Cytotoxic constituents of chinese propolis.

A pair of new flavanol racemates (1a and 1b) and a new flavanol racemic mixture (2) were isolated from crude propolis from Henan Province, People's Republic of China. Also obtained were nine known compounds, including two flavones, four flavonols, two flavanols, and isoferulic acid. Spectroscopic analysis was employed to assign the structures of these new compounds and the absolute configurations of 1a and 1b. Cytotoxicity of the isolated compounds against the HeLa human cervical carcinoma cancer cell line was evaluated, with only compounds 1a, 1b, 2, and rhamnetin (3) being active.