Original Scientific Article Electrochemical and Antioxidant Properties of

Abstract. The electrochemical properties of three structurally different flavonoids ((+)-catechin, quercetin and rutin) on a glassy carbon electrode were studied at different pH by cyclic, differential pulse and square-wave voltammetry. It was determined that in all investigated compounds oxidation of catechol 3',4'-dihydroxy group on the B-ring (the first oxidation peak) occurs. This process is reversible, pH de-pendent and includes the transfer of 2e − and 2H+. The products of electrochemical oxidation of all investi-gated flavonoids (especially of quercetin) strongly adsorb on the electrode surface. In terms of quantifica-tion, the absorbance value, proportional to the remaining ABTS+ • concentration, is measured after a fixed reaction time. Results are expressed as Trolox equivalents (TEAC value), that is, as the concentration of Trolox solution (mmol dm−3) with an antioxidant capacity equivalent to that found for 1.0 mmol dm−3 of the substance under investigation. It was found that the TEAC values depend on the concentration of the investigated compounds. The activity sequence of the investigated, structurally different, flavonoids fol-lows the sequence: quercetin> (+)-catechin> rutin