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-glucopyranoside; 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.