In vitro and in vivo evaluation of the antidiabetic activity of ursolic acid derivatives.

In this study, a series of ursolic acid derivatives were synthesized, and their structures were confirmed. The activity of the synthesized compounds against α-glucosidase was determined in vitro. The results suggested that all compounds have significant inhibitory activity, especially compounds 3-5 and 8, the IC50 values of which were 2.66 ± 0.84, 1.01 ± 0.44, 3.26 ± 0.22, and 3.24 ± 0.21 μM. These compounds were more potent than acarbose (positive control) against α-glucosidase. Kinetic studies were performed to determine the mechanism of inhibition by compounds 3-5 and 8. The kinetic inhibition studies indicated that compound 3 was a non-competitive inhibitor, and the inhibition constant Ki was calculated to be 2.67 ± 0.19 μM. Moreover, the kinetic inhibition studies of compounds 4, 5 and 8 demonstrated that they were mixed-type inhibitors. Furthermore, the actual pharmacological potentials of synthesized compounds 3 and 4 were demonstrated by the reduction of postprandial blood glucose levels in normal Kunming mice. The hypoglycemic effects of these compounds were more evident 30 and 60 min after maltose ingestion (P < 0.05), which was similar to the effect displayed by the positive control, acarbose.