Stimulation of glucose uptake by triterpenoids from Weigela subsessilis.

Four ursane-type triterpenoids, corosolic acid (1), ilekudinol B (2), ursolic acid (3) and pomolic acid (4), were isolated from an EtOAc-soluble extract of the leaves of Weigela subsessilis. These bioactive compounds were evaluated for their glucose uptake activity and produced moderate to strong enhancement both in basal- and insulin-stimulated L6 muscle cells. In particular, corosolic acid exhibited the most potent activity, increasing uptake by basal- and insulin-stimulated myotubes by 2.63- and 3.33-fold, respectively; ilekudinol B produced 1.6- and 2.9-fold, ursolic acid produced 1.84- and 2.64-fold, and pomolic acid produced 1.6- and 2.8-fold increases. No cytotoxicities were observed for corosolic acid, ursolic acid and ilekudinol B in myoblasts, while pomolic acid at doses of 25 and 50 microm reduced cell viability by 19% and 21.8% upon 24 h treatment and by 48.6% and 54.1% upon 48 h treatment, respectively. These results suggest that ursane-type triterpenoids from W. subsessilis might enhance glucose uptake by acting as insulin mimics and as insulin sensitizers and that they could be useful as nontoxic diabetes treatment agents. (c) 2009 John Wiley & Sons, Ltd.