Measurement of total antioxidant activity with chlorpromazine radical cation.

Unlabelled: In the present study there is described a simple and sensitive method for the evaluation of antioxidant activity in chlorpromazine-Fe (III) system using ascorbic acid as standard.

Material And Method: Chlorpromazine [2-chloro-N-(3-dimethyl-aminopropyl)-phenothiazine] is oxidized in acidic media by Fe (III) with the formation of a stable radical cation characterized by an intense visible absorbtion band (lambda = 540 nm). The optimum parameters for the stability of the radical cation have been studied: molar ratio chlorpromazine-Fe (III), pH, solvents. Spectrophotometric methods have been used in these studies.

Results: The chlorpromazine radical cation is stable in the acidic media (pH = 3) at a molar ratio chlorpromazine: Fe (III) of 2: 1. Ascorbic acid reduces these radicals and induces a decrease of absorbance. Percent inhibition was calculated and plotted as a function of the concentration of standard antioxidant solutions. The results show that percent inhibition varies in a linear manner with the ascorbic acid concentration. Percent inhibition is higher when the antioxidant solution is added after generation of radical cation.

Conclusions: It has been developed a method for evaluating antioxidant activity in the chlorpromazine: Fe (III) system using ascorbic acid as a standard. The method is fast, simple and sensitive; it can be applied for the detection and evaluation of the antioxidant activity of simple or complex systems.