqKey="Pence H">H.E. Pence</name>
</author>
<author>
<name sortKey="Williams, A" uniqKey="Williams A">A. Williams</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Ito, T" uniqKey="Ito T">T. Ito</name>
</author>
<author>
<name sortKey="Masubuchi, M" uniqKey="Masubuchi M">M. Masubuchi</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Crusemann, M" uniqKey="Crusemann M">M. Crüsemann</name>
</author>
<author>
<name sortKey="O Eill, E C" uniqKey="O Eill E">E.C. O’Neill</name>
</author>
<author>
<name sortKey="Larson, C B" uniqKey="Larson C">C.B. Larson</name>
</author>
<author>
<name sortKey="Melnik, A V" uniqKey="Melnik A">A.V. Melnik</name>
</author>
<author>
<name sortKey="Floros, D J" uniqKey="Floros D">D.J. Floros</name>
</author>
<author>
<name sortKey="Da Silva, R R" uniqKey="Da Silva R">R.R. Da Silva</name>
</author>
<author>
<name sortKey="Jensen, P R" uniqKey="Jensen P">P.R. Jensen</name>
</author>
<author>
<name sortKey="Dorrestein, P C" uniqKey="Dorrestein P">P.C. Dorrestein</name>
</author>
<author>
<name sortKey="Moore, B S" uniqKey="Moore B">B.S. Moore</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Corre, C" uniqKey="Corre C">C. Corre</name>
</author>
<author>
<name sortKey="Song, L" uniqKey="Song L">L. Song</name>
</author>
<author>
<name sortKey="O Ourke, S" uniqKey="O Ourke S">S. O’Rourke</name>
</author>
<author>
<name sortKey="Chater, K F" uniqKey="Chater K">K.F. Chater</name>
</author>
<author>
<name sortKey="Challis, G L" uniqKey="Challis G">G.L. Challis</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Schuster, M" uniqKey="Schuster M">M. Schuster</name>
</author>
<author>
<name sortKey="Joseph Sexton, D" uniqKey="Joseph Sexton D">D. Joseph Sexton</name>
</author>
<author>
<name sortKey="Diggle, S P" uniqKey="Diggle S">S.P. Diggle</name>
</author>
<author>
<name sortKey="Peter Greenberg, E" uniqKey="Peter Greenberg E">E. Peter Greenberg</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Sidda, J D" uniqKey="Sidda J">J.D. Sidda</name>
</author>
<author>
<name sortKey="Poon, V" uniqKey="Poon V">V. Poon</name>
</author>
<author>
<name sortKey="Song, L" uniqKey="Song L">L. Song</name>
</author>
<author>
<name sortKey="Wang, W" uniqKey="Wang W">W. Wang</name>
</author>
<author>
<name sortKey="Yang, K" uniqKey="Yang K">K. Yang</name>
</author>
<author>
<name sortKey="Corre, C" uniqKey="Corre C">C. Corre</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Du, Y L" uniqKey="Du Y">Y.L. Du</name>
</author>
<author>
<name sortKey="Shen, X L" uniqKey="Shen X">X.L. Shen</name>
</author>
<author>
<name sortKey="Yu, P" uniqKey="Yu P">P. Yu</name>
</author>
<author>
<name sortKey="Bai, L Q" uniqKey="Bai L">L.Q. Bai</name>
</author>
<author>
<name sortKey="Li, Y Q" uniqKey="Li Y">Y.Q. Li</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Bhasin, S" uniqKey="Bhasin S">S. Bhasin</name>
</author>
<author>
<name sortKey="Modi, H A" uniqKey="Modi H">H.A. Modi</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Li, X" uniqKey="Li X">X. Li</name>
</author>
<author>
<name sortKey="Dobretsov, S" uniqKey="Dobretsov S">S. Dobretsov</name>
</author>
<author>
<name sortKey="Xu, Y" uniqKey="Xu Y">Y. Xu</name>
</author>
<author>
<name sortKey="Xiao, X" uniqKey="Xiao X">X. Xiao</name>
</author>
<author>
<name sortKey="Hung, O" uniqKey="Hung O">O. Hung</name>
</author>
<author>
<name sortKey="Qian, P Y" uniqKey="Qian P">P.Y. Qian</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Campo, V L" uniqKey="Campo V">V.L. Campo</name>
</author>
<author>
<name sortKey="Duarte, M C T" uniqKey="Duarte M">M.C.T. Duarte</name>
</author>
<author>
<name sortKey="Bastos, J K" uniqKey="Bastos J">J.K. Bastos</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Lee, S R" uniqKey="Lee S">S.R. Lee</name>
</author>
<author>
<name sortKey="Beemelmanns, C" uniqKey="Beemelmanns C">C. Beemelmanns</name>
</author>
<author>
<name sortKey="Tsuma, L M M" uniqKey="Tsuma L">L.M.M. Tsuma</name>
</author>
<author>
<name sortKey="Clardy, J" uniqKey="Clardy J">J. Clardy</name>
</author>
<author>
<name sortKey="Cao, S" uniqKey="Cao S">S. Cao</name>
</author>
<author>
<name sortKey="Kim, K H" uniqKey="Kim K">K.H. Kim</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Alshaibani, M" uniqKey="Alshaibani M">M. Alshaibani</name>
</author>
<author>
<name sortKey="Jalil, J" uniqKey="Jalil J">J. Jalil</name>
</author>
<author>
<name sortKey="Sidik, N" uniqKey="Sidik N">N. Sidik</name>
</author>
<author>
<name sortKey="Ahmad, S" uniqKey="Ahmad S">S. Ahmad</name>
</author>
<author>
<name sortKey="Kamal, N" uniqKey="Kamal N">N. Kamal</name>
</author>
<author>
<name sortKey="Edrada Ebel, R" uniqKey="Edrada Ebel R">R. Edrada-Ebel</name>
</author>
<author>
<name sortKey="Mohamadzin, N" uniqKey="Mohamadzin N">N. MohamadZin</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Nishanth Kumar, S" uniqKey="Nishanth Kumar S">S. Nishanth Kumar</name>
</author>
<author>
<name sortKey="Mohandas, C" uniqKey="Mohandas C">C. Mohandas</name>
</author>
<author>
<name sortKey="Siji, J V" uniqKey="Siji J">J.V. Siji</name>
</author>
<author>
<name sortKey="Rajasekharan, K N" uniqKey="Rajasekharan K">K.N. Rajasekharan</name>
</author>
<author>
<name sortKey="Nambisan, B" uniqKey="Nambisan B">B. Nambisan</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Maglangit, F" uniqKey="Maglangit F">F. Maglangit</name>
</author>
<author>
<name sortKey="Tong, M H" uniqKey="Tong M">M.H. Tong</name>
</author>
<author>
<name sortKey="Jaspars, M" uniqKey="Jaspars M">M. Jaspars</name>
</author>
<author>
<name sortKey="Kyeremeh, K" uniqKey="Kyeremeh K">K. Kyeremeh</name>
</author>
<author>
<name sortKey="Deng, H" uniqKey="Deng H">H. Deng</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Yamanaka, K" uniqKey="Yamanaka K">K. Yamanaka</name>
</author>
<author>
<name sortKey="Oikawa, H" uniqKey="Oikawa H">H. Oikawa</name>
</author>
<author>
<name sortKey="Ogawa, H O" uniqKey="Ogawa H">H.O. Ogawa</name>
</author>
<author>
<name sortKey="Hosono, K" uniqKey="Hosono K">K. Hosono</name>
</author>
<author>
<name sortKey="Shinmachi, F" uniqKey="Shinmachi F">F. Shinmachi</name>
</author>
<author>
<name sortKey="Takano, H" uniqKey="Takano H">H. Takano</name>
</author>
<author>
<name sortKey="Sakuda, S" uniqKey="Sakuda S">S. Sakuda</name>
</author>
<author>
<name sortKey="Beppu, T" uniqKey="Beppu T">T. Beppu</name>
</author>
<author>
<name sortKey="Ueda, K" uniqKey="Ueda K">K. Ueda</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Meiwes, J" uniqKey="Meiwes J">J. Meiwes</name>
</author>
<author>
<name sortKey="Fiedler, H P" uniqKey="Fiedler H">H.P. Fiedler</name>
</author>
<author>
<name sortKey="Z Hner, H" uniqKey="Z Hner H">H. Zähner</name>
</author>
<author>
<name sortKey="Konetschny Rapp, S" uniqKey="Konetschny Rapp S">S. Konetschny-Rapp</name>
</author>
<author>
<name sortKey="Jung, G" uniqKey="Jung G">G. Jung</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Corre, C" uniqKey="Corre C">C. Corre</name>
</author>
<author>
<name sortKey="Haynes, S W" uniqKey="Haynes S">S.W. Haynes</name>
</author>
<author>
<name sortKey="Malet, N" uniqKey="Malet N">N. Malet</name>
</author>
<author>
<name sortKey="Song, L" uniqKey="Song L">L. Song</name>
</author>
<author>
<name sortKey="Challis, G L" uniqKey="Challis G">G.L. Challis</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Weber, T" uniqKey="Weber T">T. Weber</name>
</author>
<author>
<name sortKey="Blin, K" uniqKey="Blin K">K. Blin</name>
</author>
<author>
<name sortKey="Duddela, S" uniqKey="Duddela S">S. Duddela</name>
</author>
<author>
<name sortKey="Krug, D" uniqKey="Krug D">D. Krug</name>
</author>
<author>
<name sortKey="Kim, H U" uniqKey="Kim H">H.U. Kim</name>
</author>
<author>
<name sortKey="Bruccoleri, R" uniqKey="Bruccoleri R">R. Bruccoleri</name>
</author>
<author>
<name sortKey="Lee, S Y" uniqKey="Lee S">S.Y. Lee</name>
</author>
<author>
<name sortKey="Fischbach, M A" uniqKey="Fischbach M">M.A. Fischbach</name>
</author>
<author>
<name sortKey="Muller, R" uniqKey="Muller R">R. Müller</name>
</author>
<author>
<name sortKey="Wohlleben, W" uniqKey="Wohlleben W">W. Wohlleben</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Sayers, E W" uniqKey="Sayers E">E.W. Sayers</name>
</author>
<author>
<name sortKey="Agarwala, R" uniqKey="Agarwala R">R. Agarwala</name>
</author>
<author>
<name sortKey="Bolton, E E" uniqKey="Bolton E">E.E. Bolton</name>
</author>
<author>
<name sortKey="Brister, J R" uniqKey="Brister J">J.R. Brister</name>
</author>
<author>
<name sortKey="Canese, K" uniqKey="Canese K">K. Canese</name>
</author>
<author>
<name sortKey="Clark, K" uniqKey="Clark K">K. Clark</name>
</author>
<author>
<name sortKey="Connor, R" uniqKey="Connor R">R. Connor</name>
</author>
<author>
<name sortKey="Fiorini, N" uniqKey="Fiorini N">N. Fiorini</name>
</author>
<author>
<name sortKey="Funk, K" uniqKey="Funk K">K. Funk</name>
</author>
<author>
<name sortKey="Hefferon, T" uniqKey="Hefferon T">T. Hefferon</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Zallot, R" uniqKey="Zallot R">R. Zallot</name>
</author>
<author>
<name sortKey="Oberg, N O" uniqKey="Oberg N">N.O. Oberg</name>
</author>
<author>
<name sortKey="Gerlt, J A" uniqKey="Gerlt J">J.A. Gerlt</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Horinouchi, S" uniqKey="Horinouchi S">S. Horinouchi</name>
</author>
<author>
<name sortKey="Beppu, T" uniqKey="Beppu T">T. Beppu</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Davis, J B" uniqKey="Davis J">J.B. Davis</name>
</author>
<author>
<name sortKey="Bailey, J D" uniqKey="Bailey J">J.D. Bailey</name>
</author>
<author>
<name sortKey="Sello, J K" uniqKey="Sello J">J.K. Sello</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Alberti, F" uniqKey="Alberti F">F. Alberti</name>
</author>
<author>
<name sortKey="Leng, D J" uniqKey="Leng D">D.J. Leng</name>
</author>
<author>
<name sortKey="Wilkening, I" uniqKey="Wilkening I">I. Wilkening</name>
</author>
<author>
<name sortKey="Song, L" uniqKey="Song L">L. Song</name>
</author>
<author>
<name sortKey="Tosin, M" uniqKey="Tosin M">M. Tosin</name>
</author>
<author>
<name sortKey="Corre, C" uniqKey="Corre C">C. Corre</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Gordeuk, V R" uniqKey="Gordeuk V">V.R. Gordeuk</name>
</author>
<author>
<name sortKey="Thuma, P E" uniqKey="Thuma P">P.E. Thuma</name>
</author>
<author>
<name sortKey="Brittenbam, G M" uniqKey="Brittenbam G">G.M. Brittenbam</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Rotheneder, A" uniqKey="Rotheneder A">A. Rotheneder</name>
</author>
<author>
<name sortKey="Fritsche, G" uniqKey="Fritsche G">G. Fritsche</name>
</author>
<author>
<name sortKey="Heinisch, L" uniqKey="Heinisch L">L. Heinisch</name>
</author>
<author>
<name sortKey="Heggemann, S" uniqKey="Heggemann S">S. Heggemann</name>
</author>
<author>
<name sortKey="Larcher, C" uniqKey="Larcher C">C. Larcher</name>
</author>
<author>
<name sortKey="Mollmann, U" uniqKey="Mollmann U">U. Möllmann</name>
</author>
<author>
<name sortKey="Weiss, G" uniqKey="Weiss G">G. Weiss</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Ferrer, P" uniqKey="Ferrer P">P. Ferrer</name>
</author>
<author>
<name sortKey="Tripathi, A K" uniqKey="Tripathi A">A.K. Tripathi</name>
</author>
<author>
<name sortKey="Clark, M A" uniqKey="Clark M">M.A. Clark</name>
</author>
<author>
<name sortKey="Hand, C C" uniqKey="Hand C">C.C. Hand</name>
</author>
<author>
<name sortKey="Rienhoff, H Y" uniqKey="Rienhoff H">H.Y. Rienhoff</name>
</author>
<author>
<name sortKey="Sullivan, D J" uniqKey="Sullivan D">D.J. Sullivan</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Pradines, B" uniqKey="Pradines B">B. Pradines</name>
</author>
<author>
<name sortKey="Rolain, J M" uniqKey="Rolain J">J.M. Rolain</name>
</author>
<author>
<name sortKey="Ramiandrasoa, F" uniqKey="Ramiandrasoa F">F. Ramiandrasoa</name>
</author>
<author>
<name sortKey="Fusai, T" uniqKey="Fusai T">T. Fusai</name>
</author>
<author>
<name sortKey="Mosnier, J" uniqKey="Mosnier J">J. Mosnier</name>
</author>
<author>
<name sortKey="Rogier, C" uniqKey="Rogier C">C. Rogier</name>
</author>
<author>
<name sortKey="Daries, W" uniqKey="Daries W">W. Daries</name>
</author>
<author>
<name sortKey="Baret, E" uniqKey="Baret E">E. Baret</name>
</author>
<author>
<name sortKey="Kunesch, G" uniqKey="Kunesch G">G. Kunesch</name>
</author>
<author>
<name sortKey="Le Bras, J" uniqKey="Le Bras J">J. Le Bras</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Perez Moreno, G" uniqKey="Perez Moreno G">G. Pérez-Moreno</name>
</author>
<author>
<name sortKey="Cantizani, J" uniqKey="Cantizani J">J. Cantizani</name>
</author>
<author>
<name sortKey="Sanchez Carrasco, P" uniqKey="Sanchez Carrasco P">P. Sánchez-Carrasco</name>
</author>
<author>
<name sortKey="Ruiz Perez, L M" uniqKey="Ruiz Perez L">L.M. Ruiz-Pérez</name>
</author>
<author>
<name sortKey="Martin, J" uniqKey="Martin J">J. Martín</name>
</author>
<author>
<name sortKey="El Aouad, N" uniqKey="El Aouad N">N. El Aouad</name>
</author>
<author>
<name sortKey="Perez Victoria, I" uniqKey="Perez Victoria I">I. Pérez-Victoria</name>
</author>
<author>
<name sortKey="Tormo, J R" uniqKey="Tormo J">J.R. Tormo</name>
</author>
<author>
<name sortKey="Gonzalez Menendez, V" uniqKey="Gonzalez Menendez V">V. González-Menendez</name>
</author>
<author>
<name sortKey="Gonzalez, I" uniqKey="Gonzalez I">I. González</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Pluskal, T" uniqKey="Pluskal T">T. Pluskal</name>
</author>
<author>
<name sortKey="Castillo, S" uniqKey="Castillo S">S. Castillo</name>
</author>
<author>
<name sortKey="Villar Briones, A" uniqKey="Villar Briones A">A. Villar-Briones</name>
</author>
<author>
<name sortKey="Oresi, M" uniqKey="Oresi M">M. Orešič</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Pylayeva Gupta, Y" uniqKey="Pylayeva Gupta Y">Y. Pylayeva-Gupta</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Shannon, P" uniqKey="Shannon P">P. Shannon</name>
