Gephyyamycin and cysrabelomycin, two new angucyclinone derivatives from the Streptomyces sp. HN-A124

Gephyyamycin (1) owned the rare 3,12a-epoxybenz[a]anthracene ring system, and cysrabelomycin (2) possessed an acetylated cysteine group, two new angucyclinone derivatives were isolated from the rice solid fermentation of the marine-derived Streptomyces sp. HN-A124, an actinobacterium isolated from the marine sediments collected from Hainan Province, China. Their structures were elucidated on the basis of MS, NMR spectroscopic, X-ray diffration data analyses and quantum chemical calculations of the electronic circular dichroism (ECD) spectra. Compound 2 appeared to show moderate cytotoxicity against human prostate cancer PC3 and human ovarian carcinoma A2780 cell lines with IC50 values of 19.39 and 10.23 μM, respectively; on the other hand, compound 2 also exhibited moderate antibacterial activities against Staphylococcus aureus and Candida albicans with an MIC value of 20.0 and 20 μM, respectively.