Bioactive constituents from marine-derived Streptomyces sp. NB-A13

Abstract Six new anthracyclines (1-6) were obtained by the investigation of the solid fermented extract of a marine-derived Streptomyces sp. NB-A13. The structures were elucidated on the basis of spectroscopic analysis, including 1D and 2D NMR, HRESIMS, UV and IR. The absolute configurations of compounds 1-5 were established by calculated electronic circular dichroism (ECD) using time dependent density functional theory. Among the isolates, four compounds (2, 3, 5 and 6) showed moderate cytotoxic activity against PC3 cells (prostate cancer cells) with IC 50 values of 7.0 ± 0.3 μM, 0.92 ± 0.05 μM, 2.1 ± 0.7 μM and 9.8 ± 0.7 μM, respectively.