</author>
<author>
<name sortKey="Markiel, A" uniqKey="Markiel A">A. Markiel</name>
</author>
<author>
<name sortKey="Ozier, O" uniqKey="Ozier O">O. Ozier</name>
</author>
<author>
<name sortKey="Baliga, N S" uniqKey="Baliga N">N.S. Baliga</name>
</author>
<author>
<name sortKey="Wang, J T" uniqKey="Wang J">J.T. Wang</name>
</author>
<author>
<name sortKey="Ramage, D" uniqKey="Ramage D">D. Ramage</name>
</author>
<author>
<name sortKey="Amin, N" uniqKey="Amin N">N. Amin</name>
</author>
<author>
<name sortKey="Schwikowski, B" uniqKey="Schwikowski B">B. Schwikowski</name>
</author>
<author>
<name sortKey="Ideker, T" uniqKey="Ideker T">T. Ideker</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Aziz, R K" uniqKey="Aziz R">R.K. Aziz</name>
</author>
<author>
<name sortKey="Bartels, D" uniqKey="Bartels D">D. Bartels</name>
</author>
<author>
<name sortKey="Best, A A" uniqKey="Best A">A.A. Best</name>
</author>
<author>
<name sortKey="Dejongh, M" uniqKey="Dejongh M">M. DeJongh</name>
</author>
<author>
<name sortKey="Disz, T" uniqKey="Disz T">T. Disz</name>
</author>
<author>
<name sortKey="Edwards, R A" uniqKey="Edwards R">R.A. Edwards</name>
</author>
<author>
<name sortKey="Formsma, K" uniqKey="Formsma K">K. Formsma</name>
</author>
<author>
<name sortKey="Gerdes, S" uniqKey="Gerdes S">S. Gerdes</name>
</author>
<author>
<name sortKey="Glass, E M" uniqKey="Glass E">E.M. Glass</name>
</author>
<author>
<name sortKey="Kubal, M" uniqKey="Kubal M">M. Kubal</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Saitou, N" uniqKey="Saitou N">N. Saitou</name>
</author>
<author>
<name sortKey="Nei, M" uniqKey="Nei M">M. Nei</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Kumar, S" uniqKey="Kumar S">S. Kumar</name>
</author>
<author>
<name sortKey="Stecher, G" uniqKey="Stecher G">G. Stecher</name>
</author>
<author>
<name sortKey="Tamura, K" uniqKey="Tamura K">K. Tamura</name>
</author>
</analytic>
</biblStruct>
<biblStruct>
<analytic>
<author>
<name sortKey="Carpenter, D E" uniqKey="Carpenter D">D.E. Carpenter</name>
</author>
<author>
<name sortKey="Karen Anderson Diane Citron, C M" uniqKey="Karen Anderson Diane Citron C">C.M. Karen Anderson Diane Citron</name>
</author>
<author>
<name sortKey="Joann Dzink Fox, B L" uniqKey="Joann Dzink Fox B">B.L. JoAnn Dzink-Fox</name>
</author>
<author>
<name sortKey="Meredith Hackel, M" uniqKey="Meredith Hackel M">M. Meredith Hackel</name>
</author>
<author>
<name sortKey="Jenkins, S G" uniqKey="Jenkins S">S.G. Jenkins</name>
</author>
<author>
<name sortKey="Cindy Knapp, F" uniqKey="Cindy Knapp F">F. Cindy Knapp</name>
</author>
<author>
<name sortKey="Laura Koeth, M" uniqKey="Laura Koeth M">M. Laura Koeth</name>
</author>
<author>
<name sortKey="Audrey Schuetz, M N" uniqKey="Audrey Schuetz M">M.N. Audrey Schuetz</name>
</author>
<author>
<name sortKey="Hannah Wexler, D" uniqKey="Hannah Wexler D">D. Hannah Wexler</name>
</author>
</analytic>
</biblStruct>
</listBibl>
</div1>
</back>
</TEI>
<pmc article-type="research-article">
<pmc-dir>properties open_access</pmc-dir>
<front>
<journal-meta>
<journal-id journal-id-type="nlm-ta">Molecules</journal-id>
<journal-id journal-id-type="iso-abbrev">Molecules</journal-id>
<journal-id journal-id-type="publisher-id">molecules</journal-id>
<journal-title-group>
<journal-title>Molecules</journal-title>
</journal-title-group>
<issn pub-type="epub">1420-3049</issn>
<publisher>
<publisher-name>MDPI</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="pmid">31979050</article-id>
<article-id pub-id-type="pmc">7037778</article-id>
<article-id pub-id-type="doi">10.3390/molecules25030460</article-id>
<article-id pub-id-type="publisher-id">molecules-25-00460</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Article</subject>
</subj-group>
</article-categories>
<title-group>
<article-title>Signalling and Bioactive Metabolites from
<italic>Streptomyces</italic>
sp. RK44</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<contrib-id contrib-id-type="orcid" authenticated="true">https://orcid.org/0000-0002-8479-5482</contrib-id>
<name>
<surname>Fang</surname>
<given-names>Qing</given-names>
</name>
<xref ref-type="aff" rid="af1-molecules-25-00460">1</xref>
</contrib>
<contrib contrib-type="author">
<contrib-id contrib-id-type="orcid" authenticated="true">https://orcid.org/0000-0002-0159-8337</contrib-id>
<name>
<surname>Maglangit</surname>
<given-names>Fleurdeliz</given-names>
</name>
<xref ref-type="aff" rid="af1-molecules-25-00460">1</xref>
<xref ref-type="aff" rid="af2-molecules-25-00460">2</xref>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Wu</surname>
<given-names>Linrui</given-names>
</name>
<xref ref-type="aff" rid="af1-molecules-25-00460">1</xref>
</contrib>
<contrib contrib-type="author">
<contrib-id contrib-id-type="orcid" authenticated="true">https://orcid.org/0000-0002-9702-2235</contrib-id>
<name>
<surname>Ebel</surname>
<given-names>Rainer</given-names>
</name>
<xref ref-type="aff" rid="af1-molecules-25-00460">1</xref>
</contrib>
<contrib contrib-type="author">
<contrib-id contrib-id-type="orcid" authenticated="true">https://orcid.org/0000-0002-3644-9497</contrib-id>
<name>
<surname>Kyeremeh</surname>
<given-names>Kwaku</given-names>
</name>
<xref ref-type="aff" rid="af3-molecules-25-00460">3</xref>
</contrib>
<contrib contrib-type="author">
<contrib-id contrib-id-type="orcid" authenticated="true">https://orcid.org/0000-0002-6059-060X</contrib-id>
<name>
<surname>Andersen</surname>
<given-names>Jeanette H.</given-names>
</name>
<xref ref-type="aff" rid="af4-molecules-25-00460">4</xref>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Annang</surname>
<given-names>Frederick</given-names>
</name>
<xref ref-type="aff" rid="af5-molecules-25-00460">5</xref>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Pérez-Moreno</surname>
<given-names>Guiomar</given-names>
</name>
<xref ref-type="aff" rid="af6-molecules-25-00460">6</xref>
</contrib>
<contrib contrib-type="author">
<contrib-id contrib-id-type="orcid" authenticated="true">https://orcid.org/0000-0003-1607-5106</contrib-id>
<name>
<surname>Reyes</surname>
<given-names>Fernando</given-names>
</name>
<xref ref-type="aff" rid="af5-molecules-25-00460">5</xref>
</contrib>
<contrib contrib-type="author">
<contrib-id contrib-id-type="orcid" authenticated="true">https://orcid.org/0000-0002-0047-0622</contrib-id>
<name>
<surname>Deng</surname>
<given-names>Hai</given-names>
</name>
<xref ref-type="aff" rid="af1-molecules-25-00460">1</xref>
<xref rid="c1-molecules-25-00460" ref-type="corresp">*</xref>
</contrib>
</contrib-group>
<aff id="af1-molecules-25-00460">
<label>1</label>
Marine Biodiscovery Centre, Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, UK;
<email>r01qf16@abdn.ac.uk</email>
(Q.F.);
<email>r01fm16@abdn.ac.uk</email>
(F.M.);
<email>r03lw15@abdn.ac.uk</email>
(L.W.);
<email>r.ebel@abdn.ac.uk</email>
(R.E.)</aff>
<aff id="af2-molecules-25-00460">
<label>2</label>
College of Science, Department of Biology and Environmental Science, University of the Philippines Cebu, Lahug, Cebu 6000, Philippines</aff>
<aff id="af3-molecules-25-00460">
<label>3</label>
Marine and Plant Research Laboratory of Ghana, Department of Chemistry, University of Ghana, P.O. Box LG56 Legon, Accra, Ghana;
<email>kkyeremeh@ug.edu.gh</email>
</aff>
<aff id="af4-molecules-25-00460">
<label>4</label>
Marbio, UiT—The Arctic University of Norway, N-9037 Tromsø, Norway;
<email>jeanette.h.andersen@uit.no</email>
</aff>
<aff id="af5-molecules-25-00460">
<label>5</label>
Fundación MEDINA, Avda. del Conocimiento 34, 18016 Armilla, Granada, Spain;
<email>freddie.annang@medinaandalucia.es</email>
(F.A.);
<email>fernando.reyes@medinaandalucia.es</email>
(F.R.)</aff>
<aff id="af6-molecules-25-00460">
<label>6</label>
Instituto de Parasitología y Biomedicina “López-Neyra”, Consejo Superior de Investigaciones Científicas (CSIC) Avda. del Conocimiento 17, 18016 Armilla, Granada, Spain;
<email>guiomar@ipb.csic.es</email>
</aff>
<author-notes>
<corresp id="c1-molecules-25-00460">
<label>*</label>
Correspondence:
<email>h.deng@abdn.ac.uk</email>
; Tel.: +44-1224-272953; Fax: +44-1224-272291</corresp>
</author-notes>
<pub-date pub-type="epub">
<day>22</day>
<month>1</month>
<year>2020</year>
</pub-date>
<pub-date pub-type="collection">
<month>2</month>
<year>2020</year>
</pub-date>
<volume>25</volume>
<issue>3</issue>
<elocation-id>460</elocation-id>
<history>
<date date-type="received">
<day>22</day>
<month>12</month>
<year>2019</year>
</date>
<date date-type="accepted">
<day>21</day>
<month>1</month>
<year>2020</year>
</date>
</history>
<permissions>
<copyright-statement>© 2020 by the authors.</copyright-statement>
<copyright-year>2020</copyright-year>
<license license-type="open-access">
<license-p>Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (
<ext-link ext-link-type="uri" xlink:href="http://creativecommons.org/licenses/by/4.0/">http://creativecommons.org/licenses/by/4.0/</ext-link>
).</license-p>
</license>
</permissions>
<abstract>
<p>
<italic>Streptomyces</italic>
remains one of the prolific sources of structural diversity, and a reservoir to mine for novel natural products. Continued screening for new Streptomyces strains in our laboratory led to the isolation of
<italic>Streptomyces</italic>
sp. RK44 from the underexplored areas of Kintampo waterfalls, Ghana, Africa. Preliminary screening of the metabolites from this strain resulted in the characterization of a new 2-alkyl-4-hydroxymethylfuran carboxamide (AHFA)
<bold>1</bold>
together with five known compounds, cyclo-(L-Pro-Gly)
<bold>2</bold>
, cyclo-(L-Pro-L-Phe)
<bold>3</bold>
, cyclo-(L-Pro-L-Val)
<bold>4</bold>
, cyclo-(L-Leu-Hyp)
<bold>5</bold>
, and deferoxamine E
<bold>6</bold>
. AHFA
<bold>1</bold>
, a methylenomycin (MMF) homolog, exhibited anti-proliferative activity (EC
<sub>50</sub>
= 89.6 µM) against melanoma A2058 cell lines. This activity, albeit weak is the first report amongst MMFs. Furthermore, the putative biosynthetic gene cluster (
<italic>ahfa</italic>
) was identified for the biosynthesis of AHFA
<bold>1</bold>
. DFO-E
<bold>6</bold>
displayed potent anti-plasmodial activity (IC
<sub>50</sub>
= 1.08 µM) against
<italic>P. falciparum</italic>
3D7. High-resolution electrospray ionization mass spectrometry (HR ESIMS) and molecular network assisted the targeted-isolation process, and tentatively identified six AHFA analogues,
<bold>7</bold>
–
<bold>12</bold>
and six siderophores
<bold>13</bold>
–
<bold>18</bold>
.</p>
</abstract>
<kwd-group>
<kwd>AHFA</kwd>
<kwd>methylenomycin</kwd>
<kwd>MMFs</kwd>
<kwd>signalling molecules</kwd>
<kwd>
<italic>Streptomyces</italic>
sp. RK44</kwd>
<kwd>anticancer</kwd>
<kwd>antimalaria</kwd>
</kwd-group>
</article-meta>
</front>
<body>
<sec sec-type="intro" id="sec1-molecules-25-00460">
<title>1. Introduction</title>
<p>
<italic>Streptomyces</italic>
have been, for decades, one of the most prolific sources of pharmacologically-active compounds, contributing for more than half of the naturally-derived antibiotics that are in clinical use today, such as chloramphenicol (from
<italic>S. venezuelae</italic>
) [
<xref rid="B1-molecules-25-00460" ref-type="bibr">1</xref>
], fosfomycin (from
<italic>S. fradiae</italic>
) [
<xref rid="B2-molecules-25-00460" ref-type="bibr">2</xref>
], clavulanic acid (from
<italic>S. clavuligerus</italic>
) [
<xref rid="B3-molecules-25-00460" ref-type="bibr">3</xref>
], and avermectin (from
<italic>S. avermitilis</italic>
) [
<xref rid="B4-molecules-25-00460" ref-type="bibr">4</xref>
]. In our efforts to discover natural products, we have isolated a new bacterial strain,
<italic>Streptomyces</italic>
sp. RK44 from the underexplored areas of Kintampo waterfalls, Ghana, Africa [
<xref rid="B5-molecules-25-00460" ref-type="bibr">5</xref>
,
<xref rid="B6-molecules-25-00460" ref-type="bibr">6</xref>
].</p>
<p>Chemical profiling of the RK44 extract using high-resolution electrospray ionization mass spectrometry (HR-ESIMS) and Global Natural Product Social (GNPS) molecular network (MN) [
<xref rid="B7-molecules-25-00460" ref-type="bibr">7</xref>
] showed a cluster of low molecular weight metabolites with a characteristic 250 nm UV absorption, suggesting that they share a common chromophore skeleton. Database dereplication using AntiBase 2017 (WILEY) and other online databases (The Natural Products Atlas, ChemSpider) [
<xref rid="B8-molecules-25-00460" ref-type="bibr">8</xref>
,
<xref rid="B9-molecules-25-00460" ref-type="bibr">9</xref>
] revealed that these metabolites have not been previously described in the literature [
<xref rid="B10-molecules-25-00460" ref-type="bibr">10</xref>
,
<xref rid="B11-molecules-25-00460" ref-type="bibr">11</xref>
].</p>
<p>The isolation was carried out and afforded a new metabolite
<bold>1</bold>
(1.0 mg). Interpretation of the spectroscopic data demonstrated that
<bold>1</bold>
is 2-alkyl-4-hydroxymethylfuran-3-carboxamide (AHFA), a new methylenomycin furan (MMF) homolog which bears an amide moiety at C-3 instead of carboxylic acid [
<xref rid="B12-molecules-25-00460" ref-type="bibr">12</xref>
] in the former. MMFs are signalling molecules or autoregulators identified in 2008 in the model actinomycete
<italic>Streptomyces coelicolor</italic>
, which induce methylenomycin antibiotic production [
<xref rid="B10-molecules-25-00460" ref-type="bibr">10</xref>
]. Examples of the well-characterized autoregulators include acylhomoserine lactones (AHLs) in Gram-negative bacteria [
<xref rid="B13-molecules-25-00460" ref-type="bibr">13</xref>
] and γ-butyrolactones (GBLs) in Gram-positive bacteria of the genus
<italic>Streptomyces</italic>
[
<xref rid="B14-molecules-25-00460" ref-type="bibr">14</xref>
,
<xref rid="B15-molecules-25-00460" ref-type="bibr">15</xref>
].</p>
