Three new triterpenoid saponins from Ixeris sonchifolia and their cytotoxic activity

Bioassay-guided fractionation of an active n-BuOH extract of the whole plant of Ixeris sonchifolia, using a cytotoxicity assay, resulted in the isolation of three new triterpenoid saponins, ixeris saponins A (1), B (2), and C (3). On the basis of chemical evidence and extensive spectral studies, their structures were established as echinocystic acid 3-O-beta-D-glucopyranosyl(1-->3)-beta-D-glucopyranosyl(1-->3)-alpha- L-arabinopyranoside (1), 3-O-[bis[beta-D-glucopyranosyl(1-->2 and 1-->3)-alpha-L-arabinopyranosyl]]echinocystic acid 28-O-beta-D-glucopyranosyl ester (2), and 3- O-[beta-D-glucopyranosyl(1-->3)-beta- D-glucopyranosyl(1-->3)-alpha-L-arabinopyranosyl]-16alpha, 23-dihydroxyolean-12-ene 28-O-beta-D-glucopyranosyl ester (3). Compounds 2 and 3 showed significant cytotoxicity against cancer cell lines A375, L929, and HeLa with IC50 values ranging from 8.83 microM to 15.83 microM, while compound 1 was inactive against these three cell lines.