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Screening of terrestrial Streptomyces leading to identification of new stereoisomeric anthracyclines

Abdelfattah, Mohamed S.
World journal of microbiology & biotechnology 2008 v.24 no.11 pp. 2619-2625
Streptomyces, agar, anthracyclines, biosynthesis, breast neoplasms, humans, lung neoplasms, metabolites, mice, nuclear magnetic resonance spectroscopy, oatmeal, pH, screening, soil sampling, stereochemistry, Egypt
Thirty different Streptomyces strains were isolated from soil samples collected from different places in Egypt. The strains were isolated using Oatmeal agar and ISP medium 2 agar at pH 7.5. The isolate Streptomyces sp. Eg23 was selected for further working up to yield three new streoisomers of anthracycline metabolites. The structures were elucidated as (7R, 9R, 10S)-e-Rhodomycinone (1), (7R, 9R, 10S) Aklavinone (2), and (9R, 10S) 7-Desoxy-z-Rhodomycinone (3) by interpretation of their 1D and 2D NMR spectra. The absolute stereochemistry of 1 was confirmed by modified Mosher's method. The (7R, 9R, 10S)-e-Rhodomycinone (1) showed activity against human lung cancer cell H460, murine Lewis lung cancer cell LL/2 and human breast cancer cell MCF-7. Compounds 1-3 were known synthetically, but until now have not been isolated as natural products from a microorganism. The results showed that the Streptomyces sp. Eg23 seems to be an interesting target for studying the regio-and stereochemistry of the cyclization step catalysed by polyketide cyclases to produce new anthracyclines through combinatorial biosynthesis.