Alpha-glucosidase is an important target for
glycemic control with the aim of reducing the risk of
type 2 diabetes (T2D).
Green tea catechins have been reported to inhibit
alpha-glucosidase activity as a potential beverage to
control blood glucose levels. However, the effects of the daily infusion style of
green tea on
tea catechins and their activity remain unclear. In this study, the extraction efficiency of catechins was investigated for 12
green tea extracts (GTEs) infused with 70%
ethanol (70% EtOH for 24 h, a favored
solvent for
catechin extraction), room temperature water infusion (RT H2O for 24 h, an easy way to drink
tea), and hot water infusion (Hot H2O for 90 s, a standard way to drink
tea). Eight catechins were quantified by HPLC, and the inhibitory effect of GTEs and their catechins on
alpha-glucosidase was measured with both rat intestinal
enzymes and human Caco-2 cells. The inhibitory mechanism was further analyzed in silico by docking catechins to human
alpha-glucosidase using Molecular Operating Environment software. The results showed that total catechins and gallate catechins were efficiently extracted in the order of 70% EtOH, RT H2O, and Hot H2O, and the inhibitory activity against
alpha-glucosidase also followed a similar order. Pearson correlation analysis indicated that the
alpha-glucosidase inhibitory activity of GTEs was significantly positively correlated with the contents of total catechins, especially gallate catechins. Gallate catechins, such as EGCg and ECg, showed lower IC50 values than free catechins for the
enzyme in both rats and humans. In silico simulation revealed that gallate catechins were bound to the different sites with free catechins, and the docking energy of gallate catechins was lower than that of free catechins. Taken together, our data indicated that the daily infusion style of
green tea significantly impacted the extraction efficiency and
alpha-glucosidase inhibitory activities of catechins, which will give us insight into the use of
green tea catechins for
glycemic control through efficient infusion.