Bidesmosidic oleanane saponins from Xerospermum noronhianum

Abstract

Three new oleanane-type triterpenoid saponins, 3-O-(α-L- rhamnopyranosyl(1 → 2)-β-D-fucopyranosyl)-28-O-{[α-L- rhamnopyranosyl(1 → 2)] [β-D-fucopyranosyl(1 → 6)]-β-D-glucopyranosyl} oleanolic acid (1), 3-O-[α-L- rhamnopyranosyl(1 → 3)-β-D-fucopyranosyl]-28-O-[α-L- rhamnopyranosyl(1 → 4)-β-D-glucopyranosyl] oleanolic acid (2), and 3-O-{α-L-rhamnopyranosyl(1 → 2)-[3′,4′-diacetoxy-β- D-fucopyranosyl]}-28-O-[β-L-rhamnopyranosyl(1 → 2)-β-D- glucopyranosyl] oleanolic acid (3) have been isolated from the stems of Xerospermum noronhianum. The structures of the saponins were determined as a series of bidesmosidic oleanane saponins based on spectral evidence. The anticholinesterase activity of the saponins 1-3 was also evaluated. © 2009 Verlag Helvetica Chimica Acta AG.