| Green tea contains about 10% tea catechins mainly including (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG) and (-)-epigallocatechin gallate (EGCG). Tea catechins have been shown to be hypocholesterolemic, anticarcinogenic, antioxidative and antibacterial. Recently, canned and bottled tea drinks are getting popular worldwide. However, HPLC analysis revealed that canned and bottled tea drinks were relatively low in tea catechins but they were abundant in catechin epimers, namely (-)-catechin (C), (-)-gallocatechin (GC), (-)-catechin gallate (CG) and (-)-gallocatechin gallate (GCG). In the present study, the epimerization of tea catechins as well as their antioxidant potency, absorption pattern, metabolites and anti-obesity property were investigated.; To compare the biological activity of these epimers with their precursors, four tea catechins and four epimers were isolated from Longjing tea infusion. Isolation and purification of each tea catechin and epimer were accomplished by various column chromatographic and semi-preparative HPLC techniques. The antioxidant activity of each epimer with its corresponding tea catechin precursor was conducted in the three in vitro systems, namely human low-density lipoprotein (LDL) oxidation, ferric reducing-antioxidant power (FRAP), and anti-DPPH free radical assays. It was concluded that epimerization reaction occurred in manufacturing canned and bottled tea drinks would not affect significantly antioxidant activity and absorption of total tea polyphenols.; The anti-obesity effect of tea extract was studied in Sprague-Dawley rats. The results clearly demonstrated that anti-obesity effects of tea catechins (containing 8% EGC, 7% EC, 68% EGCG and 12% ECG of total tea catechins) on rats were dose dependent. The consumption of 200 mg/kg body weight of tea catechins efficiently decreased the body weight as well as weight of total fat pads (sum of epididymal, inguinal and perirenal fats) compared with the control group. It was also found that tea catechins were efficient in reducing body weight and the weight of adipose tissue in both male and female rats. (Abstract shortened by UMI.)... |
