Green tea catechins, including (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG), are oxidized and dimerized during the manufacture of black tea and oolong tea to form orange-red pigments, theaflavins (TF), a mixture of theaflavin (TF1), theaflavin-3-gallate (TF2A), theaflavin-3*-gallate (TF2B) and theaflavin-3,3*-digallate (TF3). The present study was designed to compare the antioxidant activities of individual TF with that of each catechin using human LDL oxidation as a model. All catechins and TF tested inhibited Cu12-mediated LDL oxidation. Analysis of the thiobarbituric acid-reactive substances (TBARS) and conjugated dienes produced during LDL oxidation revealed that the antioxidant activity was in the order: TF3>ECG>EGCG≥TF2B≥TF2A>TF1≥ EC>EGC. Four TF derivatives also demonstrated a dose-dependent antioxidant activity in Cu+2-mediated LDL oxidation at concentrations of 5-40mmol/L. These results demonstrate that the TF present in black tea possess at least the same antioxidant potency as catechins present in green tea, and that the conversion of catechins to TF during fermentation in making black tea does not alter significantly their freeradical-scavenging activity. J. Nutr. 131: 2248-2251, 2001.

Green tea catechins (GTCs) as a mixture of (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC), and (-)-epigallocatechin gallate (EGCG) possess a variety of biological activities. We have previously studied the stability of GTCs either as a mixture or as individual epicatechin derivatives in various pH, demonstrating that GTCs as a mixture in alkaline solutions were extremely unstable and degraded almost completely in a few minutes, whereas in acidic solutions (pH<4) they were very stable. For the pH ranging from 4 to 7, the stability of GTCs was inversely associated with the pH value of the incubation solutions. The present study examined the effect of ascorbic acid and citric acid on the stability of GTCs incubated in sodium phosphate buffer (pH =7.42). Ascorbic acid added to the incubation mixture significantly increased the stability of GTCs whereas citric acid exhibited no effect. Four epicatechin derivatives examined demonstrated varying stability, with EGCG and EGC being equally instable and EC and ECG being relatively stable. The addition of ascorbic acid significantly increased the stability of all four derivatives, particularly EGC and EGCG. The present results, although not directly transferable to in vivo conditions, may suggest that the presence of ascorbic acid may stabilize the GTCs in the intestine where the pH is neutral or alkaline before absorption.

The present study was to investigate the mechanisms by which hawthorn fruit lowers serum cholesterol in hamsters. The control group was fed a semisynthetic diet containing 0.1% cholesterol while the tested group was maintained on the same diet but supplemented with 0.5% hawthorn fruit aqueous ethanolic extract for 4 weeks. Serum total cholesterol (TC) and triacylglycerols (TG) were decreased by 10 and 13%, respectively, in hawthorn fruit group as compared with the control (P<0.05). Supplementation of hawthorn fruit aqueous ethanolic extract led to greater excretion of both neutral and acidic sterols. Further enzymatic assays suggest the mechanisms by which hawthorn fruit decreases serum cholesterol involve a greater excretion of bile acids mediated by up-regulation of hepatic cholesterol 7α-hydroxylase (CH) activity, and an inhibition of cholesterol absorption mediated by down-regulation of intestinal acyl CoA:cholesterol acyltransferase (ACAT) activity.

The present study examined the hypolipidemic activity of hawthorn fruit. New Zealand white rabbits were fed one of three diets, a reference diet with no cholesterol added (NC), a high cholesterol diet (1g/100g, HC) and a HC diet supplemented with 2g/100g hawthorn fruit powder (HC-H). After 12 wk, serum total cholesterol (TC) and triacylglycerols (TG) were 23.4 and 22.2% lower, respectively, in the hawthorn fruit group compared with the HC rabbits (P﹤0.05). Hawthorn supplementation led to 50.6% less cholesterol accumulation in aorta (P﹤0.05) and 23-95% greater excretion of neutral and acidic sterols (P﹤0.05). Supplementation of hawthorn fruit did not affect the activities of hepatic 3-hydroxy-3-methyl glutaryl coenzyme A reductase (HMG-CoA-R) or cholesterol 7 -hydroxylase (CH) but it suppressed the activity of intestinal acyl CoA:cholesterol acyltransferase (ACAT, P ﹤0.05). The results suggest that the mechanism by which hawthorn fruit decreases serum cholesterol involves, at least in part, the inhibition of cholesterol absorption mediated by down-regulation of intestinal ACAT activity. J. Nutr. 132: 5-10, 2002.

The extract prepared from hawthorn (Crataegus fruit) was examined for its relaxant effect in rat isolated mesenteric arteries. Hawthorn extract induced concentrationdependent relaxation of the U46619-precontracted artery with an IC50 of 0.22