Triterpenoid saponins from stem bark of Pentaclethra macroloba

Abstract

Two new and two known triterpenoid saponins were isolated from the stem bark of Pentaclethra macroloba. Their structures were determined using a combination of homo- (1D 1H NMR, 13C NMR-HBBD and 13C NMR-DEPT) and heteronuclear 2D NMR techniques ( 1H-1H-COSY, 1H-1H-TOCSY, 1H-1H-NOESY, HMQC and HMBC), ESIMS and chemical methods. The structures of the two new pentacyclic triterpenoid saponins were established as 3β-O-{[β-D-glucopyranosyl-(1→3)-α-L-rhamnopyranosy]- (1→2)],β-D-glucopyranosyl-(1→4)}-α-L- arabinopyranosylhederagenin (3) and 3β-O-{[β-D-glucopyranosyl- (1→4)-β-D-glucopyranosyl-(1→3)-α-L-rhamnopyranosyl- (1→2)],β-D-glucopyranosyl(1→4)}-α-L- arabinopyranosyloleanolic acid (4).