Saponins from the roots of Zygophyllum gaetulum and their effects on electrically-stimulated guinea-pig ileum.

A new ursanolide, 3beta-O-alpha-L-rhamnopyranosyl-(1->2)-O-alpha-L-arabinopyranosyl-(1->2)-beta-D-glucopyranosyl)oxy]-ursan-20beta,28-olide, zygophyloside N (1), and three known quinovic acid glycosides were isolated from the methanolic extract of the roots of Zygophyllum gaetulum. The crude extract, some fractions and 3-O-beta-D-glucopyranosyl quinovic acid 28-beta-D-glucopyranosyl ester, significantly and dose-dependently, are able to reduce the electrically-induced contractions of isolated guinea-pig ileum. The structure of compound (1) was determined, using 1D and 2D NMR techniques.