Evaluation of free radical scavenging activity of some antioxidants.

UNLABELLED Measurement of free radical scavenging capacity of antioxidants is influenced by a number of parameters that depend on reaction rate. AIM A new method for assessing the free radical scavenging activity in which the influence of antioxidant concentration and reaction rate on chlorpromazine radical cation absorbance are simultaneously monitored. MATERIALS AND METHODS The change in radical solution absorbance at 525 nm within a fixed time at different concentrations of the standard antioxidant--ascorbic acid (AA) are determined and percent inhibition is calculated. RESULTS The percent inhibition of color was plotted versus time, and the area under the curve was calculated for each concentration of the standard antioxidant. The calibration curve was obtained by plotting the area under the curve versus ascorbic acid concentration. The antioxidant activity of the samples was calculated using the regression line equation (r2 = 0.9991) and expressed as ascorbic acid molar equivalents (AAE) depending on the unit of measurement chosen for the tested product. CONCLUSIONS The proposed method takes into account the two parameters influencing the kinetics of the reaction between antioxidant and radicals, namely the antioxidant concentration and fixed time for measuring absorbance.