Two triterpenoid saponins from Pterocephalus bretschneidri

Two new triterpenoid saponins, named bretschnosides A and B, were isolated from the roots of Pterocephalus bretschneidri. On the basis of chemical degradation and spectroscopic evidence, the structures of bretschnosides A and B were shown to be 3-O-alpha-L-rhamnopyranosyl(1-->3)- beta-D-xylopyranosyl(1-->3)-alpha-L-rhamnopyranosyl(1-->2)-beta-D- xylopyranosyl oleanolic acid 28-O-beta-D-glucopyranosyl(1-->6)-beta-D-glucopyranoside 4 and 3-O-alpha-D-glucopyranosyl(1-->3)-beta-D-xylopyranosyl(1-->3)-alpha-L- rhamnopyranosyl(1-->2)-beta-D-xylopyranosyl oleanolic acid 28-O-beta-D-glucopyranosyl(1-->6)-beta-D-glucopyranoside 6, respectively.