<p>Genome mining revealed that the furan-type autoregulators may be widespread in
<italic>Streptomyces</italic>
species [
<xref rid="B10-molecules-25-00460" ref-type="bibr">10</xref>
], however, only one class of MMFs has been identified to date [
<xref rid="B12-molecules-25-00460" ref-type="bibr">12</xref>
]. The discovery of this new class of 2-alkyl-4-hydroxymethylfuran-3-carboxamide signalling molecule, AHFA
<bold>1</bold>
further expanded the chemical space of the under-explored class of furan-based autoregulators, and the MMF biosynthetic machinery. Furthermore, the presence of AHFA
<bold>7</bold>
–
<bold>10</bold>
, bearing various alkyl substituents at C-2 of the furan ring was also detected by high-pressure liquid chromatography (HPLC)-Ultraviolet (UV)-HRESIMS-GNPS analyses, but they were not isolated due to their trace quantities in the extract.</p>
<p>Along with AHFA
<bold>1</bold>
, we also isolated known compounds, cyclo-(L-Pro-Gly)
<bold>2</bold>
, cyclo-(L-Pro-L-Phe)
<bold>3</bold>
, cyclo-(L-Pro-L-Val)
<bold>4</bold>
, cyclo-(L-Leu-Hyp)
<bold>5</bold>
, and deferoxamine E
<bold>6</bold>
. Moreover, the MN analysis also identified the clusters corresponding to diketopiperazines
<bold>2</bold>
–
<bold>5</bold>
, and siderophores
<bold>6</bold>
and
<bold>13</bold>
–
<bold>18</bold>
.</p>
</sec>
<sec sec-type="results" id="sec2-molecules-25-00460">
<title>2. Results and Discussion</title>
<p>A large-scale fermentation (6 L) of
<italic>Streptomyces</italic>
sp. RK44 in Modified Bennett’s broth [
<xref rid="B16-molecules-25-00460" ref-type="bibr">16</xref>
] was performed for seven days (28 °C, 180 rpm). Subsequently, Diaion
<sup>®</sup>
HP-20 (3 g/50 mL) was added to the culture broth and incubated overnight under the same culture conditions. The mixture was filtered under vacuum, after which the residue consisting of the mycelium and HP-20 resin was submerged in 100% methanol (3 × 500 mL) for 24 h. The methanol extract was then decanted and concentrated under reduced pressure to give a crude extract (5.8 g) which was then fractionated by solid-phase extraction (SPE) using Strata
<sup>®</sup>
C18-E to give six fractions (S1–S6).</p>
<p>Dereplication of SPE extracts of RK44 using GNPS and a survey of databases (e.g., Dictionary of Natural Products, AntiBase, The Natural Products Atlas) suggested the presence of potentially new metabolites cluster in fraction S3. Consequently, S3 was selected for further purification using semi-preparative reversed-phase HPLC to yield
<bold>1</bold>
(1.0 mg), along with a number of diketopiperazines
<bold>2</bold>
(1.2 mg)
<bold>, 3</bold>
(2.0 mg)
<bold>, 4</bold>
(2.1 mg)
<bold>, 5</bold>
(2.3 mg), and the known siderophore, deferoxamine E
<bold>6</bold>
(3.0 mg) (
<xref ref-type="fig" rid="molecules-25-00460-f001">Figure 1</xref>
).</p>
<sec id="sec2dot1-molecules-25-00460">
<title>2.1. Structure Elucidation</title>
<p>The structures of the diketopiperazines (DKPs), cyclo-(L-Pro-Gly)
<bold>2</bold>
, cyclo-(L-Pro-L-Phe)
<bold>3</bold>
, cyclo-(L-Pro-L-Val)
<bold>4</bold>
, and cyclo-(L-Leu-Hyp)
<bold>5</bold>
, were determined by comparison of the UV spectra, molecular formulae, and a series of Nuclear magnetic resonance (NMR) spectra with literature data [
<xref rid="B17-molecules-25-00460" ref-type="bibr">17</xref>
,
<xref rid="B18-molecules-25-00460" ref-type="bibr">18</xref>
,
<xref rid="B19-molecules-25-00460" ref-type="bibr">19</xref>
,
<xref rid="B20-molecules-25-00460" ref-type="bibr">20</xref>
,
<xref rid="B21-molecules-25-00460" ref-type="bibr">21</xref>
] (
<xref ref-type="app" rid="app1-molecules-25-00460">Figure S21–S24, Table S2</xref>
). The configuration of
<bold>2</bold>
–
<bold>5</bold>
were determined by advanced Marfey’s analysis, suggesting that all the proteogenic amino acids are in L-configuration (
<xref ref-type="app" rid="app1-molecules-25-00460">Table S4</xref>
). Compound
<bold>6</bold>
was identical to the reported siderophore, desferrioxamine E
<bold>6</bold>
[
<xref rid="B22-molecules-25-00460" ref-type="bibr">22</xref>
,
<xref rid="B23-molecules-25-00460" ref-type="bibr">23</xref>
,
<xref rid="B24-molecules-25-00460" ref-type="bibr">24</xref>
] (
<xref ref-type="app" rid="app1-molecules-25-00460">Figure S22, Table S3</xref>
).</p>
<p>Compound
<bold>1</bold>
was obtained as a yellow powder. The molecular formula of
<bold>1</bold>
(
<xref ref-type="fig" rid="molecules-25-00460-f001">Figure 1</xref>
) was established as C
<sub>10</sub>
H
<sub>15</sub>
NO
<sub>3</sub>
by High-Resolution Electrospray Ionization Mass Spectrometry (HR-ESIMS) (calculated [M + H]
<sup>+</sup>
= 198.1123; observed [M + H]
<sup>+</sup>
= 198.1125; ∆ = −0.5047 ppm), indicating 4 degrees of unsaturation (
<xref ref-type="app" rid="app1-molecules-25-00460">Figure S1</xref>
). The UV absorption maximum at 250 nm found in its spectrum is a characteristic feature of MMF molecules.</p>
<p>Analysis of the
<sup>1</sup>
H, HMBC, and HSQC spectra revealed the presence of 1 sp
<sup>2</sup>
methine, 4 methylenes, 1 methyl, and 4 quaternary carbons leading to the sub-formula C
<sub>10</sub>
H
<sub>12</sub>
(
<xref rid="molecules-25-00460-t001" ref-type="table">Table 1</xref>
). The
<sup>1</sup>
H-NMR spectrum in CD
<sub>3</sub>
OD contained signals for 12 of the 15 protons accounted by the molecular formula, suggesting three exchangeable protons. These protons were observed in the DMSO-
<italic>d</italic>
<sub>6</sub>
spectrum at δ
<sub>H</sub>
6.53 (NH
<sub>2</sub>
) and δ
<sub>H</sub>
4.05 (OH). The remaining oxygen atom and the
<sup>13</sup>
C chemical shifts (δ
<sub>C</sub>
162.1, 123.1, 139.1, 115.8), and the number of double bond equivalents suggested the presence of a furan core in the structure, which is supported by the heteronuclear multiple bond correlations (HMBC) from H-5 (δ
<sub>H</sub>
7.38, s) to C-2 (δ
<sub>C</sub>
162.1), C-3 (δ
<sub>C</sub>
115.8), and C-4 (δ
<sub>C</sub>
123.1).</p>
<p>Inspection of the
<sup>1</sup>
H-
<sup>1</sup>
H COSY data identified one spin system from H-1′to H-4′, indicative of a butyl alkyl chain. The cross peak from H
<sub>2</sub>
-1′ (δ
<sub>H</sub>
2.95, t) to C-2 (δ
<sub>C</sub>
162.1) established the connectivity of the butyl alkyl group to the furan framework. The observed downfield signal at δ
<sub>H</sub>
4.52 (H
<sub>2</sub>
-7, s) suggested a hydroxymethylene group, and it was placed at C-4 based on the strong HMBC from H-7 (δ
<sub>H</sub>
4.52) to C-3 (δ
<sub>C</sub>
115.8), C-4 (δ
<sub>C</sub>
123.1), and C-5 (δ
<sub>C</sub>
139.1). The carbonyl carbon at C-6 (δ
<sub>C</sub>
171.6) and the N-H signal (δ
<sub>H</sub>
6.53, 2H) obtained in DMSO-
<italic>d</italic>
<sub>6</sub>
accounted for an amide moiety, and its connectivity was assigned to the remaining quaternary carbon C-3 (δ
<sub>C</sub>
115.8) of the furan ring.</p>
<p>Final structural analysis of
<bold>1</bold>
was confirmed by comparison with the spectroscopic data reported for MMF4 [
<xref rid="B12-molecules-25-00460" ref-type="bibr">12</xref>
], which differs with
<bold>1</bold>
in the presence of a carboxylic acid in the former instead of the amide at position C-3. Compound
<bold>1</bold>
was therefore identified as 2-alkyl-4-hydroxymethylfruan carboxamide (AHFA).</p>
<p>MMFs share the common furan core in the structure, and the alkyl substituents at position C-2 of the ring can vary depending on which starter unit is incorporated during fatty acid biosynthesis [
<xref rid="B12-molecules-25-00460" ref-type="bibr">12</xref>
,
<xref rid="B25-molecules-25-00460" ref-type="bibr">25</xref>
]. Based on the HR ESIMS/GNPS analysis of the
<italic>Streptomyces</italic>
sp. RK44 extract, we have tentatively identified six AHFA
<bold>1</bold>
analogues,
<bold>7</bold>
–
<bold>12</bold>
, with various lengths in their carbon alkyl chains at C-2 of the furan ring (
<xref ref-type="app" rid="app1-molecules-25-00460">Figures S10–S16, Table S1</xref>
). However, they could not be isolated due to their presence in the extract in minute amounts. AHFA
<bold>7</bold>
–
<bold>12</bold>
clustered together in the molecular network (MN) signifying that they share a common structural motif evident in the presence of the furan framework (
<xref ref-type="app" rid="app1-molecules-25-00460">Figure S10</xref>
). Detailed analysis of the UV pattern, MS and MS
<sup>2</sup>
fragmentation data showed that they exhibit the characteristic UV absorption at 250 nm of MMFs, and the alkyl chain substitution at position C2 of the ring, analogous to the MMFs that have been reported previously [
<xref rid="B12-molecules-25-00460" ref-type="bibr">12</xref>
].</p>
<p>Further MN analysis also identified the clusters corresponding to the DKPs
<bold>2</bold>
–
<bold>5</bold>
, deferoxamines (DFO) B and E
<bold>6</bold>
and the 2.5kDa RIPP peptide (
<xref ref-type="app" rid="app1-molecules-25-00460">Figure S9</xref>
). The observed molecular ion peaks of
<bold>13</bold>
–
<bold>18</bold>
matched with the known ions in the GNPS library and they clustered together in the network, suggesting that they could be potentially new siderophores. Moreover, their fragmentation pathway were proposed based on the observed MS/MS data (
<xref ref-type="app" rid="app1-molecules-25-00460">Figure S20</xref>
). Characterization of the peptide is currently underway in our laboratory.</p>
</sec>
<sec id="sec2dot2-molecules-25-00460">
<title>2.2. Proposed MMF Biosynthetic Gene Cluster and Pathway</title>
<p>The biological function of AHFA
<bold>1</bold>
in the host cell is still unknown but is believed to be regulators of antibiotic biosynthesis in
<italic>Streptomyces</italic>
sp. RK44, analogous to the MMFs in
<italic>S. coelicolor</italic>
and GBLs in
<italic>Streptomyces</italic>
species [
<xref rid="B12-molecules-25-00460" ref-type="bibr">12</xref>
,
<xref rid="B25-molecules-25-00460" ref-type="bibr">25</xref>
]. Given the structural similarity of
<bold>1</bold>
with MMF4 [
<xref rid="B12-molecules-25-00460" ref-type="bibr">12</xref>
], we predicted that
<bold>1</bold>
originated from an analogous biosynthetic pathway of MMF4. In silico analysis of the annotated RK44 genome using antiSMASH 3.0 [
<xref rid="B26-molecules-25-00460" ref-type="bibr">26</xref>
] revealed one putative biosynthetic gene cluster, BGC (
<italic>ahfa</italic>
) that is likely to be involved in the biosynthesis of AHFA
<bold>1</bold>
. Pairwise comparison of the annotated proteins using BLAST [
<xref rid="B27-molecules-25-00460" ref-type="bibr">27</xref>
] and the sequence similarity network (SSN) [
<xref rid="B28-molecules-25-00460" ref-type="bibr">28</xref>
] between the
<italic>ahfa</italic>
cluster with the
<italic>mmf</italic>
BGC showed high amino acid identity, supporting its role in MMF homolog biosynthesis (
<xref ref-type="fig" rid="molecules-25-00460-f002">Figure 2</xref>
).</p>
<p>The
<italic>ahfa</italic>
gene cluster spans about 4.5 kb of genomic DNA and contains three biosynthetic genes (
<italic>ahfa</italic>
L,
<italic>ahfa</italic>
P,
<italic>ahfa</italic>
H) that are likely involved in the biosynthesis of AHFA
<bold>1</bold>
in
<italic>Streptomyces</italic>
sp. RK44 (
<xref rid="molecules-25-00460-t002" ref-type="table">Table 2</xref>
,
<xref ref-type="scheme" rid="molecules-25-00460-sch001">Scheme 1</xref>
). The incorporation of stereospecifically
<sup>13</sup>
C-labeled glycerols into the MMFs suggested that they are biosynthesized via a butenolide phosphate intermediate
<bold>22</bold>
[
<xref rid="B25-molecules-25-00460" ref-type="bibr">25</xref>
], derived from the MmfL-catalysed condensation of coenzyme A β-ketothioesters
<bold>19</bold>
in fatty acid biosynthesis with dihydroxyacetone (DHAP)
<bold>20</bold>
. The isotope-labelled studies indicated that the hydroxymethyl group in MMFs originated from the hydroxymethyl of DHAP, suggesting an analogous role of AhfaL to the AfsA in the biosynthesis of A-factor [
<xref rid="B29-molecules-25-00460" ref-type="bibr">29</xref>
], in contrary to the alternative roles proposed by Sello and colleagues (2009) [
<xref rid="B30-molecules-25-00460" ref-type="bibr">30</xref>
]. AhfaL which encodes for butenolide synthase in RK44 with 53% identity to
<italic>mmfL</italic>
and 42.0% similarity to
<italic>afsa</italic>
is proposed to catalyse a similar condensation reaction between 3-oxohexanoyl-thioester
<bold>19</bold>
and DHAP
<bold>20</bold>
to yield
<bold>21</bold>
, then
<bold>22</bold>
. AhfaP encoded for phosphatase and has 58% identity to MmfP is likely responsible for the dephosphorylation of butenolide
<bold>22</bold>
to form
<bold>23</bold>
, followed by rearrangement to
<bold>24</bold>
catalysed by the flavin-dependent monooxygenase, AhfaH. The formation of the furan ring in
<bold>1</bold>
and other AHFA analogues remains elusive.</p>
<p>Furthermore, two putative genes, ahfaR and ahfaS which encode for TetR/AcR transcriptional repressor showed high amino acid identities to MmfR and MmyR (46/62, WP_011039544.1; 62/75, WP_011039548.1) in
<italic>S. coelicolor</italic>
[
<xref rid="B31-molecules-25-00460" ref-type="bibr">31</xref>
], respectively, were likely responsible for the antibiotic regulation in RK44.</p>
<p>The deduced function of ahfa
<italic>L</italic>
,
<italic>H</italic>
,
<italic>P</italic>
genes, based on their homology to autoregulatory genes (
<italic>mmf</italic>
or
<italic>afs</italic>
) of known function, supports the structure and the probable role of AHFA
<bold>1</bold>
as a signalling molecule.</p>
</sec>
<sec id="sec2dot3-molecules-25-00460">
<title>2.3. Biological Test</title>
<p>AHFA
<bold>1</bold>
inhibited proliferation and viability of human A2058 melanoma cells and induced anoikis (EC
<sub>50</sub>
= 89.6 µM) (
<xref ref-type="fig" rid="molecules-25-00460-f003">Figure 3</xref>
B) compared to control (treated with culture media alone,
<xref ref-type="fig" rid="molecules-25-00460-f003">Figure 3</xref>
