Surface electrochemical oxidation and polymerization mechanism of epicatechin

Document Type

Article

Publication Date

2-15-2013

Abstract

Electrochemical process of epicatechin, one of the flavonoids antioxidants, was studied here by cyclic voltammetry and semiempirical molecular orbital computation (MOPAC). Electrochemical oxidation of epicatechin showed a multistep mechanism with two anodic peaks being recognized at about +0.14 V and +0.52 V (vs. Ag/AgCl). The first peak is strong concentration dependent, showing an adsorptive feature between 1 × 10-8 M and 2 × 10 -7 M, a diffusion controlled feature between 2 × 10 -7 M and 1 × 10-5 M, and a surface polymerization feature between 1 × 10-5 M and 1 × 10-3 M. Computation showed that the first electron was released at 4?-hydroxyl group in B-ring. No charge delocalization occurs between A- and B-rings. Higher pH medium favors oxidation. The oxidation rate is faster in strong acidic or basic medium and slower in a weak acidic medium. This research may help to explain the complexity of antioxidant activity of flavonoids and as a complement method to characterize the role of flavonoids antioxidants in treating oxidative stress diseases.

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