Cathodic reduction of coenzyme Q10 on glassy carbon electrode in acetic acid-acetonitrile solutions

The electrochemical reduction of coenzyme CoQ(10) and CoQ(0) on glassy carbon (GC) has been investigated in mixed solvent containing 80 vol.% acetic acid and 20 vol.% acetonitrile. A combination of cyclic voltammetry (CV) and rotating disk electrode technique (RDE) was employed to elucidate the mechanism of electrode processes. The results obtained were interpreted in terms of an E(r)E(q) mechanism involving the inverted ordering of formal potentials, i.e. E(2)(0')>E(1)(0'). The cathodic processes of both compounds consist of two successive one-electron one-proton steps, whereas the second electron transfer is thermodynamically more facile than the first. The processes occur with the generation of unstable semiquinone radicals as primary products. The results presented can help in explanation of the biochemical properties of CoQ(10) in the living cell.