C). It is worth noting that, although weak, this activity is the first time to be reported amongst MMFs (
<xref ref-type="app" rid="app1-molecules-25-00460">Figure S23</xref>
). Compounds
<bold>2</bold>
–
<bold>6</bold>
did not display any bioactivity at the highest concentration tested (50 µM).</p>
<p>Compounds
<bold>1</bold>
–
<bold>6</bold>
were also investigated for their anti-plasmodial activities against
<italic>Plasmodium falciparum</italic>
3D7. Only
<bold>6</bold>
showed potent antimalarial activity (IC
<sub>50</sub>
= 1.08 µM), and
<bold>1</bold>
–
<bold>5</bold>
did not display any bioactivity at the highest concentration tested (50 µM). The activity of
<bold>6</bold>
may result from the strong chelation of DFO-E
<bold>6</bold>
with iron from the culture medium of
<italic>P. falciparum</italic>
, causing iron deficit and finally cell death [
<xref rid="B32-molecules-25-00460" ref-type="bibr">32</xref>
]. This observation was consistent with the reported antiplasmodial activities of siderophores in literature [
<xref rid="B33-molecules-25-00460" ref-type="bibr">33</xref>
,
<xref rid="B34-molecules-25-00460" ref-type="bibr">34</xref>
,
<xref rid="B35-molecules-25-00460" ref-type="bibr">35</xref>
,
<xref rid="B36-molecules-25-00460" ref-type="bibr">36</xref>
].</p>
<p>On the other hand, there are no significant antimicrobial activities observed in
<bold>1</bold>
–
<bold>6</bold>
against the Gram-negative pathogens,
<italic>Pseudomonas aeruginosa</italic>
ATCC 27853 and
<italic>Escherichia coli</italic>
ATCC 25922 at concentrations between 0–50 µg/mL.</p>
</sec>
</sec>
<sec id="sec3-molecules-25-00460">
<title>3. Materials and Methods</title>
<sec id="sec3dot1-molecules-25-00460">
<title>3.1. Fermentation</title>
<p>
<italic>Streptomyces</italic>
sp. RK44 was isolated from the soil near Kintampo waterfall, Ghana, Africa. The soil isolate was streaked on an ISP2 agar plate (yeast extract 4 g, malt extract 10 g, glucose 4 g, 15 g agar, in 1L H2O) to get pure single colonies. One single colony was inoculated into 50 mL of Modified Bennett’s liquid medium (glycerol 10.0 g, Oxoid yeast extract 1.0 g, Bacto-Casitone 2.0, Lab-Lemco 0.8 g in 1000 mL MilliQ H
<sub>2</sub>
O), and incubated for three days at 28 °C with shaking at 180 rpm (Incu-shake FL16-2). This seed culture was used to inoculate 6.0 L of MB broth (1:100) in 12 baffled flasks (Corning
<sup>TM</sup>
polycarbonate flasks), each containing autoclaved MB medium (500 mL) and plugged with Fisherbrand™ polyurethane foam stoppers (Fisher Scientific, UK). The cultures were fermented for seven days under the same condition as the seed culture. On day 7, Diaion
<sup>®</sup>
HP-20 (3 g/50 mL) was added to the fermentation culture under sterile conditions. The flasks were left in the same shaking temperature and conditions for 16–22 h. The culture broth was filtered under vacuum (Buchi pump V100, UK), and the HP-20 resin was washed with MilliQ water and extracted thrice with 100% methanol (Fisher Chemical HPLC grade). All the methanol extracts were combined, concentrated under reduced pressure (Buchi Rotavapor R200, BUCHI, UK), and subjected to High-resolution Electrospray Ionization Liquid Chromatography Mass Spectrometry (HRESI-LC-MS, Thermo Scientific, UK) analysis.</p>
</sec>
<sec id="sec3dot2-molecules-25-00460">
<title>3.2. Molecular Network Analysis</title>
<p>MSConvert software (3.0, Proteowizard, CA, US) was used to convert LCMS.RAW data to the mzXML format files. MZmine was used to preprocess the data and exported to the GNPS platform for molecular networking data analysis [
<xref rid="B37-molecules-25-00460" ref-type="bibr">37</xref>
]. The GNPS analysis was achieved through the GNPS data analysis workflow using the spectral clustering algorithm [
<xref rid="B38-molecules-25-00460" ref-type="bibr">38</xref>
]. Data analysis was performed using the following settings: parent mass tolerance 0.02 Da, ion tolerance 0.02 Da, minimum pairs cosine 0.7, minimum matched peaks 6, network TopK 10, minimum cluster size 2, and maximum connected component size 100. The spectral library matching was performed with a similar cosine threshold and minimum matched peaks. The spectral networks were imported into Cytoscape 3.6.1 and visualized using the force-directed layout [
<xref rid="B39-molecules-25-00460" ref-type="bibr">39</xref>
].</p>
</sec>
<sec id="sec3dot3-molecules-25-00460">
<title>3.3. Spectroscopic Analysis</title>
<p>HR-ESI-LC-MS was obtained using an LTQ Orbitrap LC-MS system (Thermo Scientific, UK) coupled to a Thermo Instrument HPLC system (Accela PDA detector, Accela PDA autosampler and Accela Pump) on a positive ESI mode (30,000), MS/MS resolution 7500, C18 (Sunfire 150 × 46 mm column). 0.1% formic acid in water and 0.1% formic acid in acetonitrile was used for reverse-phase separation using a gradient from 0–100% in 25 min. The instrument parameters were set as following: Capillary voltage 45 V, spray voltage 4.5 kV, capillary temperature 200 °C, auxiliary gas flow rate 10–20 arbitrary units, sheath gas flow rate 5 arbitrary units, mass range 150–2000 amu (maximum resolution 30,000×), MS scan 150–2000Da coupled with an automated full dependent MS-MS scan.</p>
<p>1D and 2D NMR data were obtained on a Bruker AVANCE III HD 600 MHz (Ascend
<sup>TM</sup>
14.1 Tesla, UK) with Prodigy TCI
<sup>TM</sup>
cryoprobe at 298 K in DMSO-
<italic>d</italic>
<sub>6</sub>
and CD
<sub>3</sub>
OD (Goss Scientific). Trimethylsilane (TMS) was used as an internal standard.</p>
</sec>
<sec id="sec3dot4-molecules-25-00460">
<title>3.4. Fractionation of the Extract</title>
<p>Fractionation of the crude methanol extract was achieved by using Strata
<sup>®</sup>
C18-E solid-phase extraction (SPE) (55 µm, 70 Å, 20 g/60 mL) cartridges. The SPE column was initially washed with two column volumes (CV) of methanol and MilliQ water separately, and then, the crude sample was loaded onto the column. The column was then eluted stepwise with solvent mixtures of decreasing polarity (8CV/solvent mixture): Milli-Q H
<sub>2</sub>
O, 25% MeOH, 50% MeOH, 75% MeOH, 100% MeOH, and 100% MeOH with 0.05% trifluoroacetic acid (Acros Organics). The eluents were collected separately and labelled as fractions S1–S6. All the fractions were concentrated under reduced pressure (Buchi Rotavapor R200) and subjected to HR-ESI-MS analysis.</p>
<p>Mass spectrometry (MS) analysis was carried out in all the fractions (S1–S6) to target the MMF signalling molecules. Analysis of the HRESI-LC-MS data of fraction S3 revealed seven resolved peaks with [M + H]
<sup>+</sup>
ions at m/z 184.0967, 198.1123, 212.128, respectively. Dereplication of these masses was achieved using AntiBase (2017), indicating that these molecules were previously unreported but might share a similar furan core as MMF molecules. Thus, fraction S3 was selected for further fractionation by reversed-phase semi-prep (C18 ACE 10 µM 10 × 250 mm column) HPLC (Agilent 1260 Infinity). The purification was carried out using a linear gradient from 20% H
<sub>2</sub>
O: MeOH (95:5) to 100% MeOH for 28 min with a solvent flow rate of 1.5 mL/min, to yield AHFA
<bold>1</bold>
(1.0 mg). Six other furan derivatives,
<bold>7</bold>
–
<bold>12</bold>
were identified in the same fraction by HRESI-LC-MS and molecular network analyses (
<xref ref-type="app" rid="app1-molecules-25-00460">Figure S9, Table S1</xref>
). However, these molecules could not be isolated due to their presence in trace quantities in the extract. Compound
<bold>2</bold>
–
<bold>6</bold>
were isolated in the fraction S2, using a linear gradient from 10% H2O: MeOH (95:5) to 100% MeOH for 28 min with a solvent flow rate of 1.5 mL/min.</p>
<p>Along with
<bold>1</bold>
, we also isolated cyclo-(L-Pro-Gly)
<bold>2</bold>
, cyclo-(L-Pro-L-Phe)
<bold>3</bold>
, cyclo-(L-Pro-L-Val)
<bold>4</bold>
, cyclo-(L-Leu-Hyp)
<bold>5</bold>
, and deferoxamine E
<bold>6</bold>
.</p>
<p>AHFA
<bold>1</bold>
: 1.0mg; pale yellow powder. UV (CH
<sub>3</sub>
OH): 250 nm;
<sup>1</sup>
H,
<sup>13</sup>
C-NMR data, see
<xref rid="molecules-25-00460-t001" ref-type="table">Table 1</xref>
; HRESIMS (positive mode)
<italic>m</italic>
/
<italic>z</italic>
calculated [M + H]
<sup>+</sup>
= 198.1125; observed [M + H]
<sup>+</sup>
= 198.1123; ∆ = −0.5050 ppm.</p>
<p>cyclo-(L-Pro-Gly)
<bold>2</bold>
: 1.2 mg; white solid;
<sup>1</sup>
H,
<sup>13</sup>
C-NMR data, see
<xref ref-type="app" rid="app1-molecules-25-00460">Figure S21, Table S2</xref>
; HRESIMS (positive mode)
<italic>m</italic>
/
<italic>z</italic>
calculated [M + H]
<sup>+</sup>
= 155.0815; observed [M + H]
<sup>+</sup>
= 155.0821; ∆ = 2.870 ppm.</p>
<p>cyclo-(L-Pro-L-Phe)
<bold>3</bold>
: 2.0 mg; pale yellow solid;
<sup>1</sup>
H,
<sup>13</sup>
C-NMR data, see
<xref ref-type="app" rid="app1-molecules-25-00460">Figure S22, Table S2</xref>
; [α]
<sup>25</sup>
<sub>D</sub>
= −17.2 (
<italic>c</italic>
1.0, MeOH); HRESIMS (positive mode)
<italic>m/z</italic>
calculated [M + H]
<sup>+</sup>
= 245.1285; observed [M + H]
<sup>+</sup>
= 245.1276; ∆ = −2.631 ppm.</p>
<p>cyclo-(L-Pro-L-Val)
<bold>4</bold>
: 2.1 mg; pale yellow solid;
<sup>1</sup>
H,
<sup>13</sup>
C-NMR data, see
<xref ref-type="app" rid="app1-molecules-25-00460">Figure S23, Table S2</xref>
; [α]
<sup>25</sup>
<sub>D</sub>
= −31.0 (
<italic>c</italic>
1.0, MeOH); HRESIMS (positive mode)
<italic>m</italic>
/
<italic>z</italic>
calculated [M + H]
<sup>+</sup>
= 197.1285; observed [M + H]
<sup>+</sup>
= 197.1284; ∆ = −0.5070 ppm.</p>
<p>cyclo-(L-Leu-Hyp)
<bold>5</bold>
: 2.3 mg; yellow solid;
<sup>1</sup>
H,
<sup>13</sup>
C-NMR data, see
<xref ref-type="app" rid="app1-molecules-25-00460">Figure S24, Table S2</xref>
; [α]
<sup>25</sup>
<sub>D</sub>
= −11.6 (
<italic>c</italic>
1.0, MeOH); HRESIMS (positive mode)
<italic>m/z</italic>
calculated [M + H]
<sup>+</sup>
= 227.1390; observed [M + H]
<sup>+</sup>
= 227.1392; ∆ = −0.7040 ppm.</p>
<p>Deferoxamine E
<bold>6</bold>
: 3.0 mg; pale yellow solid;
<sup>1</sup>
H,
<sup>13</sup>
C-NMR data, see
<xref ref-type="app" rid="app1-molecules-25-00460">Figure S25, Table S3</xref>
; HRESIMS (positive mode)
<italic>m</italic>
/
<italic>z</italic>
calculated [M + H]
<sup>+</sup>
= 601.3356; observed [M + H]
<sup>+</sup>
= 601.3350; ∆ = −1.031 ppm.</p>
</sec>
<sec id="sec3dot5-molecules-25-00460">
<title>3.5. Advanced Marfey’s Experiment</title>
<p>Compounds
<bold>2</bold>
–
<bold>5</bold>
(0.5mg) were hydrolysed in 6 N HCl (1 mL) for 17 h at 115 °C. The hydrolysate was evaporated to dryness, dissolved in H
<sub>2</sub>
O (100 µL), and then, treated with 1 M NaHCO
<sub>3</sub>
(20 µL), and FDLA, fluorodinitrophenyl-5-L-leucine amide (1% solution in acetone, 100 µL). The mixture was incubated at 40 °C for 1 h. The reaction was neutralized by addition of 2 N HCl (20 µL) and evaporated to dryness at 40 °C under a stream of dry N
<sub>2</sub>
. The residue was dissolved in CH
<sub>3</sub>
OH (500 µL) and filtered (0.45 μm PTFE) prior to HPLC-Diode Array Detection (DAD) analysis. The separation was carried out using gradient elution CH
<sub>3</sub>
CN/H
<sub>2</sub>
O with 0.1% TFA (from 0% to 100% for 30 min, flow rate 1.0 mL/min, UV detection λ
<sub>max</sub>
340 nm).</p>
<p>The standard amino acids were derivatized with FDLA and analyzed by HPLC-DAD in the same manner as the test compounds.</p>
</sec>
<sec id="sec3dot6-molecules-25-00460">
<title>3.6. Genome Sequencing of Streptomyces sp. RK44</title>
<p>The genome sequencing of
<italic>Streptomyces</italic>
sp. RK44 and the sequencing assembly service were provided by BGI-Shenzhen, China. A 300 bp paired-end genomic library of RK44 was prepared for Illumina sequencing. A total of 11,820,095 bp were obtained and assembled by SOAP denovo software. The assembled genome was submitted to the RAST server for annotation [
<xref rid="B40-molecules-25-00460" ref-type="bibr">40</xref>
]. The open reading frames (ORFs) of the
<italic>ahfa</italic>
gene cluster was identified using the key enzymes encoded in the known
<italic>mmf</italic>
gene cluster as a sequence query. The 16s rDNA sequences and the
<italic>ahfa</italic>
cluster has been deposited in the NCBI (MN906804).</p>
<p>Based on the partial 16s DNA gene sequence analysis it was identified that the strain belongs to the class
<italic>Streptomyces</italic>
and was most closely related to three strains with 82.49% sequence similarity:
<italic>Streptomyces hoynatensis</italic>
S1412,
<italic>Streptomyces carpaticus</italic>
NRRL B-16359,
<italic>Streptomyces yeochonensis</italic>
NBRC 100782. The strain formed a well-separated clade in the genus
<italic>Streptomyces</italic>
(
<xref ref-type="fig" rid="molecules-25-00460-f004">Figure 4</xref>
) based on the 16S rRNA gene analysis, indicating that
<italic>Streptomyces</italic>
sp. RK44
<italic>is a</italic>
new
<italic>Streptomyces</italic>
species (MEGA 7, Neighbor-Joining method) [
<xref rid="B41-molecules-25-00460" ref-type="bibr">41</xref>
,
<xref rid="B42-molecules-25-00460" ref-type="bibr">42</xref>
]. The optimum pH for growth was determined to be 7.2. The DNA G+C content of the strain was determined to be 71.4 mol%.</p>
</sec>
<sec id="sec3dot7-molecules-25-00460">
<title>3.7. Sequence Similarity Network</title>
<p>The sequence similarity network (
<xref ref-type="fig" rid="molecules-25-00460-f002">Figure 2</xref>
) of the biosynthetic gene clusters of
<italic>Streptomyces</italic>
sp. Rk44 and
<italic>Streptomyces coelicolor</italic>
A3(2) was constructed by all-to-all BLASTP comparison of sequences found in strains containing essential biosynthetic genes involved in the MMF and AHFA biosynthesis. Each node represents a gene and each edge represents the BLASTP pairwise comparison (E-value > 1 × 10
<sup>−10</sup>
) between two gene sequences. The results generated were visualized using Cytoscape 3.6.1. The genes,
<italic>mmfL</italic>
,
<italic>H</italic>
,
<italic>P</italic>
