α-Glucosidase inhibitory triterpenoids from the stem barks of Uncaria laevigata.

A phytochemical study on the ethanolic extract of the stem barks of Uncaria laevigata leads to the isolation and characterization of 18 triterpenoid compounds. Ten of these are new, including one novel heptanortriterpenoid (1), four ursane triterpenes (2-4, 10), and five oleanane triterpenes (5-9). Their structures were established by spectroscopic methods, especially by 2D-NMR and MS analyses. All these isolates were evaluated for their inhibitory effects on α-glucosidase: ursolic acid and 3 showed potent activities with IC₅₀ values of 16 ± 2.2 and 49 ± 3.7 μM, respectively.