期刊
ELECTROCHIMICA ACTA
卷 56, 期 21, 页码 7421-7427出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.electacta.2011.04.121
关键词
Cyclic voltammetry; Electron transfer; Flavonoids; Oxidation products; Spectroelectrochemistry
资金
- Grant Agency of the Czech Republic (GACR) [203/09/1607, 203/08/1157]
- Ministry of Education of the Czech Republic [COST OC140]
The knowledge of the degradation pathways of natural dyes used in medieval textiles is necessary for the restoration of their original color. Quercetin, one of such colorants, reportedly yields the wide spectrum of oxidation products in different types of media. This study deals with electrochemical oxidation mechanism of quercetin in nonaqueous solution, which has not been yet attempted. The final oxidation product at the first oxidation wave was identified by HPLC-DAD and GC-MS techniques as 2-(3',4'-dihydroxybenzoyl)-2,4,6-trihydroxybenzofuran-3(2H)-one. The apparent two-electron process at the potential of the first oxidation wave yields current-voltage shapes with one-electron characteristics. The in situ spectroelectrochemistry measurements proved the oxidation mechanism leading through a short-lived anion radical. Two possibilities of the oxidation mechanism are discussed: two one-electron transfers, which do not have identical but similar redox potentials. or the presence of a disproportionation chemical reaction following the first one electron transfer. The quinone formed in either case is stable only on the time scale of a fast spectroelectrochemistry and undergoes fast hydroxylation reaction, where 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxybenzofuran-3-one is formed. This compound is oxidized at the potential of the second oxidation wave of quercetin. (C) 2011 Published by Elsevier Ltd.
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