Lactoquinomycin C and D, two new medermycin derivatives from the marine-derived Streptomyces sp. SS17A

AbstractLactoquinomycin C (1) and Lactoquinomycin D (2), two new medermycin derivatives together with six known compounds (3–8) were isolated from the rice solid fermentation of the marine-derived Streptomyces sp. SS17A. The intriguing structural features of the Lactoquinomycin D (2) which contains 5,14-epoxidation is relatively rare in medermycin derivatives. Compounds 1 and 2 exhibited no cytotoxicity against PC-3 and HCT-116 cancer cell lines, whereas compound 3 showed stronger cytotoxicity with IC50 values of 0.02 and 0.04 μM, respectively. A structure-activity relationship was observed for the cytotoxicity of the medermycin derivatives with a γ-lactone unit is required for significant cytotoxicity based on compounds 1–3.