, are coloured with red, green, and blue, respectively. Other genes in the clusters were coloured with grey [
<xref rid="B28-molecules-25-00460" ref-type="bibr">28</xref>
].</p>
</sec>
<sec id="sec3dot8-molecules-25-00460">
<title>3.8. Anti-Proliferative/Cytotoxicity Test</title>
<p>The anti-proliferative activity of AHFA
<bold>1</bold>
was tested on the human melanoma A2058 cancer cell line (American Type Culture Collection (ATCC) CRL-11147
<sup>TM</sup>
, Manassas, VA, USA). Cell lines were seeded in 96-well-microtitre plates (Nunc, Thermo Fisher Scientific, NY, USA) at 2000 cells/well in Dulbecco’s Modified Eagle Medium (DMEM, Thermo Fisher Scientific, USA) with fetal bovine serum (10%, FBS, Sigma Aldrich, USA) and gentamicin (10 µg/mL, Sigma Aldrich, USA). Cells were grown at 37 °C in a humidified atmosphere of 5% CO
<sub>2</sub>
and maintained at low passage.</p>
<p>Toxicity assay was tested on the lung normal cell (ATCC CCL-171).Cell lines were seeded in 96-well-microtitre plates (Nunc, Thermo Fisher Scientific, CA, USA) at 4000 cells/well in DMEM with FBS (10%) and gentamicin (10 µg/mL). Cells were grown at 37 °C in a humidified atmosphere of 5% CO
<sub>2</sub>
and maintained at low passage.</p>
<p>Cells were incubated for 24 h before AHFA
<bold>1</bold>
was added and thereafter incubated for 72 h. Cell viability was determined by a colorimetric 3-(4,5-dimethylthiazol-2-yl)-5-(3 carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay. At the end of the exposure time, 10 µL Cell Titer 96
<sup>®</sup>
Aqueous One Solution Reagent (Promega, Madison, WI, USA) was added to each well. Results were measured after 1 h at 485 nm. The dose-dependent response of AHFA
<bold>1</bold>
(100 ng/mL, 1, 2.5, 5, 10, 12.5, 25, and 50 µg/mL) was tested in triplicates.</p>
</sec>
<sec id="sec3dot9-molecules-25-00460">
<title>3.9. Antibacterial Assay</title>
<p>Minimum inhibitory concentrations (MIC) were determined using a conventional broth dilution assay in accordance with standards recommended by the National Committee for Clinical Laboratory Standards (NCCLS) [
<xref rid="B43-molecules-25-00460" ref-type="bibr">43</xref>
]. Gram-negative bacteria
<italic>Escherichia coli</italic>
(ATCC 25922) and
<italic>Pseudomonas aeruginosa</italic>
(ATCC 27853) were used as test organisms. All bacteria were cultured in Mueller–Hinton broth. The assays were performed in 96-well plates (Nunc, Thermo Fisher Scientific, NY, USA), wherein a 50 µL suspension (log phase) of actively growing bacteria was incubated overnight at 37 °C and then treated with 50 µL of the test extract (final concentration of 50 μg/mL, for the three biological triplicates). The negative control comprised the growth media and Milli-Q water, while the positive control consisted of the bacteria plus Milli-Q water. The absorbance was recorded after 24 h (OD
<sub>600</sub>
) in a Victor3 multilabel plate reader. The growth medium appeared clear in wells where the test compound prevented the growth or killed the bacteria; otherwise, it was cloudy. Activity threshold was set below 0.05 (OD
<sub>600</sub>
).</p>
</sec>
<sec id="sec3dot10-molecules-25-00460">
<title>3.10. Plasmodium Falciparum 3D7 Lactate Dehydrogenase Assay</title>
<p>The antiplasmodial activities of
<bold>1</bold>
–
<bold>6</bold>
were assessed by lactate dehydrogenase assay using
<italic>Plasmodium falciparum</italic>
3D7 as the test organism. The assay was performed according to the method previously described by Pérez-Moreno et al., 2016 [
<xref rid="B36-molecules-25-00460" ref-type="bibr">36</xref>
], in triplicate using a sixteen points dose-response curve (1⁄2 serial dilutions) with concentrations ranging from 50 μM to 1.5 nM to determine the IC
<sub>50</sub>
of the pure compounds. Chloroquine was used as the standard reference.</p>
</sec>
</sec>
<sec sec-type="conclusions" id="sec4-molecules-25-00460">
<title>4. Conclusions</title>
<p>Herein, we report the discovery of AHFA
<bold>1</bold>
from the novel soil bacterium
<italic>Streptomyces</italic>
sp. RK44. The structure of
<bold>1</bold>
was deduced by analysis of the HRESIMS, UV, 1D, and 2D NMR, and identified as a new AHFA-type natural product. Seven AHFA analogues,
<bold>7</bold>
–
<bold>12</bold>
and siderophores
<bold>13</bold>
–
<bold>18</bold>
were tentatively identified in the extract of RK44 by HRESIMS and GNPS molecular network analyses. A putative AHFA biosynthetic pathway was proposed for
<bold>1</bold>
. AHFA
<bold>1</bold>
displayed antiproliferative activity against melanoma A2058 cells (EC
<sub>50</sub>
= 89.6 µM). Albeit weak, this represents the first report of such activity amongst MMF molecules. Five other known metabolites, cyclo-(L-Pro-Gly)
<bold>2</bold>
, cyclo-(L-Pro-L-Phe)
<bold>3</bold>
, cyclo-(L-Pro-L-Val)
<bold>4</bold>
, cyclo-(L-Leu-Hyp)
<bold>5</bold>
, and deferoxamine E
<bold>6</bold>
were isolated and structurally characterized, one of which, DFO-E
<bold>6</bold>
displayed potent activity against
<italic>P. falciparum</italic>
3D7 (IC
<sub>50</sub>
= 1.08 µM).</p>
</sec>
</body>
<back>
<fn-group>
<fn>
<p>
<bold>Sample Availability:</bold>
Samples of the compounds are not available from the authors.</p>
</fn>
</fn-group>
<app-group>
<app id="app1-molecules-25-00460">
<title>Supplementary Materials</title>
<supplementary-material content-type="local-data" id="molecules-25-00460-s001">
<media xlink:href="molecules-25-00460-s001.pdf">
<caption>
<p>Click here for additional data file.</p>
</caption>
</media>
</supplementary-material>
<p>The supplementary materials are available online.</p>
</app>
</app-group>
<notes>
<title>Author Contributions</title>
<p>Q.F., R.E., F.A., G.P.-M., F.R., J.H., L.W., F.M., H.D. formal analysis and investigation. H.D., K.K., J.H.A. funding acquisition and methodology. Q.F., F.M., H.D. writing original draft. H.D., J.H.A., F.R., K.K. review and editing. H.D. supervision and project administration. All authors have read and agreed to the published version of the manuscript.</p>
</notes>
<notes>
<title>Funding</title>
<p>Q.F. is grateful to the University of Aberdeen Elphinstone Scholarship and Scottish Funding Council/ScotCHEM for financial support through the PEER/PERCE Funding. FM thanks the University of the Philippines for the Faculty, Reps and Staff Development Program (FRAS DP) for the PhD grant fellowship. HD and KK thank the financial supports of Leverhulme Trust-Royal Society Africa award (AA090088) and the jointly funded UK Medical Research Council-UK Department for International Development (MRC/DFID) Concordat agreement African Research Leaders Award (MR/S00520X/1).</p>
</notes>
<notes notes-type="COI-statement">
<title>Conflicts of Interest</title>
<p>The authors declare no conflict of interest.</p>
</notes>
<ref-list>
<title>References</title>
<ref id="B1-molecules-25-00460">
<label>1.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Eliakim-Raz</surname>
<given-names>N.</given-names>
</name>
<name>
<surname>Lador</surname>
<given-names>A.</given-names>
</name>
<name>
<surname>Leibovici-Weissman</surname>
<given-names>Y.</given-names>
</name>
<name>
<surname>Elbaz</surname>
<given-names>M.</given-names>
</name>
<name>
<surname>Paul</surname>
<given-names>M.</given-names>
</name>
<name>
<surname>Leibovici</surname>
<given-names>L.</given-names>
</name>
</person-group>
<article-title>Efficacy and Safety of Chloramphenicol: Joining the Revival of old Antibiotics? Systematic Review and Meta-Analysis of Randomized Controlled Trials</article-title>
<source>J. Antimicrob. Chemother.</source>
<year>2014</year>
<volume>70</volume>
<fpage>979</fpage>
<lpage>996</lpage>
<pub-id pub-id-type="doi">10.1093/jac/dku530</pub-id>
</element-citation>
</ref>
<ref id="B2-molecules-25-00460">
<label>2.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Falagas</surname>
<given-names>M.E.</given-names>
</name>
<name>
<surname>Vouloumanou</surname>
<given-names>E.K.</given-names>
</name>
<name>
<surname>Samonis</surname>
<given-names>G.</given-names>
</name>
<name>
<surname>Vardakas</surname>
<given-names>K.Z.</given-names>
</name>
</person-group>
<article-title>Fosfomycin—Microbiology Review</article-title>
<source>Clin. Microbiol. Rev.</source>
<year>2016</year>
<volume>29</volume>
<fpage>321</fpage>
<lpage>347</lpage>
<pub-id pub-id-type="doi">10.1128/CMR.00068-15</pub-id>
<pub-id pub-id-type="pmid">26960938</pub-id>
</element-citation>
</ref>
<ref id="B3-molecules-25-00460">
<label>3.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Vons</surname>
<given-names>C.</given-names>
</name>
<name>
<surname>Barry</surname>
<given-names>C.</given-names>
</name>
<name>
<surname>Maitre</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Pautrat</surname>
<given-names>K.</given-names>
</name>
<name>
<surname>Leconte</surname>
<given-names>M.</given-names>
</name>
<name>
<surname>Costaglioli</surname>
<given-names>B.</given-names>
</name>
<name>
<surname>Karoui</surname>
<given-names>M.</given-names>
</name>
<name>
<surname>Alves</surname>
<given-names>A.</given-names>
</name>
<name>
<surname>Dousset</surname>
<given-names>B.</given-names>
</name>
<name>
<surname>Valleur</surname>
<given-names>P.</given-names>
</name>
<etal></etal>
</person-group>
<article-title>Amoxicillin Plus Clavulanic Acid Versus Appendicectomy for Treatment of Acute Uncomplicated Appendicitis: An Open-Label, Non-Inferiority, Randomised Controlled Trial</article-title>
<source>Lancet</source>
<year>2011</year>
<volume>377</volume>
<fpage>1573</fpage>
<lpage>1579</lpage>
<pub-id pub-id-type="doi">10.1016/S0140-6736(11)60410-8</pub-id>
<pub-id pub-id-type="pmid">21550483</pub-id>
</element-citation>
</ref>
<ref id="B4-molecules-25-00460">
<label>4.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Kitani</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Miyamoto</surname>
<given-names>K.T.</given-names>
</name>
<name>
<surname>Takamatsu</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Herawati</surname>
<given-names>E.</given-names>
</name>
<name>
<surname>Iguchi</surname>
<given-names>H.</given-names>
</name>
<name>
<surname>Nishitomi</surname>
<given-names>K.</given-names>
</name>
<name>
<surname>Uchida</surname>
<given-names>M.</given-names>
</name>
<name>
<surname>Nagamitsu</surname>
<given-names>T.</given-names>
</name>
<name>
<surname>Omura</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Ikeda</surname>
<given-names>H.</given-names>
</name>
<etal></etal>
</person-group>
<article-title>Avenolide, a Streptomyces Hormone Controlling Antibiotic Production in Streptomyces Avermitilis</article-title>
<source>Proc. Natl. Acad. Sci. USA</source>
<year>2011</year>
<volume>108</volume>
<fpage>16410</fpage>
<lpage>16415</lpage>
<pub-id pub-id-type="doi">10.1073/pnas.1113908108</pub-id>
<pub-id pub-id-type="pmid">21930904</pub-id>
</element-citation>
</ref>
<ref id="B5-molecules-25-00460">
<label>5.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Maglangit</surname>
<given-names>F.</given-names>
</name>
<name>
<surname>Fang</surname>
<given-names>Q.</given-names>
</name>
<name>
<surname>Leman</surname>
<given-names>V.</given-names>
</name>
<name>
<surname>Soldatou</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Ebel</surname>
<given-names>R.</given-names>
</name>
<name>
<surname>Deng</surname>
<given-names>H.</given-names>
</name>
</person-group>
<article-title>Accramycin A, a New Aromatic Polyketide, from the Soil Bacterium, Streptomyces sp. MA37</article-title>
<source>Molecules</source>
<year>2019</year>
<volume>24</volume>
<elocation-id>3384</elocation-id>
<pub-id pub-id-type="doi">10.3390/molecules24183384</pub-id>
</element-citation>
</ref>
<ref id="B6-molecules-25-00460">
<label>6.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Maglangit</surname>
<given-names>F.</given-names>
</name>
<name>
<surname>Fang</surname>
<given-names>Q.</given-names>
</name>
<name>
<surname>Kyeremeh</surname>
<given-names>K.</given-names>
</name>
<name>
<surname>Sternberg</surname>
<given-names>J.M.</given-names>
</name>
<name>
<surname>Ebel</surname>
<given-names>R.</given-names>
</name>
<name>
<surname>Deng</surname>
<given-names>H.</given-names>
</name>
</person-group>
<article-title>A Co-Culturing Approach Enables Discovery and Biosynthesis of a Bioactive Indole Alkaloid Metabolite</article-title>
<source>Molecules</source>
<year>2020</year>
<volume>25</volume>
<elocation-id>256</elocation-id>
<pub-id pub-id-type="doi">10.3390/molecules25020256</pub-id>
<pub-id pub-id-type="pmid">31936318</pub-id>
</element-citation>
</ref>
<ref id="B7-molecules-25-00460">
<label>7.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Wang</surname>
<given-names>M.</given-names>
</name>
<name>
<surname>Carver</surname>
<given-names>J.J.</given-names>
</name>
<name>
<surname>Phelan</surname>
<given-names>V.V.</given-names>
</name>
<name>
<surname>Sanchez</surname>
<given-names>L.M.</given-names>
</name>
<name>
<surname>Garg</surname>
<given-names>N.</given-names>
</name>
<name>
<surname>Peng</surname>
<given-names>Y.</given-names>
</name>
<name>
<surname>Nguyen</surname>
<given-names>D.D.</given-names>
</name>
<name>
<surname>Watrous</surname>
<given-names>J.</given-names>
</name>
<name>
<surname>Kapono</surname>
<given-names>C.A.</given-names>
</name>
<name>
<surname>Luzzatto-Knaan</surname>
<given-names>T.</given-names>
</name>
<etal></etal>
</person-group>
<article-title>Sharing and community curation of mass spectrometry data with Global Natural Products Social Molecular Networking</article-title>
<source>Nat. Biotechnol.</source>
<year>2016</year>
<volume>34</volume>
<fpage>828</fpage>
<lpage>837</lpage>
<pub-id pub-id-type="doi">10.1038/nbt.3597</pub-id>
<pub-id pub-id-type="pmid">27504778</pub-id>
</element-citation>
</ref>
<ref id="B8-molecules-25-00460">
<label>8.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Santen</surname>
<given-names>J.</given-names>
</name>
<name>
