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.