A new bioactive aminophenoxazinone alkaloid from a marine-derived actinomycete

Chemical investigation of the marine Streptomyces sp. Eg25 led to the isolation of one new natural 2-aminophenoxazin-3-one-8-carboxylic acid methyl ester named maroxazinone (1) as well as the known compounds elloxazinone A (2), exfoliazone (3), carboxyexfoliazone (4), elloxazinone B (5) and venezueline D (6). The chemical structures of the isolated compounds were deduced from extensive studies of NMR (H-1 and C-13 NMR, H-1-H-1 COSY, HMQC and HMBC) and mass spectra. The cytotoxic activities of the new maroxazinone (1) and venezueline D (6) against breast carcinoma cell line (MCF7), liver carcinoma cell line (HEPG2) and colon carcinoma cell line (HCT116) were investigated.