Isolation and structure of five new cancer cell growth inhibitory bufadienolides from the Chinese traditional drug Ch'an Su.

Five new bufadienolides, 3beta-formyloxyresibufogenin (1), 19-oxobufalin (2), 19-oxodesacetylcinobufagin (3), 6alpha-hydroxycinobufagin (4), and 1beta-hydroxybufalin (5), have been isolated together with the previously known bufadienolides 6-20 from the Chinese traditional drug "Ch'an Su". The structures were elucidated employing spectroscopic methods. Bufadienolides 1-5 provided significant inhibitory activity against the KB and HL-60 cancer cell lines. In addition, bufadienolide 1 was found active against the MH-60 cancer cell line.