Antioxidant and Radical Scavenging Activities of Uric Acid

Abstract

Uric acid is the important plasma antioxidant that can protect cells from damage by reactive oxygen species. It is the major nitrogenous compound in urine, but it is also found in other biological fluids such as serum, blood and saliva. The aim of this research was to examine the antioxidant and radical scavenging activities of uric acid. Several mechanisms of potential antioxidant and radical scavenging activities of uric acid including 2,2-azino-bis(3-ethylbenzthiazoline- 6-sulfonic acid) (ABTS) radical scavenging, 1,1-diphenyl-2- picryl-hydrazyl free radical (DPPH^•) scavenging, total antioxidant activity, reducing activity, hydrogen peroxide (H₂O₂) scavenging and metal chelating activitiy on Fe²⁺ ions were examined as in vitro assays. Total antioxidant activity was measured according to ferric thiocyanate method. α-Tocopherol and trolox, a water-soluble analogue of tocopherol, were used as the reference antioxidant compounds. Uric acid neutralized the activities of radicals and inhibited the peroxidation reactions of linoleic acid emulsion. Uric acid showed 67.7 % inhibition on lipid peroxidation of linoleic acid emulsion, at the 20 μg/mL concentration. However, α-tocopherol and trolox exhibited 54.7 and 20.1 % inhibition on peroxidation of linoleic acid emulsion, respectively, at the above mentioned concentration. Uric acid had also effective DPPH^•, ABTS^•+ scavenging, H₂O₂ scavenging, total reducing power and metal chelating on Fe²⁺ ions activities.