Electrochemistry of catechol-containing flavonoids.

The electrochemical properties of four structurally related flavonoids, quercetin, quercetin-3-O-rhamnose (quercitrin), quercetin-3-O-rutinose (rutin) and luteolin were investigated. These flavonoids were shown to undergo homogenous chemical reactions following oxidation at a glassy carbon electrode. These reactions were studied using cyclic voltammetry and rotating ring-disk voltammetry. Both first-order and zero-order processes were observed. The rate of the zero-order process was strongly dependent on the substituent at the C-3 position of the flavonoid. The rate of the first-order process was independent of substitution. Two products were observed using liquid chromatography. These products did not correspond to previously reported products of enzymatic oxidation. The products were not stable under conditions for isolation.