Isolation and characterization of saponins from Castanospermum australe Cunn. et Fraser

Three new triterpenoid saponins, their methyl esters designated as castaralesides F (1), G (2) and H (3), were isolated from the fresh leaves of Castanospermum australe. The structures of these three saponins were elucidated on the basis of chemical and spectral data as 3 beta-O-[beta-galactopyranosyl-(1-->4)-beta-glucuronopyranosyl]-2 beta,23-dihydroxyolean-12-en-28-oic acid; 3 beta-O-[alpha-rhamnopyranosyl-(1-->4)-beta-galactopyranosyl-(1-->2)-beta - glucurono-pyranosyl]-2 beta,28-dihydroxyolean-12-ene; and 3 beta-O-[alpha-rhamnopyranosyl-(1-->4)-beta-xylopyranosyl-(1-->2)-beta- glucuronopyranosyl]-2 beta,28-dihydroxyolean-12-ene.