Repeated red wine consumption and changes on plasma antioxidant capacity and endogenous antioxidants (uric acid and protein thiol groups)

This study aims to ascertain the in vivo antioxidant properties of red wine by determining how it affects antioxidant biomarkers (plasma antioxidant capacity (PAC) and endogenous antioxidants such as uric acid or protein thiol groups). Antioxidant biomarkers have been assessed in eight healthy human volunteers after repeated intakes of 300 mL of red wine every day for a week. During this intervention period, volunteers followed a low phenolic diet designed to prevent the phenolic compounds in wine from interfering with the phenolics from other foods or beverages. This diet was followed throughout the week that the volunteers drank wine and for another control week when they drank water. Biomarkers were determined before the subjects taking part in the study started the intervention period with red wine (Monastrell variety) and 1, 3, and 7 days after. PAC was evaluated by the Ferric Reducing Ability of Plasma assay (FRAP), and the Oxygen Radical Absorbance Capacity assay using fluorescein (ORAC-FL). In addition, the concentrations of endogenous antioxidants such as uric acid, albumin, bilirubin, and protein thiol groups were analyzed. The FRAP method shows that PAC increased after the week of wine consumption but decreased after the week without wine consumption. The uric acid concentration did not show any changes that were significantly different from our results in acute wine intake studies. Protein thiol groups decreased significantly (p < 0.05) with the low phenolic diet, but this decrease was not statistically significant if the diet was taken with red wine (p < 0.05).