Pregnane steroids from the twigs and leaves of Strophanthus divaricatus and their cytotoxic activities

Four new pregnanes (1–4), including one 21-norpregnane (4), together with two known pregnanes (5 and 6), were isolated from the twigs and leaves of Strophanthus divaricatus. Their structures were elucidated on the basis of spectroscopic data analysis, ECD data, and X-ray crystallographic study. The cytotoxic activities of these pregnanes against two human cancer cell lines were evaluated.