Bauhinia pulchella: chemical constituents, antioxidant and alpha-glucosidase inhibitory activities.

Phytochemical investigation of the stems of B. pulchella led to the isolation of the known compounds identified as a mixture of taraxerone (1) and β-amirenone (2), a mixture of sitosterol (3) and stigmasterol (4), 2-hydroxy-3,5-dimethoxybibenzyl (5), 3',4'-dihydroxyphenyl-chroman-7-ol (6), fisetinidol (7), epicatechin (8), guibourtinidol (9), vanillic acid (10), 6'-O-vanilloylisotachioside (11) and 6'-O-syringoylisotachioside (12). The structures of these compounds were elucidated on the basis of their NMR spectroscopic data. The antioxidant activity of compound 7 has been investigated using DPPH° and ABTS°+ assays and the results showed inhibition in the both models. The compounds 6, 7 and 9 showed strong alpha-glucosidase inhibitory activities, being more active than acarbose, the positive control. In addition, all the compounds were isolated from B. pulchella for the first time, and among them, compounds 11 and 12 have not been reported previously from this genus.