Sinulasterols D–G, four new antibacterial steroids from the South China sea soft coral Sinularia depressa

Abstract

Four new steroids, namely sinulasterols D–G (1–4), along with seven known related ones 5–11, were isolated from the Xisha soft coral Sinularia depressa. The structures of the new compounds were elucidated by a combination of extensive spectroscopic analyses, chemical conversion method, and comparison of the NMR data with those of known analogues. In in vitro bioassays, compounds 1–3 showed significant antibacterial activities against gram-positive bacteria Enterococcus faecium with minimum inhibitory concentration (MIC) values of 62.5, 125, and 125 µM, respectively, comparable with that of vancomycin (MIC: >44.2 µM).