Oleanane-type triterpene saponins from Hydrocotyle nepalensis

Abstract

Five new oleanane-type triterpene saponins including steganogenin 3-O-β-D-glucopyranoside (1), steganogenin 3-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside (2), steganogenin 3-O-β-D-glucopyranosyl-(1→2)-β-D-glucopyranoside (3), chichipegenin 3-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside (4) and chichipegenin 3-O-β-D-glucopyranosyl-(1→2)-β-D-glucopyranoside (5), along with four known oleanane-type triterpenes and triterpene saponins (6-9) were isolated from EtOH extract of the whole plant of Hydrocotyle nepalensis. To the best of our knowledge, oleanane-type triterpenes possessing skeleton with 17, 22-seco-backbone (1-3) are not common in natural products. Compound 8 was isolated as a new natural product. The structures of new compounds were elucidated by extensive spectroscopic methods and chemical evidence. Moreover, the cytotoxic activity of all the isolates against five selected human cancer cell lines (HL-60, SMMC-7721, A-549, MCF-7 and SW480) was evaluated and the results indicated that compounds 6 and 7 show stronger cytotoxic activity.

Keywords: Cytotoxic activity; Hydrocotyle nepalensis; Oleanane-type triterpene saponin.