Two new cytotoxic pregnane glycosides from Cynanchum auriculatum

Two new pregnane glycosides, kidjoranin 3- O- alpha-diginopyranosyl-(1-->4)- beta-cymaropyranoside (1) and kidjoranin 3-O-beta-digitoxopyranoside (2), together with one known compound caudatin 3 -O-beta-cymaropyranoside (3), were isolated from the roots of Cynanchum auriculatum. Their structures were established on the basis of NMR analyses. Compounds 1 - 3 were tested for their in vitro inhibitory activity against the growth of human tumor cell lines SMMC-7721, HeLa and MCF7; all of them displayed marked cytotoxic activities against cells SMMC-7721 and HeLa with IC (50) values ranging from 8.6 microM to 58.5 microM, yet no activity against the cell line MCF7 was detected.