Abstract
Although the major green tea catechins can inhibit the activity of carbohydrate-hydrolyzing enzymes, there is a paucity of information describing the potential of other green tea ingredients and numerous green tea cultivars. Herein, we reveled that a green tea cultivar Sunrouge significantly suppressed the postprandial blood glucose level in mice. Unlike the most representative Japanese green tea cultivar, Yabukita, the suppression by Sunrouge was observed clearly during the initial period after oral dosing of starch. Sunrouge also strongly inhibited the carbohydrate-hydrolyzing enzymes α-glucosidase and α-amylase when compared with that of Yabukita and many other cultivars. Liquid chromatography–mass spectrometry (LC–MS)-based metabolic profiling (MP) of 42 Japanese green tea cultivars was performed. Multivariate statistical analysis enabled visualization of the differences among cultivars with respect to their ability to inhibit carbohydrate-hydrolyzing activities. Analysis of metabolites, contributing to the discrimination and prediction of the bioactivity of cultivars, showed that O-methylated catechins, epicatechin-3-O-(3-O-methyl) gallate (ECG3”Me) and epigallocatechin-3-O-(3-O-methyl) gallate (EGCG3”Me), were newly identified α-glucosidase inhibitors. Such ability was also observed in epigallocatechin-3-O-gallate (EGCG), epicatechin-3-O-gallate (ECG), delphinidin-3-O-glucoside and myricetin-3-O-glucoside. The amounts of these compounds in Sunrouge were higher than that in many other cultivars. These results suggest that Sunrouge has high potential for suppressing the elevation of the postprandial blood glucose level, and an MP approach may become a valuable strategy for evaluating the anti-hyperglycemic activity of green tea and for screening its active ingredients.
Highlights
Diabetes is currently one of the most significant public health challenges worldwide
The results showed unequivocally that the Sunrouge (500 mg/kg b.w) was superior in inhibiting the postprandial blood glucose level when compared with the Yabukita cultivar
We have demonstrated for the first time that a metabolomics approach, cultivar-specific Metabolic profiling (MP), can be used to evaluate the hypoglycemic-related activity of various Japanese green tea cultivars and to identify bioactive factors
Summary
Diabetes is currently one of the most significant public health challenges worldwide. Previous research suggested that food-derived phenolic compounds could delay glucose absorption by inhibition of carbohydrate-hydrolyzing enzymes, which would reduce the postprandial blood glucose level. This could be a suitable approach to treat and prevent type 2 diabetes[3]. We investigated the feeding effect of the Japanese green tea cultivar, Sunrouge, on the postprandial blood glucose level in mice and attempted to screen the active ingredients to identify an inhibitor of carbohydrate-hydrolyzing enzymes from Sunrouge by cultivar-specific MP-based data-mining technique
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