Study On Hypoglycemic Activity Of Green Tea Extract

During the last century, rapid social development and changes in human lifestyle have resulted in a dramatic increase in the prevalence of diabetes mellitus in the world, which is a serious threat to human health. Though oral hypoglycemic agents and insulin are the main ways of treatment for diabetes, they have somewhat side effects. So it is very urgent for us to develop anti-diabetic plants for its less toxicity and no-drug-resistance. Green tea is a widely consumed beverage for centuries, especially in Asia. The chemical composition of green tea is complex. Green tea is often associated with the control of diabetes and diabetes complications. However, the available evidences are not conclusive. In this study, we relatively systematically assessed the contribution of main green tea extract (GTE) ingredients to the effects of postprandial blood glucose control.Firstly, this research is designed to study the comprehensive extraction of tea polyphenols and tea polysaccharides from green tea, then prepare the green tea extract following this optimum extraction conditions. Using the method of HPLC to measure the content of the following main components, which are (-)-Gallocatechin (GC),(-)-Epicatechin (EC),(-)-Catechin (C),(-)-Epigallocatechin (EGC),(-)-Epigallocatechin gallate (EGCG),(-)-Gallocatechin gallate (GCG),(-)-Epicatechin gallate (ECG), catechin-3-gallate (CG), and Caffeine. According to the contents of these eight kinds of catechins in green tea extract, prepared mixed solution of these eight kinds of catechins (CM) and EGCG solution.Secondly, the inhibitory potency of GTE and main green tea extract (GTE) ingredients on a-amylase and a-glucosidase was compared, and there comes out similar inhibition between crude polyphenols and GTE. Measured and compared the IC50of GTE and the main components againsta-amylase and a-glucosidase, and also compared the inhibitory potency of GTE, CM and EGCG on a-amylase and a-glucosidase. It turns out that catechins are the mian components inhibiting both a-amylase and a-glucosidase in green tea extract, and EGCG plays a very important role as it is the highest content in the catechins. On this basis, measured the inhibitory kinetic of EGCG ona-amylase and a-glucosidase. The results reflected that the inhibition type of EGCG is non-competitive inhibition.Moreover, the inhibitory potency of samples on glucose transport was assessed in Caco-2cell monolayer system. After compared the inhibitory potency of GTE and green tea extract ingredients on glucose transport, the inhibitory potencies of GTE, CM and EGCG are investigated under the simulated fasting state and stimulated fed state. And the inhibitory efficacy was decreased with GTE>CM> EGCG when the concentration of EGCG is the same.