Abstract
The redox behaviour of a potential anticancer organic compound, 5,8-dihydroxynaphthalene-1,4-dione (DND), was investigated in 1 : 1 buffered aqueous ethanol using cyclic, differential pulse, and square wave voltammetry. The redox processes were found to occur in a pH-dependent diffusion-controlled manner. Presence of an alpha-hydroxyl group stabilised semiquinone radical of DND, formed by the gain of 1 e(-) and 1 H+, prevented the second step reduction, which is in contrast to the general mechanism previously reported for quinines in protic and aprotic media. In addition, our results supported an independent oxidation and reduction process. Square wave voltammetry provided evidence about the reversible and quasi-reversible nature of oxidation and reduction peaks. Based on the voltammetric results, the electrode reaction mechanism of DND was proposed. Parameters including pK(a), transfer coefficient, diffusion coefficient, and electron transfer rate constant were evaluated. The values of pK(a) obtained from cyclic voltammetry and ultraviolet-visible spectroscopy not only agreed with each other, but also with reported values of structurally related compounds evaluated by other techniques.