Effect of Physiological Concentrations of Vitamin C on the Inhibitation of Hydroxyl Radical Induced Light Emission from Fe-EGTA-HO and Fe-EGTA-HO Systems In Vitro.

Ascorbic acid (AA) has antioxidant properties. However, in the presence of Fe/Fe ions and HO, 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-185.2 µmol/L EGTA (ethylene glycol-bis (β-aminoethyl ether)-N,N,N',N'-tetraacetic acid)-2.6 mmol/L HO, and 92.6 µmol/L Fe-185.2 µmol/L EGTA-2.6 mmol/L HO 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 HO. AA at concentrations of 1 to 50 µmol/L and of 1 to 75 µmol/L completely inhibited light emission from Fe-EGTA-HO and Fe-EGTA-HO, respectively. Concentrations of 100 and 200 µmol/L did not affect chemiluminescence of Fe-EGTA-HO but tended to increase light emission from Fe-EGTA-HO. 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 HO.