Antioxidation Mechanisms of Uric Acid

Article abstract of DOI:10.1021/ja00197a042

One-electron oxidation of uric acid generates the urate radical, which was studied in aqueous solution by pulse radiolysis and oxygen-uptake measurements.Acid-base properties of the uric acid radical were determined, i.e., pK_a1 = 3.1 +/- 0.1 and pK_a2 = 9.5 +/- 0.1.The reaction of the radical with oxygen was too slow to be measured, k < 1E-2 dm³ mol^-1 s^-1.The one-electron-redox potential vs NHE, E₇ = 0.59 V, was derived from the pH dependence of the redox potential, which was fitted trough the values measured at pH 7 and 8.9 and those previously at pH 13.Rapid reactions of uric acid with oxidizing species and peroxy radicals were indicative of uric acid as a possible water-soluble physiological antioxidant.Rapid reaction of uric acid with the guanyl radical indicates that uric acid may also act as a repair agent of oxidative damage to DNA bases.