Nonalcoholic red wine extract and quercetin inhibit LDL oxidation without affecting plasma antioxidant vitamin and carotenoid concentrations

Background: Antioxidant enrichment of LDL can increase its resistance to ox idation and hence reduce its atherogenicity. The objective of the present s tudy was to investigate whether in vivo supplementation with nonalcoholic r ed wine extract and quercetin can increase the oxidative resistance of LDL, and also whether the supplementation has any effect on other antioxidative micronutrients present in the blood. Methods: Twenty-one male subjects were supplemented with a placebo drink fo r 2 weeks and randomized into two groups. One group (n = 11) received the r ed wine extract (1 g/day, equivalent to 375 mL, of red wine) and the other group (n = 10) quercetin (30 mg/day) for 2 weeks, followed by a 5-week wash out period. Results: In the red wine extract-supplemented group, ex vivo copper-initiat ed oxidation of LDL (lag phase, mean +/- SD) was 40 +/- 11 min at the basel ine, and increased significantly to 47 +/- 6 min [P <0.05 compared with pla cebo (38 +/- 4 min) and the washout values (40 +/- 5 min)]. In the querceti n-supplemented group, the lag phase was 44 +/- 11 and 40 +/- 5 min for the baseline and placebo, respectively, and increased significantly to 51 +/- 7 min [P <0.05 compared with placebo and washout (41 +/- 9 min)] after suppl ementation. Plasma lipids (triglycerides, total cholesterol, LDL- and HDL-c holesterol) did not change during the study period. Supplementation with re d wine extract or quercetin had no effect on plasma vitamin C and E, retino l, and carotenoid concentrations. Conclusions: Alcohol-free red wine extract and one of its components, querc etin, can inhibit LDL oxidation after in vivo supplementation; such "inhibi tion" is unrelated to changes in antioxidant vitamin and carotenoid concent rations. (C) 2000 American Association for Clinical Chemistry.