Five new medicagenic acid saponins from Muraltia ononidifolia

Abstract

Five new triterpene saponins 1-5 were isolated from the roots of Muraltia ononidifolia E. MEY along with the two known saponins 3-O-[O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosyl]medicagenic acid 28-[O-β-D-xylopyranosyl-(1 → 4)-O-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl] ester and 3-O-(β-D-glucopyranosyl)medicagenic acid 28-[O-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl] ester (medicagenic acid = (4α,2β,3β)-2,3-dihydroxyolean-12-ene-23,28-dioic acid). Their structures were elucidated mainly by spectroscopic experiments, including 2D-NMR techniques, as 3-O-(β-D-glucopyranosyl)medicagenic acid 28-[O-β-D-apiofuranosyl-(1 → 3)-O-β-D-xylopyranosyl-(1 →4)-O-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl] ester (1), 3-O-(β-D-glucopyranosyl)medicagenic acid 28-{[O-β-D-xylopyranosyl-(1 → 4)-O-[β-D-apiofuranosyl-(1 → 3)]-O-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl} ester (2), 3-O-[O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosyl]medicagenic acid 28-{O-β-D-xylopyranosyl-(1 → 4)-O-[β-D-apiofuranosyl-(1 → 3)]-O-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl} ester (3), 3-O-[O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosyl]medicagenic acid 28-[O-α-L-rhamnopyranosyl-(1 →-arabinopyranosyl] ester (4), and 3-O-[O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosyl] medicagenic acid (5).