Bioactivity-guided chemical analysis of Melia azedarach L. (Meliaceae), displaying antidiabetic activity.

One new Euphane-type triterpenoid 3ß-hydroxytirucalla-5, 24-dien-21-oic acid (1), and ten known compounds (2-11) were isolated from Melia azedarach L. through bioassay-guided chemical analysis. The structures of the isolated compounds were established by means of 1D and 2D NMR spectroscopic ((1)H, (13)C, DEPT, COSY, HSQC and HMBC) and MS spectral analyses. All the fractions and isolated pure compounds were evaluated for antidiabetic activity by determining their inhibitory effects on PTP-1B enzyme as well as glucose uptake stimulation in C2Cl2 myoblasts cells. Compounds 4 and 7 showed significant in vitro PTP-1B inhibitory activity with 69.2 and 66.8% inhibition at 10 µg/ml concentrations respectively.