Secondary metabolites of mangrove Streptomyces sp. Tra 9875-2

Abstract

In the course of our investigation for bioactive metabolites of the actinomycetes, the strain TRA 9875-2 was isolated from a rotten bark sample collected from a mangrove forest along the Andaman coast, Trang province. Based on morphological, cultural, physiological, biochemical, and cell wall component studies, the strain TRA 9875-2 was identified as Streptomyces. The ethyl acetate extract from fermentation broth of this strain significantly inhibited the growth of Candida albicans ATCC 10231 and Staphylococcus aureus ATCC 25923. Antimicrobial assay-guided fractionation of the ethyl acetate extract yielded two known ansamycins, geldanamycin and 17-Odemethylgeldanamycin along with a new compound, 17-Odemethyldihydrogeldanamycin. The chemical structures of the isolated compounds were elucidated through extensive analyses of their UY, IR, MS, and NMR spectroscopic data and comparison with literatures. Geldanamycin exhibited significant antifungal activity against c. albicans ATCC 10231, cytotoxic activity against human epidermoid and breast cancer cell lines, and antimalarial activity against Plasmodium falciparum (Kl, multidrugs resistant strain), while 17-O-demethylgeldanamycin exhibited weak cytotoxic activity against human epidermoid and breast cancer cell lines.