Effect of Physiological Concentrations of Vitamin C on the Inhibitation of Hydroxyl Radical Induced Light Emission from Fe(2+)-EGTA-H(2)O(2) and Fe(3+)-EGTA-H(2)O(2) Systems In Vitro

Ascorbic acid (AA) has antioxidant properties. However, in the presence of Fe(2+)/Fe(3+) ions and H(2)O(2), it may behave as a pro-oxidant by accelerating and enhancing the formation of hydroxyl radicals ((•)OH). Therefore, in this study we evaluated the effect of AA at concentrations of 1 to 200 µmol/L on (•)OH-induced light emission (at a pH of 7.4 and temperature of 37 °C) from 92.6 µmol/L Fe(2+)—185.2 µmol/L EGTA (ethylene glycol-bis (β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid)—2.6 mmol/L H(2)O(2), and 92.6 µmol/L Fe(3+)—185.2 µmol/L EGTA—2.6 mmol/L H(2)O(2) systems. Dehydroascorbic acid (DHAA) at the same range of concentrations served as the reference compound. Light emission was measured with multitube luminometer (AutoLumat Plus LB 953) for 120 s after automatic injection of H(2)O(2). AA at concentrations of 1 to 50 µmol/L and of 1 to 75 µmol/L completely inhibited light emission from Fe(2+)-EGTA-H(2)O(2) and Fe(3+)-EGTA-H(2)O(2), respectively. Concentrations of 100 and 200 µmol/L did not affect chemiluminescence of Fe(3+)-EGTA-H(2)O(2) but tended to increase light emission from Fe(2+)-EGTA-H(2)O(2). DHAA at concentrations of 1 to 100 µmol/L had no effect on chemiluminescence of both systems. These results indicate that AA at physiological concentrations exhibits strong antioxidant activity in the presence of chelated iron and H(2)O(2).