AIM: To study the bufadienolides in the Chinese traditional drug "Ch'an Su" and their cytotoxic activity. METHOD: Various chromatographic techniques were used to isolate the constituents, and their structures were elucidated through physical and spectroscopic data. RESULTS: Twenty compounds were isolated, and eighteen were evaluated in vitro for their cytotoxic activity against A-549 and K-562 cells. CONCLUSION: Compound 1(bufalin 3β-acrylic ester) was a new bufadienolide and exhibited the most potent activity against the two tumor cell lines with IC50 values of 7.16 and 6.83 nmol·L–1. The relationships between structure and activity are discussed.
