Quinovic acid glycosides from Mitragyna stipulosa--first examples of natural inhibitors of snake venom phosphodiesterase I

Phytochemical investigations on the non-alkaloidal extracts of Mitragyna stipulosa bark has led to the isolation of a series of triterpenoids mainly consisting of quinovic acid (structure: see text]) and its glycoside derivatives structure: see text] and structure: see text]. The other constituents isolated include alpha-amyrin, 3beta-acetyl ursolic acid and a mixture of oleanolic and ursolic acid and beta-sitosterol glucopyranoside. Their structures were identified by spectral and chemical studies and compounds structure: see text] and structure: see text] were, respectively, identified as quinovic acid 3-O-beta-D-glucopyranoside] (quinovin glycoside C) and quinovic acid 3-O-beta-D-quinovopyranoside]-27-O-beta-D-glucopyranosyl] ester. Compounds structure: see text] and structure: see text] showed significant inhibitory activity against snake venom phosphodiesterase I.