<surname>Van</surname>
<given-names>A.</given-names>
</name>
<name>
<surname>Jacob</surname>
<given-names>G.</given-names>
</name>
<name>
<surname>Singh</surname>
<given-names>A.L.</given-names>
</name>
<name>
<surname>Aniebok</surname>
<given-names>V.</given-names>
</name>
<name>
<surname>Balunas</surname>
<given-names>M.J.</given-names>
</name>
<name>
<surname>Bunsko</surname>
<given-names>D.</given-names>
</name>
<name>
<surname>Neto</surname>
<given-names>F.C.</given-names>
</name>
<name>
<surname>Castaño-Espriu</surname>
<given-names>L.</given-names>
</name>
<name>
<surname>Chang</surname>
<given-names>C.</given-names>
</name>
<etal></etal>
</person-group>
<article-title>The Natural Products Atlas: An Open Access Knowledge Base for Microbial Natural Products Discovery</article-title>
<source>ACS Cent. Sci.</source>
<year>2019</year>
<pub-id pub-id-type="doi">10.1021/acscentsci.9b00806</pub-id>
<pub-id pub-id-type="pmid">31807684</pub-id>
</element-citation>
</ref>
<ref id="B9-molecules-25-00460">
<label>9.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Pence</surname>
<given-names>H.E.</given-names>
</name>
<name>
<surname>Williams</surname>
<given-names>A.</given-names>
</name>
</person-group>
<article-title>Chemspider: An online chemical information resource</article-title>
<source>J. Chem. Educ.</source>
<year>2010</year>
<volume>87</volume>
<fpage>1123</fpage>
<lpage>1124</lpage>
<pub-id pub-id-type="doi">10.1021/ed100697w</pub-id>
</element-citation>
</ref>
<ref id="B10-molecules-25-00460">
<label>10.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Ito</surname>
<given-names>T.</given-names>
</name>
<name>
<surname>Masubuchi</surname>
<given-names>M.</given-names>
</name>
</person-group>
<article-title>Dereplication of Microbial Extracts and Related Analytical Technologies</article-title>
<source>J. Antibiot. (Tokyo)</source>
<year>2014</year>
<volume>67</volume>
<fpage>353</fpage>
<lpage>360</lpage>
<pub-id pub-id-type="doi">10.1038/ja.2014.12</pub-id>
<pub-id pub-id-type="pmid">24569671</pub-id>
</element-citation>
</ref>
<ref id="B11-molecules-25-00460">
<label>11.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Crüsemann</surname>
<given-names>M.</given-names>
</name>
<name>
<surname>O’Neill</surname>
<given-names>E.C.</given-names>
</name>
<name>
<surname>Larson</surname>
<given-names>C.B.</given-names>
</name>
<name>
<surname>Melnik</surname>
<given-names>A.V.</given-names>
</name>
<name>
<surname>Floros</surname>
<given-names>D.J.</given-names>
</name>
<name>
<surname>Da Silva</surname>
<given-names>R.R.</given-names>
</name>
<name>
<surname>Jensen</surname>
<given-names>P.R.</given-names>
</name>
<name>
<surname>Dorrestein</surname>
<given-names>P.C.</given-names>
</name>
<name>
<surname>Moore</surname>
<given-names>B.S.</given-names>
</name>
</person-group>
<article-title>Prioritizing Natural Product Diversity in a Collection of 146 Bacterial Strains Based on Growth and Extraction Protocols</article-title>
<source>J. Nat. Prod.</source>
<year>2017</year>
<volume>80</volume>
<fpage>588</fpage>
<lpage>597</lpage>
<pub-id pub-id-type="doi">10.1021/acs.jnatprod.6b00722</pub-id>
<pub-id pub-id-type="pmid">28335604</pub-id>
</element-citation>
</ref>
<ref id="B12-molecules-25-00460">
<label>12.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Corre</surname>
<given-names>C.</given-names>
</name>
<name>
<surname>Song</surname>
<given-names>L.</given-names>
</name>
<name>
<surname>O’Rourke</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Chater</surname>
<given-names>K.F.</given-names>
</name>
<name>
<surname>Challis</surname>
<given-names>G.L.</given-names>
</name>
</person-group>
<article-title>2-Alkyl-4-hydroxymethylfuran-3-carboxylic acids, Antibiotic Production Inducers Discovered by Streptomyces Coelicolor Genome Mining</article-title>
<source>Proc. Natl. Acad. Sci. USA</source>
<year>2008</year>
<volume>105</volume>
<fpage>17510</fpage>
<lpage>17515</lpage>
<pub-id pub-id-type="doi">10.1073/pnas.0805530105</pub-id>
<pub-id pub-id-type="pmid">18988741</pub-id>
</element-citation>
</ref>
<ref id="B13-molecules-25-00460">
<label>13.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Schuster</surname>
<given-names>M.</given-names>
</name>
<name>
<surname>Joseph Sexton</surname>
<given-names>D.</given-names>
</name>
<name>
<surname>Diggle</surname>
<given-names>S.P.</given-names>
</name>
<name>
<surname>Peter Greenberg</surname>
<given-names>E.</given-names>
</name>
</person-group>
<article-title>Acyl-Homoserine Lactone Quorum Sensing: From Evolution to Application</article-title>
<source>Annu. Rev. Microbiol.</source>
<year>2013</year>
<volume>67</volume>
<fpage>43</fpage>
<lpage>63</lpage>
<pub-id pub-id-type="doi">10.1146/annurev-micro-092412-155635</pub-id>
<pub-id pub-id-type="pmid">23682605</pub-id>
</element-citation>
</ref>
<ref id="B14-molecules-25-00460">
<label>14.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Sidda</surname>
<given-names>J.D.</given-names>
</name>
<name>
<surname>Poon</surname>
<given-names>V.</given-names>
</name>
<name>
<surname>Song</surname>
<given-names>L.</given-names>
</name>
<name>
<surname>Wang</surname>
<given-names>W.</given-names>
</name>
<name>
<surname>Yang</surname>
<given-names>K.</given-names>
</name>
<name>
<surname>Corre</surname>
<given-names>C.</given-names>
</name>
</person-group>
<article-title>Overproduction and Identification of Butyrolactones SCB1-8 in the Antibiotic Production Superhost: Streptomyces M1152</article-title>
<source>Org. Biomol. Chem.</source>
<year>2016</year>
<volume>14</volume>
<fpage>6390</fpage>
<lpage>6393</lpage>
<pub-id pub-id-type="doi">10.1039/C6OB00840B</pub-id>
<pub-id pub-id-type="pmid">27180870</pub-id>
</element-citation>
</ref>
<ref id="B15-molecules-25-00460">
<label>15.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Du</surname>
<given-names>Y.L.</given-names>
</name>
<name>
<surname>Shen</surname>
<given-names>X.L.</given-names>
</name>
<name>
<surname>Yu</surname>
<given-names>P.</given-names>
</name>
<name>
<surname>Bai</surname>
<given-names>L.Q.</given-names>
</name>
<name>
<surname>Li</surname>
<given-names>Y.Q.</given-names>
</name>
</person-group>
<article-title>Gamma-Butyrolactone Regulatory System of Streptomyces Chattanoogensis Links Nutrient Utilization, Metabolism, and Development</article-title>
<source>Appl. Environ. Microbiol.</source>
<year>2011</year>
<volume>77</volume>
<fpage>8415</fpage>
<lpage>8426</lpage>
<pub-id pub-id-type="doi">10.1128/AEM.05898-11</pub-id>
<pub-id pub-id-type="pmid">21948843</pub-id>
</element-citation>
</ref>
<ref id="B16-molecules-25-00460">
<label>16.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Bhasin</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Modi</surname>
<given-names>H.A.</given-names>
</name>
</person-group>
<article-title>Optimization of Fermentation Medium for the Production of Glucose Isomerase Using
<italic>Streptomyces</italic>
sp. SB-P1</article-title>
<source>Biotechnol. Res. Int.</source>
<year>2012</year>
<volume>2012</volume>
<fpage>1</fpage>
<lpage>10</lpage>
<pub-id pub-id-type="doi">10.1155/2012/874152</pub-id>
</element-citation>
</ref>
<ref id="B17-molecules-25-00460">
<label>17.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Li</surname>
<given-names>X.</given-names>
</name>
<name>
<surname>Dobretsov</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Xu</surname>
<given-names>Y.</given-names>
</name>
<name>
<surname>Xiao</surname>
<given-names>X.</given-names>
</name>
<name>
<surname>Hung</surname>
<given-names>O.</given-names>
</name>
<name>
<surname>Qian</surname>
<given-names>P.Y.</given-names>
</name>
</person-group>
<article-title>Antifouling Diketopiperazines Produced by a Deep-Sea Bacterium, Streptomyces Fungicidicus</article-title>
<source>Biofouling</source>
<year>2006</year>
<volume>22</volume>
<fpage>201</fpage>
<lpage>208</lpage>
<pub-id pub-id-type="doi">10.1080/08927010600780771</pub-id>
<pub-id pub-id-type="pmid">17290864</pub-id>
</element-citation>
</ref>
<ref id="B18-molecules-25-00460">
<label>18.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Campo</surname>
<given-names>V.L.</given-names>
</name>
<name>
<surname>Duarte</surname>
<given-names>M.C.T.</given-names>
</name>
<name>
<surname>Bastos</surname>
<given-names>J.K.</given-names>
</name>
</person-group>
<article-title>Diketopiperazines Produced by an Aspergillus Fumigatus Brazilian Strain</article-title>
<source>J. Braz. Chem. Soc.</source>
<year>2005</year>
<volume>16</volume>
<fpage>1448</fpage>
<lpage>1453</lpage>
</element-citation>
</ref>
<ref id="B19-molecules-25-00460">
<label>19.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Lee</surname>
<given-names>S.R.</given-names>
</name>
<name>
<surname>Beemelmanns</surname>
<given-names>C.</given-names>
</name>
<name>
<surname>Tsuma</surname>
<given-names>L.M.M.</given-names>
</name>
<name>
<surname>Clardy</surname>
<given-names>J.</given-names>
</name>
<name>
<surname>Cao</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Kim</surname>
<given-names>K.H.</given-names>
</name>
</person-group>
<article-title>A New Diketopiperazine, cyclo(
<sc>d</sc>
-trans-Hyp-
<sc>l</sc>
-Leu) from a Kenyan Bacterium Bacillus Licheniformis LB 8CT</article-title>
<source>Nat. Prod. Commun.</source>
<year>2016</year>
<volume>11</volume>
<fpage>461</fpage>
<lpage>463</lpage>
<pub-id pub-id-type="doi">10.1177/1934578X1601100410</pub-id>
<pub-id pub-id-type="pmid">27396193</pub-id>
</element-citation>
</ref>
<ref id="B20-molecules-25-00460">
<label>20.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Alshaibani</surname>
<given-names>M.</given-names>
</name>
<name>
<surname>Jalil</surname>
<given-names>J.</given-names>
</name>
<name>
<surname>Sidik</surname>
<given-names>N.</given-names>
</name>
<name>
<surname>Ahmad</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Kamal</surname>
<given-names>N.</given-names>
</name>
<name>
<surname>Edrada-Ebel</surname>
<given-names>R.</given-names>
</name>
<name>
<surname>MohamadZin</surname>
<given-names>N.</given-names>
</name>
</person-group>
<article-title>Isolation, Purification and Characterization of five Active Diketopiperazine Derivates from Endophytic Strptomyces SUK 25 with Antimicrobial and Cytotoxic Activities</article-title>
<source>J. Microbiol. Biotechnol.</source>
<year>2017</year>
<volume>27</volume>
<fpage>1</fpage>
<lpage>22</lpage>
<pub-id pub-id-type="pmid">27666988</pub-id>
</element-citation>
</ref>
<ref id="B21-molecules-25-00460">
<label>21.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Nishanth Kumar</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Mohandas</surname>
<given-names>C.</given-names>
</name>
<name>
<surname>Siji</surname>
<given-names>J.V.</given-names>
</name>
<name>
<surname>Rajasekharan</surname>
<given-names>K.N.</given-names>
</name>
<name>
<surname>Nambisan</surname>
<given-names>B.</given-names>
</name>
</person-group>
<article-title>Identification of Antimicrobial Compound, Diketopiperazines, from a Bacillus sp. N Strain Associated with a Rhabditid Entomopathogenic Nematode against Major Plant Pathogenic Fungi</article-title>
<source>J. Appl. Microbiol.</source>
<year>2012</year>
<volume>113</volume>
<fpage>914</fpage>
<lpage>924</lpage>
<pub-id pub-id-type="doi">10.1111/j.1365-2672.2012.05385.x</pub-id>
<pub-id pub-id-type="pmid">22747978</pub-id>
</element-citation>
</ref>
<ref id="B22-molecules-25-00460">
<label>22.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Maglangit</surname>
<given-names>F.</given-names>
</name>
<name>
<surname>Tong</surname>
<given-names>M.H.</given-names>
</name>
<name>
<surname>Jaspars</surname>
<given-names>M.</given-names>
</name>
<name>
<surname>Kyeremeh</surname>
<given-names>K.</given-names>
</name>
<name>
<surname>Deng</surname>
<given-names>H.</given-names>
</name>
</person-group>
<article-title>Legonoxamines A-B, Two New Hydroxamate Siderophores from the Soil Bacterium,
<italic>Streptomyces</italic>
sp. MA37</article-title>
<source>Tetrahedron Lett.</source>
<year>2019</year>
<volume>60</volume>
<fpage>75</fpage>
<lpage>79</lpage>
<pub-id pub-id-type="doi">10.1016/j.tetlet.2018.11.063</pub-id>
</element-citation>
</ref>
<ref id="B23-molecules-25-00460">
<label>23.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Yamanaka</surname>
<given-names>K.</given-names>
</name>
<name>
<surname>Oikawa</surname>
<given-names>H.</given-names>
</name>
<name>
<surname>Ogawa</surname>
<given-names>H.O.</given-names>
</name>
<name>
<surname>Hosono</surname>
<given-names>K.</given-names>
</name>
<name>
<surname>Shinmachi</surname>
<given-names>F.</given-names>
</name>
<name>
<surname>Takano</surname>
<given-names>H.</given-names>
</name>
<name>
<surname>Sakuda</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Beppu</surname>
<given-names>T.</given-names>
</name>
<name>
<surname>Ueda</surname>
<given-names>K.</given-names>
</name>
</person-group>
<article-title>Desferrioxamine E Produced by Streptomyces Griseus Stimulates Growth and Development of Streptomyces Tanashiensis</article-title>
<source>Microbiology</source>
<year>2005</year>
<volume>151</volume>
<fpage>2899</fpage>
<lpage>2905</lpage>
<pub-id pub-id-type="doi">10.1099/mic.0.28139-0</pub-id>
<pub-id pub-id-type="pmid">16151202</pub-id>
</element-citation>
</ref>
<ref id="B24-molecules-25-00460">
<label>24.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Meiwes</surname>
<given-names>J.</given-names>
</name>
<name>
<surname>Fiedler</surname>
<given-names>H.P.</given-names>
</name>
<name>
<surname>Zähner</surname>
<given-names>H.</given-names>
</name>
<name>
<surname>Konetschny-Rapp</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Jung</surname>
<given-names>G.</given-names>
</name>
</person-group>
<article-title>Production of Desferrioxamine E and New Analogues by Directed Fermentation and Feeding Fermentation</article-title>
