New cytotoxic ergostane-type sterols from the Chinese soft coral Sinularia sp.

Two new highly oxygenated ergostane-type sterols (1, 2) together with one known related compound sinugrandisterol A (3) were isolated from the soft coral Sinularia sp. collected from the water area near the Xisha Islands, South China Sea. Their structures were elucidated on the basis of detailed spectroscopic analysis, chemical transformations, and by comparison with those reported in literature. In bioassays, compounds 1 and 2 showed in vitro antiproliferative activity against a panel of cancer cell lines, including MDA-MB-436, A549, Hep3B, HT-29 and H157. Morphological observation and Hoechst 33,258 staining assays showed that compound 1-treated H157 cells displayed apoptosis characteristics. Moreover, western blot assays suggested that 1 could increase the expression of Bax and down-regulate expression of Bcl-2.