Antioxidant capacity of plasma after red wine intake in human volunteers

Plasma antioxidant capacity (AC) has been assessed in eight healthy human volunteers after wine intake. Analytical methods used for evaluating AC included the ferric reducing ability of plasma (FRAP) and oxygen radical absorbance capacity using two different fluorescent probes, P-phycoerythrin (ORAC-PE) and fluorescein (ORAC-FL). In addition, the concentrations of endogenous antioxidants such as uric acid, albumin, and bilirubin were determined. The suitability of analytical methods was evaluated with two different biological matrixes: plasma and serum. Plasma AC was determined before ingestion of 300 mL of red wine (baseline value) and 30, 55, and 120 min afterward. Maximum average increase in AC values was reached at 55 min. Plasma AC determined by ORAC-PE at time zero was significantly correlated with albumin concentration. Plasma AC determined with FRAP at time zero is well correlated with uric acid. Moreover, a good linear correlation was found between uric acid concentration and AC determined by FRAP in each volunteer. The maximum concentration of uric acid occurred after 55 min. Uric acid increase accounts for a nonnegligible part in FRAP values and must be evaluated when using this method for assessing AC in plasma.