Difference of inhibitory effect of α-glucosidase by tealeaves species and extraction condition and effect of black tea on postprandial blood glucose level elevation in ICR mice

3) Summary Inhibitory effects in vitro ofα-glucosidase within various kinds of black tea leaves were evaluated. Comparison of 24 different black tea leaves showed that the Uva is the most effective black tea forα-glucosidase inhibition. The Uva tea was extracted in various conditions and their inhibitory effect was compared. The highest activity was obtained in the brewing condition of 4% tea leaves against hot water (80℃), for 3 min. The test on ICR mice revealed that the black tea has significantly inhibitory effect to the elevation of Postprandial blood glucose (PBG) levels caused by the loading of starch, maltose and sucrose. As a result of measurement of total polyphenol quantity of 24 kinds of black tea, positive correlation was shown between total polyphenol quantity and inhibitory effect on α-glucosidase activity of the black tea (p < 0.001). Finally, relationship between chemical component and activity was examined by using of HPLC method. These results indicate that the inhibitory effect of the black tea onα-glucosidase activity is influenced by the difference in tea varieties, and the extrac- tion condition. In addition, it was suggested that the black tea suppressed the elevation of PBG levels, and theaflavin was the main active ingredient of inhibitory effect onα-glucosidase activity among polyphenols of the black tea.