Thesis (M.Sc. in Pharm.)--Chulalongkorn University, 2007

Glucosidase is the key enzyme which catalyzes the final step in the digestive process of carbohydrates. Hence, -glucosidase inhibitors can retard the liberation of D-glucose from complex dietary carbohydrates and delay glucose absorption, reducing plasma glucose levels. In a preliminary examination of the extracts of Gynura procumbens, the aqueous extract exhibited highest inhibitory activity on ?-glucosidase. Further fractionation of the active aqueous extract by bioassay guidance furnished fractions showing 82.93, 59.41, and 64.21% inhibition on ?-glucosidase at concentration 1mg/ml, respectively. Moreover, a kinetic study was performed on the most active fraction to analyse the inhibition mechanism. The active fractions were treated with acetic anhydride to give 3 acetyl derivatives, GP1, GP2, and GP3, respectively. The structures were determinated by analyses of 1H, 13C and 2D-NMR, IR and mass spectrometry. The results suggested that the present components were [alpha]-D-glucosyl-(1 [vector] 2)-O-psicoside, [alpha]-D-glucosyl-(1 [vector] 2)-O-fructoside and [alpha]-D-galactosyl-(1 [vector] 2)-O-tagatoside, respectively.