Secondary metabolites of Streptomyces sp. TRA9851-2 from mangrove sediment

Abstract

In the course of our investigation for bioactive metabolites of the actinomycetes, we isolated an actinomycete strain TRA9851-2 from a sediment sample collected in a mangrove area of Trang Province. Based on morphological, cultural, physiological, biochemical, and cell wall component studies, the strain TRA9851-2 was identified as the genus Streptomyces. The ethyl acetate extract of fermentation broth of the strain significantly inhibited the growth of Bacillus subtilis ATCC 6633, Staphyloccus aureus ATCC 25923, and Candida albicans ATCC 10231. Upon chromatographic separation guided by antimicrobial activity of the ethyl acetate extract yielded two benzo[c,d]pyrenes, resistomycin and a derivative with two possible structures, 9-methyl-4, 6, 8, 10, 11, 11-hexahydroxy-2H-benzo[c,d]pyrene-2,7(1H)-dione or 9-methyl-4, 6, 8, 10-tetrahydroxy-11-nor-2H-benzo[c,d]pyrene-2,7(1H)-dione; a diketopiperazine, cyclo-(propyl-leucyl); and two phenolic acids, syringicacid and p-coumaric acid. The structure elucidation of the isolated substances was achieved by analyses of spectroscopic data including MS, UV, IR, and NMR spectroscopy. Resistomycin exhibited antibacterial activity against Bacillus subtilis ATCC 6633 and toxicity against herpes-simplex viruses type I and type II. Resistomycin possessed potent antimalarial activity against Plasmodium falciparum (K1, multidrug resiststant strain), and also showed cytotoxicity against oral human epidermoid and breast cancer cell lines.