Alpha-Amylase Inhibitors in Galla Chinensis

In order to separate the inhibitory factors of α-amylase in Galla Chinensis,crude methanol extract of Galla Chinensis was fractionated by sequential Soxhlet extraction with petroleum ether,ethyl ether,ethyl acetate and methanol.Meanwhile,the residue left after methanol extraction was extracted with acetone-water(1:1,V/V) and the extract obtained was further separated by pH gradient extraction,polyamide column chromatography and Seaphadex LH-20,respectively.The inhibitory activity of all samples against α-amylase was determined.The results showed that the inhibitory rates of ethyl ether fraction,ethyl acetate fraction,acetone-water extract,methanol faction(obtained from secondary extraction by Soxhlet method),petroleum ether fraction and crude methanol extract were 91.04%,90.38%,80.09%,66.48%,34.14% and 23.96%,respectively.The α-amylase inhibitors in petroleum ether fraction were lauric acid,myristic acid and palmitic acid with corresponding inhibitory rates of 34.34%,31.71% and 31.01%,respectively.Tannic acid and gallic acid were the α-amylase inhibitors in ethyl ether fraction,with corresponding inhibitory rates of 66.7% and 21.3%,respectively.The α-amylase inhibitor composition in acetone-water extract was complicated and consisted of partially methyl-esterified fatty alcohols according to preliminary purification and GC-MS analysis.