Electrochemical investigations of antioxidant interactions with radical anion and dianion of 1,3-dinitrobenzene

Interactions of five antioxidants(AO), quercetin (Q), morin (M), rutin(R), ascorbic acid (AA) and beta-carotene (beta-C) with anion radical and dianion of 1,3-dinitrobenzene (1,3-DNB) in two aprotic solvents - dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) - have been studied by cyclic voltammetry using glassy carbon electrode. Electrochemical parameters - peak potential (E-p), half-wave potential (E-1/2), and peak current (i(p)) - for the reduction of 1,3-DNB before and after the addition of various concentrations of antioxidants, were evaluated. A gradual decrease in the oxidation peak current and finally irreversibility in 1,3-DNB radical anion and dianion systems upon the addition of antioxidant, reveals their interactions. The homogeneous bi-molecular rate constant (k(2)) Was determined from electrochemical data. In comparison to all other antioxidants used, enhanced homogeneous second order rate constant for the interaction of morin with 1,3-DNB anion radical and dianion, was observed. This aspect is attributable to protonation initiated by hydrogen bonding and greater acidic nature of morin. (C) 2009 Elsevier Ltd. All rights reserved.