Cytotoxic activity of cardenolides from Beaumontia brevituba stems.

Five known cardenolides, digitoxigenin (1), oleandrigenin (2), digitoxigenin alpha-L-cymaroside (3), digitoxigenin beta-gentiobiosyl-alpha-L-cymaroside (4), and delta 16-digitoxigenin beta-D-glucosyl-alpha-L-cymaroside (5), were isolated from the stems of Beaumontia brevituba Oliver by cytotoxicity-directed fractionation monitored by a cultured human lung cancer cell line. The cytotoxic activity of these compounds was evaluated with a panel of twelve human and murine cancer cell lines. The lignan glycoside, syringaresinol beta-D-glucoside, was obtained for the first time in the form of its levo-enantiomer.