Cytotoxic furostanol saponins and a megastigmane glucoside from Tribulus parvispinus

Abstract

Two new furostanol saponins, (25R)-26-O-β-D-glucopyranosyl-5α- furostan-2α,3β,22α,26-tetraol 3-O-{β-D-galactopyranosyl- (1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β-D-glucopyranosyl- (1→4)-β-D-galactopyranoside} (1) and (25R)-26-O-β-D- glucopyranosyl-5α-furostan-3β,22α,26-triol 3-O-{β-D- galactopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)] -O-β-D-glucopyranosyl-(1→4)-β-D-galactopyranoside} (2), and their O-methyl derivatives (3 and 4), and a new megastigmane glucoside, (6S,7E,9ξ)-6,9,10-trihydroxy-4,7-megastigmadien-3-one 10-O-β-D- glucopyranoside (6), along with one known spirostanol saponin, gitonin (5), and four known megastigmane glucosides were isolated from the aerial parts of Tribulus parvispinus. Their structures were established by detailed spectroscopic analysis. The cytotoxic activities of 1-6 against U937, MCF7, and HepG2 cells were evaluated. Compounds 2 (IC50 0.5 μM) and 5 (IC50 0.1 μM) showed the highest activity against U937 cells. © 2005 American Chemical Society and American Society of Pharmacognosy.