Inhibitory effect of jasmine green tea epicatechin isomers on LDL-oxidation

Oxidative modification of low-density lipoproteins (LDL) is thought to play an important role in the development of atherosclerosis. The present study examined inhibitory effect of jasmine green tea polyphel (GTP) extracts and its individual epicatechin isomers on Cu+2-mediated oxidation of human LDL. The jasmine tea GTP extracts consisted mainly of four epicatechin isomers with (-) epigallocatehin gallage (EGCG) being most abundant (51.2%) followed by (-) epigallocatechin (EGC, 18.7%), (-) epicatechin (EC, 12.3%), and (-) epicatechin gallate (ECG, 11.8%). Jasmine tea GTP as a mixture or its four epicatechin isomers demonstrated strong antioxidant activity in Cu+2-mediated oxidation of human LDL. The inhibitory effect of these epicatechin isomers on LDL oxidation was dose-dependent at the concentrations ranging from 5 to 40 mu m. EC and EGC were less protective against LDL oxidation than their gallate derivatives, ECG and EGCG, respectively. ECG and EGCG seemed to have a similar antioxidant activity. In contrast, EGC was less effective than EC as an antioxidant against LDL oxidation. The inhinitory effect of jasmine green tea epicatechin isomers on Cu+2-mediated oxidation was also characterized by protecting docosahexaenoic, arachidonic, alpha-linolenic, and linoleic acid in LDL against oxidative degradation. We conclude that, in addition to their hypocholesterolemic effect, jasmine tea epicatechin isomers may serve as a source of natural antioxidative agents in human diet.