Effects of Green Tea on Activity of A-Glucosidase in Vitro and Glycaemic Index of White Bread in Vivo

Activities of ?-glucosidase enzyme and high glycaemic index diet have been implicated in postprandial hyperglycaemia, the control of which might be useful in curbing diabetes mellitus. Some herbs have been reported to show inhibitory activities against carbohydrate digesting enzymes (such as ?-glucosidase) and lower the glycaemic index of a carbohydrate-rich diet. In the present study, lowering effect of green tea (Camellia sinensis) on ?-glucosidase activity and on the glycaemic index of white bread were investigated in-vitro and in-vivo respectively. For in-vitro study, ?-glucosidase enzyme was incubated with substrate (p-nitrophenyl glucopyranoside) in the absence and presence of inhibitor (green tea) and its activity was investigated. Thirty (30) healthy participants were involved in the in vivo study of glycaemic index. Ten-hour fasting blood glucose levels of the participants were taken before they took bread and tea and then the postprandial glucose levels were taken at 15, 30, 45, 60, 90 and 120 minutes accordingly. The results of this study revealed that the green tea lowered the activity of ?-glucosidase to 17.50% with IC50 of 200.30?g/mL and Ki of 113.04?g/mL. It also lowers the glycaemic index of white bread (85.51%) to 33.95% when bread consumption was delayed for 5 minutes after taking the tea. In conclusion, this study shows that green tea can be used to lower the postprandial blood glucose level which might be beneficial in the control and management of diabetes mellitus.