<source>Appl. Microbiol. Biotechnol.</source>
<year>1990</year>
<volume>32</volume>
<fpage>505</fpage>
<lpage>510</lpage>
<pub-id pub-id-type="doi">10.1007/BF00173718</pub-id>
<pub-id pub-id-type="pmid">1367428</pub-id>
</element-citation>
</ref>
<ref id="B25-molecules-25-00460">
<label>25.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Corre</surname>
<given-names>C.</given-names>
</name>
<name>
<surname>Haynes</surname>
<given-names>S.W.</given-names>
</name>
<name>
<surname>Malet</surname>
<given-names>N.</given-names>
</name>
<name>
<surname>Song</surname>
<given-names>L.</given-names>
</name>
<name>
<surname>Challis</surname>
<given-names>G.L.</given-names>
</name>
</person-group>
<article-title>A Butenolide Intermediate in Methylenomycin Furan Biosynthesis is Implied by Incorporation of Stereospecifically 13C-Labelled Glycerols</article-title>
<source>Chem. Commun.</source>
<year>2010</year>
<volume>46</volume>
<fpage>4079</fpage>
<lpage>4081</lpage>
<pub-id pub-id-type="doi">10.1039/c000496k</pub-id>
<pub-id pub-id-type="pmid">20358097</pub-id>
</element-citation>
</ref>
<ref id="B26-molecules-25-00460">
<label>26.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Weber</surname>
<given-names>T.</given-names>
</name>
<name>
<surname>Blin</surname>
<given-names>K.</given-names>
</name>
<name>
<surname>Duddela</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Krug</surname>
<given-names>D.</given-names>
</name>
<name>
<surname>Kim</surname>
<given-names>H.U.</given-names>
</name>
<name>
<surname>Bruccoleri</surname>
<given-names>R.</given-names>
</name>
<name>
<surname>Lee</surname>
<given-names>S.Y.</given-names>
</name>
<name>
<surname>Fischbach</surname>
<given-names>M.A.</given-names>
</name>
<name>
<surname>Müller</surname>
<given-names>R.</given-names>
</name>
<name>
<surname>Wohlleben</surname>
<given-names>W.</given-names>
</name>
<etal></etal>
</person-group>
<article-title>AntiSMASH 3.0-A Comprehensive Resource for the Genome Mining of Biosynthetic Gene Clusters</article-title>
<source>Nucleic Acids Res.</source>
<year>2015</year>
<volume>43</volume>
<fpage>W237</fpage>
<lpage>W243</lpage>
<pub-id pub-id-type="doi">10.1093/nar/gkv437</pub-id>
<pub-id pub-id-type="pmid">25948579</pub-id>
</element-citation>
</ref>
<ref id="B27-molecules-25-00460">
<label>27.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Sayers</surname>
<given-names>E.W.</given-names>
</name>
<name>
<surname>Agarwala</surname>
<given-names>R.</given-names>
</name>
<name>
<surname>Bolton</surname>
<given-names>E.E.</given-names>
</name>
<name>
<surname>Brister</surname>
<given-names>J.R.</given-names>
</name>
<name>
<surname>Canese</surname>
<given-names>K.</given-names>
</name>
<name>
<surname>Clark</surname>
<given-names>K.</given-names>
</name>
<name>
<surname>Connor</surname>
<given-names>R.</given-names>
</name>
<name>
<surname>Fiorini</surname>
<given-names>N.</given-names>
</name>
<name>
<surname>Funk</surname>
<given-names>K.</given-names>
</name>
<name>
<surname>Hefferon</surname>
<given-names>T.</given-names>
</name>
<etal></etal>
</person-group>
<article-title>Database Resources of the National Center for Biotechnology Information</article-title>
<source>Nucleic Acids Res.</source>
<year>2019</year>
<volume>47</volume>
<fpage>D23</fpage>
<lpage>D28</lpage>
<pub-id pub-id-type="doi">10.1093/nar/gky1069</pub-id>
<pub-id pub-id-type="pmid">30395293</pub-id>
</element-citation>
</ref>
<ref id="B28-molecules-25-00460">
<label>28.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Zallot</surname>
<given-names>R.</given-names>
</name>
<name>
<surname>Oberg</surname>
<given-names>N.O.</given-names>
</name>
<name>
<surname>Gerlt</surname>
<given-names>J.A.</given-names>
</name>
</person-group>
<article-title>‘Democratized’ Genomic Enzymology Web Tools for Functional Assignment</article-title>
<source>Curr. Opin. Chem. Biol.</source>
<year>2018</year>
<volume>47</volume>
<fpage>77</fpage>
<lpage>85</lpage>
<pub-id pub-id-type="doi">10.1016/j.cbpa.2018.09.009</pub-id>
<pub-id pub-id-type="pmid">30268904</pub-id>
</element-citation>
</ref>
<ref id="B29-molecules-25-00460">
<label>29.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Horinouchi</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Beppu</surname>
<given-names>T.</given-names>
</name>
</person-group>
<article-title>A-factor and Streptomycin Biosynthesis in Streptomyces Griseus</article-title>
<source>Antonie Van Leeuwenhoek</source>
<year>1993</year>
<volume>64</volume>
<fpage>177</fpage>
<lpage>186</lpage>
<pub-id pub-id-type="doi">10.1007/BF00873026</pub-id>
<pub-id pub-id-type="pmid">8092858</pub-id>
</element-citation>
</ref>
<ref id="B30-molecules-25-00460">
<label>30.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Davis</surname>
<given-names>J.B.</given-names>
</name>
<name>
<surname>Bailey</surname>
<given-names>J.D.</given-names>
</name>
<name>
<surname>Sello</surname>
<given-names>J.K.</given-names>
</name>
</person-group>
<article-title>Biomimetic Synthesis of a New Class of Bacterial Signaling Molecules</article-title>
<source>Org. Lett.</source>
<year>2009</year>
<volume>11</volume>
<fpage>2984</fpage>
<lpage>2987</lpage>
<pub-id pub-id-type="doi">10.1021/ol9009893</pub-id>
<pub-id pub-id-type="pmid">19545145</pub-id>
</element-citation>
</ref>
<ref id="B31-molecules-25-00460">
<label>31.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Alberti</surname>
<given-names>F.</given-names>
</name>
<name>
<surname>Leng</surname>
<given-names>D.J.</given-names>
</name>
<name>
<surname>Wilkening</surname>
<given-names>I.</given-names>
</name>
<name>
<surname>Song</surname>
<given-names>L.</given-names>
</name>
<name>
<surname>Tosin</surname>
<given-names>M.</given-names>
</name>
<name>
<surname>Corre</surname>
<given-names>C.</given-names>
</name>
</person-group>
<article-title>Triggering the Expression of a Silent Gene Cluster from Genetically Intractable Bacteria Results in Scleric Acid Discovery</article-title>
<source>Chem. Sci.</source>
<year>2019</year>
<volume>10</volume>
<fpage>453</fpage>
<lpage>463</lpage>
<pub-id pub-id-type="doi">10.1039/C8SC03814G</pub-id>
<pub-id pub-id-type="pmid">30746093</pub-id>
</element-citation>
</ref>
<ref id="B32-molecules-25-00460">
<label>32.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Gordeuk</surname>
<given-names>V.R.</given-names>
</name>
<name>
<surname>Thuma</surname>
<given-names>P.E.</given-names>
</name>
<name>
<surname>Brittenbam</surname>
<given-names>G.M.</given-names>
</name>
</person-group>
<article-title>Iron Chelation Therapy for Malaria</article-title>
<source>Adv. Exp. Med. Biol.</source>
<year>1994</year>
<volume>356</volume>
<fpage>371</fpage>
<lpage>383</lpage>
<pub-id pub-id-type="pmid">7887243</pub-id>
</element-citation>
</ref>
<ref id="B33-molecules-25-00460">
<label>33.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Rotheneder</surname>
<given-names>A.</given-names>
</name>
<name>
<surname>Fritsche</surname>
<given-names>G.</given-names>
</name>
<name>
<surname>Heinisch</surname>
<given-names>L.</given-names>
</name>
<name>
<surname>Heggemann</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Larcher</surname>
<given-names>C.</given-names>
</name>
<name>
<surname>Möllmann</surname>
<given-names>U.</given-names>
</name>
<name>
<surname>Weiss</surname>
<given-names>G.</given-names>
</name>
</person-group>
<article-title>Effects of Synthetic Siderophores on Proliferation of Plasmodium falciparum in Infected Human Erythrocytes</article-title>
<source>Antimicrob. Agents Chemother.</source>
<year>2013</year>
<volume>46</volume>
<fpage>9</fpage>
<lpage>13</lpage>
</element-citation>
</ref>
<ref id="B34-molecules-25-00460">
<label>34.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Ferrer</surname>
<given-names>P.</given-names>
</name>
<name>
<surname>Tripathi</surname>
<given-names>A.K.</given-names>
</name>
<name>
<surname>Clark</surname>
<given-names>M.A.</given-names>
</name>
<name>
<surname>Hand</surname>
<given-names>C.C.</given-names>
</name>
<name>
<surname>Rienhoff</surname>
<given-names>H.Y.</given-names>
</name>
<name>
<surname>Sullivan</surname>
<given-names>D.J.</given-names>
</name>
</person-group>
<article-title>Antimalarial Iron Chelator, FBS0701, Shows Asexual and Gametocyte Plasmodium Falciparum Activity and Single Oral Dose Cure in a Murine Malaria Model</article-title>
<source>PLoS ONE</source>
<year>2012</year>
<volume>7</volume>
<fpage>1</fpage>
<lpage>7</lpage>
<pub-id pub-id-type="doi">10.1371/journal.pone.0037171</pub-id>
</element-citation>
</ref>
<ref id="B35-molecules-25-00460">
<label>35.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Pradines</surname>
<given-names>B.</given-names>
</name>
<name>
<surname>Rolain</surname>
<given-names>J.M.</given-names>
</name>
<name>
<surname>Ramiandrasoa</surname>
<given-names>F.</given-names>
</name>
<name>
<surname>Fusai</surname>
<given-names>T.</given-names>
</name>
<name>
<surname>Mosnier</surname>
<given-names>J.</given-names>
</name>
<name>
<surname>Rogier</surname>
<given-names>C.</given-names>
</name>
<name>
<surname>Daries</surname>
<given-names>W.</given-names>
</name>
<name>
<surname>Baret</surname>
<given-names>E.</given-names>
</name>
<name>
<surname>Kunesch</surname>
<given-names>G.</given-names>
</name>
<name>
<surname>Le Bras</surname>
<given-names>J.</given-names>
</name>
<etal></etal>
</person-group>
<article-title>Iron Chelators as Antimalarial Agents: In Vitro Activity of Dicatecholate against
<italic>Plasmodium falciparum</italic>
</article-title>
<source>J. Antimicrob. Chemother.</source>
<year>2002</year>
<volume>50</volume>
<fpage>177</fpage>
<lpage>187</lpage>
<pub-id pub-id-type="doi">10.1093/jac/dkf104</pub-id>
<pub-id pub-id-type="pmid">12161397</pub-id>
</element-citation>
</ref>
<ref id="B36-molecules-25-00460">
<label>36.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Pérez-Moreno</surname>
<given-names>G.</given-names>
</name>
<name>
<surname>Cantizani</surname>
<given-names>J.</given-names>
</name>
<name>
<surname>Sánchez-Carrasco</surname>
<given-names>P.</given-names>
</name>
<name>
<surname>Ruiz-Pérez</surname>
<given-names>L.M.</given-names>
</name>
<name>
<surname>Martín</surname>
<given-names>J.</given-names>
</name>
<name>
<surname>El Aouad</surname>
<given-names>N.</given-names>
</name>
<name>
<surname>Pérez-Victoria</surname>
<given-names>I.</given-names>
</name>
<name>
<surname>Tormo</surname>
<given-names>J.R.</given-names>
</name>
<name>
<surname>González-Menendez</surname>
<given-names>V.</given-names>
</name>
<name>
<surname>González</surname>
<given-names>I.</given-names>
</name>
<etal></etal>
</person-group>
<article-title>Discovery of new Compounds Active against Plasmodium Falciparum by High Throughput Screening of Microbial Natural Products</article-title>
<source>PLoS ONE</source>
<year>2016</year>
<volume>11</volume>
<fpage>1</fpage>
<lpage>16</lpage>
<pub-id pub-id-type="doi">10.1371/journal.pone.0145812</pub-id>
</element-citation>
</ref>
<ref id="B37-molecules-25-00460">
<label>37.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Pluskal</surname>
<given-names>T.</given-names>
</name>
<name>
<surname>Castillo</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Villar-Briones</surname>
<given-names>A.</given-names>
</name>
<name>
<surname>Orešič</surname>
<given-names>M.</given-names>
</name>
</person-group>
<article-title>MZmine 2: Modular Framework for Processing, Visualizing, and Analyzing Mass Spectrometry-based Molecular Profile Data</article-title>
<source>BMC Bioinformatics</source>
<year>2010</year>
<volume>11</volume>
<elocation-id>395</elocation-id>
<pub-id pub-id-type="doi">10.1186/1471-2105-11-395</pub-id>
<pub-id pub-id-type="pmid">20650010</pub-id>
</element-citation>
</ref>
<ref id="B38-molecules-25-00460">
<label>38.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Pylayeva-Gupta</surname>
<given-names>Y.</given-names>
</name>
</person-group>
<article-title>The Spectral Networks Paradigm in High Throughput Mass Spectrometry</article-title>
<source>Bone</source>
<year>2011</year>
<volume>23</volume>
<fpage>1</fpage>
<lpage>7</lpage>
</element-citation>
</ref>
<ref id="B39-molecules-25-00460">
<label>39.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Shannon</surname>
<given-names>P.</given-names>
</name>
<name>
<surname>Markiel</surname>
<given-names>A.</given-names>
</name>
<name>
<surname>Ozier</surname>
<given-names>O.</given-names>
</name>
<name>
<surname>Baliga</surname>
<given-names>N.S.</given-names>
</name>
<name>
<surname>Wang</surname>
<given-names>J.T.</given-names>
</name>
<name>
<surname>Ramage</surname>
<given-names>D.</given-names>
</name>
<name>
<surname>Amin</surname>
<given-names>N.</given-names>
</name>
<name>
<surname>Schwikowski</surname>
<given-names>B.</given-names>
</name>
<name>
<surname>Ideker</surname>
<given-names>T.</given-names>
</name>
</person-group>
<article-title>Cytoscape: A Software Environment for Integrated Models of Biomolecular Interaction Networks</article-title>
<source>Genome Res.</source>
<year>2003</year>
<fpage>2498</fpage>
<lpage>2504</lpage>
<pub-id pub-id-type="doi">10.1101/gr.1239303</pub-id>
<pub-id pub-id-type="pmid">14597658</pub-id>
</element-citation>
</ref>
<ref id="B40-molecules-25-00460">
<label>40.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Aziz</surname>
<given-names>R.K.</given-names>
</name>
<name>
<surname>Bartels</surname>
<given-names>D.</given-names>
</name>
<name>
<surname>Best</surname>
<given-names>A.A.</given-names>
</name>
<name>
<surname>DeJongh</surname>
<given-names>M.</given-names>
</name>
<name>
<surname>Disz</surname>
<given-names>T.</given-names>
</name>
<name>
<surname>Edwards</surname>
<given-names>R.A.</given-names>
</name>
<name>
<surname>Formsma</surname>
<given-names>K.</given-names>
</name>
<name>
