Inhibitory effects of ellagi- and gallotannins on rat intestinal alpha-glucosidase complexes

The clove ellagitannins and their related polygalloylglucoses inhibited mal tase activity of rat intestinal alpha -glucosidases. The structure-activity relationship study of those galloylglucoses, varying the extent of galloyl ation on the glucose core, with the ellagitannins, indicated that an increa sing number of galloyl units in the molecule lead to an increase in the inh ibitory activity. Penta-O-galloyl-beta -D-glucose, with five galloyl groups showed the highest inhibitory activity. On the other hand, hexahydroxydiph enoyl units contained in the ellagitannins had little effect on the activit y. After separation of maltase-glucoamglaas and sucrase-isomaltase complexe s from the crude mixture of the rat alpha -glucosidases, the inhibitory act ivities of the galloylglucose derivatives against each complex were examine d. The inhibitory influence on the maltase-glucoamylase complex was more po tent than on the sucrase-isomaltase complex.