Flavonol Caffeoylglycosides as α-Glucosidase Inhibitors from Spiraea cantoniensis Flower

Abstract

In the screening experiments for rat intestinal alpha-glucosidase inhibitors in 218 plants cultivated in the Japanese temperate region, potent maltase-inhibiting activity was found in the extract of flowers of Spiraea cantoniensis. The enzyme assay guided fractionation of the extract led to the isolation of three flavonol caffeoylglycosides, quercetin 3- O-(6- O-caffeoyl)-beta-galactoside ( 1), kaempferol 3- O-(6- O-caffeoyl)-beta-galactoside ( 2), and kaempferol 3- O-(6- O-caffeoyl)-beta-glucoside ( 3), as rat intestinal maltase inhibitors. This is the first report on the alpha-glucosidase-inhibitory activity of those flavonol caffeoylglycosides. Comparison in the activity of the isolates indicated the importance of caffeoyl substructures in the molecule for the alpha-glucosidase-inhibiting activity. The relatively high contents of the active isolates in the plant suggest that S. cantoniensis could be physiologically useful for treatment of diabetes.

Methyl Caffeate as an α-Glucosidase Inhibitor fromSolanum torvumFruits and the Activity of Related Compounds

“…Sucraseand maltase-inhibitory activities indicating inhibition of sucrase-and maltase-hydrolyzing activities respectively in rat intestinal glucosidase complexes were measured as described previously. 7) Briefly, a crude enzyme solution prepared from rat intestinal acetone powder (SigmaAldrich Japan, Tokyo) was used as the small intestinal -glucosidase. A reaction mixture consisting of crude enzyme solution (0.05 ml of maltase or 0.2 ml of sucrase), substrate solution (0.35 ml of 3.5 mM y To whom correspondence should be addressed.…”

“…It is caused by continual hyperglycemia and develops along with increases in obesity and aging in the general population. 1) One of the therapeutic approaches to decreasing postprandial hyperglycemia is to retard absorption of glucose by inhibition of carbohydrate hydrolyzing enzymes -amylase and -glucosidase in the digestive organs.2) In recent years, many efforts have been made to search for effective -glucosidase inhibitors from natural sources in order to develop a physiological functional food or to discover lead compounds for medicinal usage against diabetes.3) In the course of our search for rat intestinal -glucosidaseinhibiting principles from various plants, we have isolated and identified several active compounds from plants grown in Asian regions, including Japan, [4][5][6][7] Thailand, 8,9) China, 10,11) and Nepal. 12) In this paper, we present the results of a screening of plants cultivated in Tanegashima, a southern island of Japan, for rat intestinal -glucosidase inhibition.…”

“…Separation of S. torvum fruit extract using various column chromatographic techniques lead to the isolation of methyl caffeate (1) as one of active principles. Some -glucosidase inhibitors previously isolated from plants contain the caffeoyl moiety as the part of their structure and have been found to be important in exerting inhibitory activity, 3,7) but the contribution of an ester part to the -glucosidase-inhibitory activity of caffeic esters has not been studied. Hence we also present comparative results for -glucosidase inhibition of various synthetic caffeic esters and related compounds.…”

“…3) In the course of our search for rat intestinal -glucosidaseinhibiting principles from various plants, we have isolated and identified several active compounds from plants grown in Asian regions, including Japan, [4][5][6][7] Thailand, 8,9) China, 10,11) and Nepal. 12) In this paper, we present the results of a screening of plants cultivated in Tanegashima, a southern island of Japan, for rat intestinal -glucosidase inhibition.…”

“…2) In recent years, many efforts have been made to search for effective -glucosidase inhibitors from natural sources in order to develop a physiological functional food or to discover lead compounds for medicinal usage against diabetes. 3) In the course of our search for rat intestinal -glucosidaseinhibiting principles from various plants, we have isolated and identified several active compounds from plants grown in Asian regions, including Japan, [4][5][6][7] Thailand, 8,9) China, 10,11) and Nepal. 12) In this paper, we present the results of a screening of plants cultivated in Tanegashima, a southern island of Japan, for rat intestinal -glucosidase inhibition.…”