<surname>Gerdes</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Glass</surname>
<given-names>E.M.</given-names>
</name>
<name>
<surname>Kubal</surname>
<given-names>M.</given-names>
</name>
<etal></etal>
</person-group>
<article-title>The RAST Server: Rapid Annotations Using Subsystems Technology</article-title>
<source>BMC Genomics</source>
<year>2008</year>
<volume>9</volume>
<elocation-id>75</elocation-id>
<pub-id pub-id-type="doi">10.1186/1471-2164-9-75</pub-id>
<pub-id pub-id-type="pmid">18261238</pub-id>
</element-citation>
</ref>
<ref id="B41-molecules-25-00460">
<label>41.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Saitou</surname>
<given-names>N.</given-names>
</name>
<name>
<surname>Nei</surname>
<given-names>M.</given-names>
</name>
</person-group>
<article-title>The Neighbor-Joining Method: A New Method for Reconstructing Phylogenetic Trees</article-title>
<source>Mol. Biol. Evol.</source>
<year>1987</year>
<volume>4</volume>
<fpage>406</fpage>
<lpage>425</lpage>
<pub-id pub-id-type="pmid">3447015</pub-id>
</element-citation>
</ref>
<ref id="B42-molecules-25-00460">
<label>42.</label>
<element-citation publication-type="journal">
<person-group person-group-type="author">
<name>
<surname>Kumar</surname>
<given-names>S.</given-names>
</name>
<name>
<surname>Stecher</surname>
<given-names>G.</given-names>
</name>
<name>
<surname>Tamura</surname>
<given-names>K.</given-names>
</name>
</person-group>
<article-title>MEGA7: Molecular Evolutionary Genetics Analysis Version 7.0 for Bigger Datasets</article-title>
<source>Mol. Biol. Evol.</source>
<year>2016</year>
<volume>33</volume>
<fpage>1870</fpage>
<lpage>1874</lpage>
<pub-id pub-id-type="doi">10.1093/molbev/msw054</pub-id>
<pub-id pub-id-type="pmid">27004904</pub-id>
</element-citation>
</ref>
<ref id="B43-molecules-25-00460">
<label>43.</label>
<element-citation publication-type="book">
<person-group person-group-type="author">
<name>
<surname>Carpenter</surname>
<given-names>D.E.</given-names>
</name>
<name>
<surname>Karen Anderson Diane Citron</surname>
<given-names>C.M.</given-names>
</name>
<name>
<surname>JoAnn Dzink-Fox</surname>
<given-names>B.L.</given-names>
</name>
<name>
<surname>Meredith Hackel</surname>
<given-names>M.</given-names>
</name>
<name>
<surname>Jenkins</surname>
<given-names>S.G.</given-names>
</name>
<name>
<surname>Cindy Knapp</surname>
<given-names>F.</given-names>
</name>
<name>
<surname>Laura Koeth</surname>
<given-names>M.</given-names>
</name>
<name>
<surname>Audrey Schuetz</surname>
<given-names>M.N.</given-names>
</name>
<name>
<surname>Hannah Wexler</surname>
<given-names>D.</given-names>
</name>
</person-group>
<source>Methods for Antimicrobial Susceptibility Testing of Anaerobic Bacteria</source>
<edition>9th ed.</edition>
<comment>CLSI standard M11</comment>
<publisher-name>Clinical and Laboratory Standards Institute</publisher-name>
<publisher-loc>Wayne, PA, USA</publisher-loc>
<year>2018</year>
<fpage>11</fpage>
<lpage>19</lpage>
</element-citation>
</ref>
</ref-list>
<sec sec-type="display-objects">
<title>Figures, Scheme and Tables</title>
<fig id="molecules-25-00460-f001" orientation="portrait" position="float">
<label>Figure 1</label>
<caption>
<p>Isolated metabolites from
<italic>Streptomyces</italic>
sp. RK44. structures of which were elucidated by NMR. Structure of AHFA
<bold>1</bold>
with COSY (
<bold>―</bold>
) and key HMBC (
<bold>→</bold>
) correlations.</p>
</caption>
<graphic xlink:href="molecules-25-00460-g001"></graphic>
</fig>
<fig id="molecules-25-00460-f002" orientation="portrait" position="float">
<label>Figure 2</label>
<caption>
<p>Comparison of the
<italic>ahfa</italic>
BGC in
<italic>Streptomyces</italic>
sp. RK44 with the
<italic>mmf</italic>
gene cluster on the SCP1 plasmid of
<italic>S. coelicolor</italic>
A3(2). Homologous genes are colored the same, and sequence identities between each of the encoded proteins are indicated in
<xref rid="molecules-25-00460-t002" ref-type="table">Table 2</xref>
.</p>
</caption>
<graphic xlink:href="molecules-25-00460-g002"></graphic>
</fig>
<fig id="molecules-25-00460-sch001" orientation="portrait" position="float">
<object-id pub-id-type="pii">molecules-25-00460-sch001_Scheme 1</object-id>
<label>Scheme 1</label>
<caption>
<p>Proposed biosynthesis pathway of
<bold>1</bold>
.</p>
</caption>
<graphic xlink:href="molecules-25-00460-sch001"></graphic>
</fig>
<fig id="molecules-25-00460-f003" orientation="portrait" position="float">
<label>Figure 3</label>
<caption>
<p>(
<bold>A</bold>
) A2058 cell treated with 50µg/mL staurosporine (
<bold>B</bold>
) A2058 cell treated with 50µg/mL AHFA 1 (
<bold>C</bold>
) A2058 cell treated with culture media. Cell viability was quantified by Aqueous One Solution Reagent by a colourimetric method for determining the number of viable cells in proliferation or cytotoxicity assays. A2058 cells were left untreated or were treated with AHFA
<bold>1</bold>
for 72 h and morphological changes of the cells were observed by light microscope (Scale bar 26 μm).</p>
</caption>
<graphic xlink:href="molecules-25-00460-g003"></graphic>
</fig>
<fig id="molecules-25-00460-f004" orientation="portrait" position="float">
<label>Figure 4</label>
<caption>
<p>Phylogenetic analysis of 16S rDNA sequences of
<italic>Streptomyces</italic>
sp. RK44 and other known
<italic>Streptomyces</italic>
species, indicating that
<italic>Streptomyces</italic>
sp. RK44 is a new
<italic>Streptomyces</italic>
species.</p>
</caption>
<graphic xlink:href="molecules-25-00460-g004"></graphic>
</fig>
<table-wrap id="molecules-25-00460-t001" orientation="portrait" position="float">
<object-id pub-id-type="pii">molecules-25-00460-t001_Table 1</object-id>
<label>Table 1</label>
<caption>
<p>NMR data of AHFA
<bold>1</bold>
in CD
<sub>3</sub>
OD and DMSO-
<italic>d</italic>
<sub>6</sub>
at 600 MHz and 298 K.</p>
</caption>
<table frame="hsides" rules="groups">
<thead>
<tr>
<th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1"></th>
<th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1"></th>
<th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">CD
<sub>3</sub>
OD</th>
<th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1"></th>
<th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">DMSO-
<italic>d</italic>
<sub>6</sub>
</th>
</tr>
<tr>
<th align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">POSITION</th>
<th align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">
<sup>13</sup>
C (ppm)</th>
<th align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">
<sup>1</sup>
H (Integral, Mult.)</th>
<th align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">
<sup>13</sup>
C (ppm)</th>
<th align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">
<sup>1</sup>
H (Integral, Mult.)</th>
</tr>
</thead>
<tbody>
<tr>
<td align="center" valign="middle" rowspan="1" colspan="1">4′</td>
<td align="center" valign="middle" rowspan="1" colspan="1">12.7</td>
<td align="center" valign="middle" rowspan="1" colspan="1">0.92 (3H, t)</td>
<td align="center" valign="middle" rowspan="1" colspan="1">13.9</td>
<td align="center" valign="middle" rowspan="1" colspan="1">1.01 (3H, t)</td>
</tr>
<tr>
<td align="center" valign="middle" rowspan="1" colspan="1">3′</td>
<td align="center" valign="middle" rowspan="1" colspan="1">21.9</td>
<td align="center" valign="middle" rowspan="1" colspan="1">1.35 (2H, hep)</td>
<td align="center" valign="middle" rowspan="1" colspan="1">21.9</td>
<td align="center" valign="middle" rowspan="1" colspan="1">1.41 (2H, hep)</td>
</tr>
<tr>
<td align="center" valign="middle" rowspan="1" colspan="1">2′</td>
<td align="center" valign="middle" rowspan="1" colspan="1">29.8</td>
<td align="center" valign="middle" rowspan="1" colspan="1">1.63 (2H, pent)</td>
<td align="center" valign="middle" rowspan="1" colspan="1">29.9</td>
<td align="center" valign="middle" rowspan="1" colspan="1">1.68 (2H, pent)</td>
</tr>
<tr>
<td align="center" valign="middle" rowspan="1" colspan="1">1′</td>
<td align="center" valign="middle" rowspan="1" colspan="1">26.6</td>
<td align="center" valign="middle" rowspan="1" colspan="1">2.95 (2H, t)</td>
<td align="center" valign="middle" rowspan="1" colspan="1">26.4</td>
<td align="center" valign="middle" rowspan="1" colspan="1">3.03 (2H, t)</td>
</tr>
<tr>
<td align="center" valign="middle" rowspan="1" colspan="1">2</td>
<td align="center" valign="middle" rowspan="1" colspan="1">162.1</td>
<td align="center" valign="middle" rowspan="1" colspan="1">-</td>
<td align="center" valign="middle" rowspan="1" colspan="1">161.3 </td>
<td align="center" valign="middle" rowspan="1" colspan="1">-</td>
</tr>
<tr>
<td align="center" valign="middle" rowspan="1" colspan="1">7</td>
<td align="center" valign="middle" rowspan="1" colspan="1">54.1</td>
<td align="center" valign="middle" rowspan="1" colspan="1">4.52 (2H, s)</td>
<td align="center" valign="middle" rowspan="1" colspan="1">54.1</td>
<td align="center" valign="middle" rowspan="1" colspan="1">4.53 (2H, s)</td>
</tr>
<tr>
<td align="center" valign="middle" rowspan="1" colspan="1">6</td>
<td align="center" valign="middle" rowspan="1" colspan="1">171.6</td>
<td align="center" valign="middle" rowspan="1" colspan="1">-</td>
<td align="center" valign="middle" rowspan="1" colspan="1">169.9</td>
<td align="center" valign="middle" rowspan="1" colspan="1">-</td>
</tr>
<tr>
<td align="center" valign="middle" rowspan="1" colspan="1">5</td>
<td align="center" valign="middle" rowspan="1" colspan="1">139.1</td>
<td align="center" valign="middle" rowspan="1" colspan="1">7.38 (1H, s)</td>
<td align="center" valign="middle" rowspan="1" colspan="1">138.9</td>
<td align="center" valign="middle" rowspan="1" colspan="1">7.64 (1H, s)</td>
</tr>
<tr>
<td align="center" valign="middle" rowspan="1" colspan="1">4</td>
<td align="center" valign="middle" rowspan="1" colspan="1">123.1</td>
<td align="center" valign="middle" rowspan="1" colspan="1">-</td>
<td align="center" valign="middle" rowspan="1" colspan="1">124.2</td>
<td align="center" valign="middle" rowspan="1" colspan="1">-</td>
</tr>
<tr>
<td align="center" valign="middle" rowspan="1" colspan="1">3</td>
<td align="center" valign="middle" rowspan="1" colspan="1">115.8</td>
<td align="center" valign="middle" rowspan="1" colspan="1">-</td>
<td align="center" valign="middle" rowspan="1" colspan="1">117.0</td>
<td align="center" valign="middle" rowspan="1" colspan="1">-</td>
</tr>
<tr>
<td align="center" valign="middle" rowspan="1" colspan="1">NH
<sub>2</sub>
</td>
<td align="center" valign="middle" rowspan="1" colspan="1">-</td>
<td align="center" valign="middle" rowspan="1" colspan="1">-</td>
<td align="center" valign="middle" rowspan="1" colspan="1">-</td>
<td align="center" valign="middle" rowspan="1" colspan="1">6.53 (2H, br)</td>
</tr>
<tr>
<td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">OH</td>
<td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td>
<td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td>
<td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td>
<td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">4.05 (1H, br)</td>
</tr>
</tbody>
</table>
</table-wrap>
<table-wrap id="molecules-25-00460-t002" orientation="portrait" position="float">
<object-id pub-id-type="pii">molecules-25-00460-t002_Table 2</object-id>
<label>Table 2</label>
<caption>
<p>Deduced functions of open reading frames (ORFs) in
<italic>ahfa</italic>
biosynthetic gene cluster.</p>
</caption>
<table frame="hsides" rules="groups">
<thead>
<tr>
<th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Protein</th>
<th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">AA</th>
<th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Homologue
<break></break>
(% Identity/% Similarity)</th>
<th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Predicted Encoded Function</th>
</tr>
</thead>
<tbody>
<tr>
<td align="center" valign="middle" rowspan="1" colspan="1">AhfaR</td>
<td align="center" valign="middle" rowspan="1" colspan="1">210</td>
<td align="center" valign="middle" rowspan="1" colspan="1">MmyR (62/75)
<italic>S. coelicolor</italic>
A3(2)
<break></break>
A factor receptor (30/48)
<italic>S. griseus</italic>
</td>
<td align="center" valign="middle" rowspan="1" colspan="1">TetR/AcR family transcriptional regulator</td>
</tr>
<tr>
<td align="center" valign="middle" rowspan="1" colspan="1">AhfaP</td>
<td align="center" valign="middle" rowspan="1" colspan="1">243</td>
<td align="center" valign="middle" rowspan="1" colspan="1">MmfP (46/58)
<italic>S. coelicolor</italic>
A3(2)</td>
<td align="center" valign="middle" rowspan="1" colspan="1">Phosphatase/Hydrolase</td>
</tr>
<tr>
<td align="center" valign="middle" rowspan="1" colspan="1">AhfaH</td>
<td align="center" valign="middle" rowspan="1" colspan="1">384</td>
<td align="center" valign="middle" rowspan="1" colspan="1">MmfH (58/66)
<italic>S. coelicolor</italic>
A3(2)</td>
<td align="center" valign="middle" rowspan="1" colspan="1">Oxidoreductase</td>
</tr>
<tr>
<td align="center" valign="middle" rowspan="1" colspan="1">AhfaL</td>
<td align="center" valign="middle" rowspan="1" colspan="1">334</td>
<td align="center" valign="middle" rowspan="1" colspan="1">MmfL (42/53)
<italic>S. coelicolor</italic>
A3(2)
<break></break>
AfsA (32/42)
<italic>S. griseus</italic>
</td>
<td align="center" valign="middle" rowspan="1" colspan="1">Butenolide synthase/
<break></break>
A factor biosynthesis</td>
</tr>
<tr>
<td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">AhfaS</td>
<td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">216</td>
<td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">MmfR (46/62)
<italic>S. coelicolor</italic>
A3(2)</td>
<td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">TetR/AcR family transcriptional regulator</td>
</tr>
</tbody>
</table>
</table-wrap>
</sec>
</back>
</pmc>
</record>

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