Withanolides isolated from Withania somnifera with α-glucosidase inhibition

Phytochemical investigations on the chloroform soluble fraction of the whole plant of Withania somnifera led to the isolation of 20 beta hydroxy-1-oxo(22R)-witha-2,5,24 trienolide 1, (20R, 22R-14 alpha, 20 alpha)-dihydroxy-1-oxowitha-2,5,16,24 tetraenolide 2, and (20R, 22R)-1-oxo-5 alpha, 8 beta-dihydroxywitha-6 alpha, 7 beta-epoxide-2,24-dienolide (withasomilide) 3. The structures of these compounds were confirmed through spectral studies in comparison with data in the literature. These isolated compounds (1-3) exhibited potent inhibition against alpha-glucosidase with IC50 values of 98.60, 38.20, and 40.65 mu g/ml respectively.