Meso-tetra-p-tolylporphyrin: synthesis, characterisation, antioxidant activity and determination of binding parameters of with superoxide anion radical

Abstract

In this paper we present the synthesis and the evaluation of the antioxidant activity of meso-tetra-p-tolylporphyrin (TPPH₂(p-methyl)) using superoxide anion radical (O^-₂) in DMF as a solvant. The binding parameters of the interaction between the synthesised compound and the radical (O^-₂) were also measured using cyclic voltammetry techniques. TPPH₂(p-methyl) shows lower antioxidant activity (30.7 ± 0.08 mg/mL) than that of α-tocopherol standard (3.04 ± 0.03 mg/mL). The value of the binding Gibbs energy of -8.15 KJ.mol^-1 calculated for TPPH₂(p-methyl) suggests an electrostatic interaction of (O^-₂) with TPPH₂(p-methyl) which has been found to be the dominant interaction mode. The kinetics of the interaction reaction was also measured having second-order rate constant values equal to 0.2 M^-1 s^-1.