Quercetin supplementation decreases erythrocytes oxidative damage at resting and after an acute bout of eccentric exercise in humans

Quercetin (Q) functions as antioxidant in vitro, but its effect have been minimally examined in combination with exercise in humans. The purpose of this investigation was to determine the effects of a diet supplemented with 1 g per day of Q for 2 weeks on the erythrocytes oxidative balance before and after an acute bout of eccentric exercise (EE). Fourteen volunteer males were randomly assigned, in a double-blind crossover design, to a placebo or experimental supplemented groups. Blood samples were taken before and after 2 weeks of supplementation under resting and post-exercise conditions. Erythrocytes glutathione (GSH, GSSG, GSH/GSSG), malonaldehyde (TBARs), enzymes antioxidant activities as well as time of hemolysis were evaluated in ex vivo. Quercertin per se did not affect redox homeostasis but increased the time of hemolysis and decreased TBARs levels. Following the EE the Q group displayed a higher GSH/GSSG ratio and a less pronounced increase in TBARs, compared to placebo group. Moreover, we found that GPx enzyme activity were induced after EE only in Q group, while any significant modification of this parameter was detected in placebo group. In conclusion, the Q supplementation may be used as a countermeasure against oxidative stress inducing, in erythrocytes, a cellular adaptation allowing subjects to better cope with the oxidative stress induced by an acute exercise