Studies on the constituents of Clematis species. VIII. Triterpenoid saponins from the aerial part of Clematis tibetana KUNTZ.

From the aerial part of Clematis tibetana, two new hederagenin 3,28-O-bisdesmosides called clematibetosides A and C, and a new gypsogenin 3,28-O-bisdesmoside called clematibetoside B, have been isolated together with ten known saponins. The structures of the new saponins have been elucidated based on chemical and spectral evidence as follows: clematibetoside A, 3-O-(2-O-caffeoyl)-beta-D-glucopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->4)-beta-D-ribopyranosyl-(1-->3)-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl hederagenin 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyraside; clematibetoside B, 3-O-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl gypsogenin 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside; clematibetoside C, 3-O-beta-D-ribopyranosyl hederagenin 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside.