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Antibacterial Polyketides from the Marine Alga-Derived Endophitic Streptomyces sundarbansensis: A Study on Hydroxypyrone Tautomerism
Laboratory of Applied Microbiology, Faculty of Nature Science and Life, University of Bejaia, Targa Ouzemmour 06000, Algeria
Bioorganic Chemistry Laboratory, Department of Physics, University of Trento, via Sommarive 14, I-38123 Povo-Trento, Italy
* Author to whom correspondence should be addressed.
Received: 14 November 2012; in revised form: 4 December 2012 / Accepted: 25 December 2012 / Published: 10 January 2013
Abstract: Polyketide 13 [=2-hydroxy-5-((6-hydroxy-4-oxo-4H-pyran-2-yl)methyl)-2- propylchroman-4-one] and three related known compounds 7, 9 and 11 were obtained and structurally characterized from Streptomyces sundarbansensis strain, an endophytic actinomycete isolated from the Algerian marine brown algae Fucus sp. Compound 13 was obtained as the major metabolite from optimized culture conditions, by using Agar state fermentation. Due to tautomeric equilibrium, 13 in CD3OD solution was able to incorporate five deuterium atoms, as deduced by NMR and ESI-MS/MS analysis. The 2-hydroxy-γ-pyrone form was established for these metabolites based on the comparison of their experimental IR spectra with the DFT calculated ones, for both the corresponding 4-hydroxy-α-pyrone and 2-hydroxy-γ-pyrone forms. During antibacterial evaluation, compound 13 stood out as the most active of the series, showing a selective activity against the gram positive pathogenic methicillin-resistant S. aureus (MRSA, MIC = 6 μΜ), with a bacteriostatic effect.
Keywords: marine Streptomyces; antibacterial activity; phaeochromycins; density functional calculations; hydroxypyrone tautomerism
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Djinni, I.; Defant, A.; Kecha, M.; Mancini, I. Antibacterial Polyketides from the Marine Alga-Derived Endophitic Streptomyces sundarbansensis: A Study on Hydroxypyrone Tautomerism. Mar. Drugs 2013, 11, 124-135.
Djinni I, Defant A, Kecha M, Mancini I. Antibacterial Polyketides from the Marine Alga-Derived Endophitic Streptomyces sundarbansensis: A Study on Hydroxypyrone Tautomerism. Marine Drugs. 2013; 11(1):124-135.
Djinni, Ibtissem; Defant, Andrea; Kecha, Mouloud; Mancini, Ines. 2013. "Antibacterial Polyketides from the Marine Alga-Derived Endophitic Streptomyces sundarbansensis: A Study on Hydroxypyrone Tautomerism." Mar. Drugs 11, no. 1: 124-135.