Electrochemical Bechaviour of Some Chlorogenic Acids and Their Characterization in Coffee by Square-Wave Voltammetry

Abstract

The electrochemical behaviour of six chlorogenic acids (CGAs) isomers: three caffeoylquinic acids, CQAs (5-CQA, 4-CQA, 3-CQA) and three dicaffeoylquinic acids, diCQAs (3,4-diCQA, 3,5-diCQA, 4,5-CQA) was studied by SWV and compared with the electrochemical behaviour of caffeic acid (CFA), precursor of investigated CGAs. The study reveals that electrochemical behaviour of investigated CGAs strongly dependent on their chemical structure and electronic properties, particularly on electron-donating effect of –OH and –CH=CH- groups, and a strong electronwithdrawing effect of ester (-COOR) group presented in their structure. SWV measurements show that electrochemical oxidation/reduction of CGAs at GCE is reversible, pH-dependent, two electron-two proton process. The oxidation/reduction processes occurred on the catechol moiety (ortho-dihydroxyl groups) in the structure of CGAs molecules. The oxidation product(s) relatively strongly

 3,5-diCQA (isochlorogenic acid A), 3,4-diCQA (isochlorogenic acid B) and 4,5-diCQA (isochlorogenic acid C)were obtained from Chengdu Biopurify Phytochemicals Ltd. (Chengdu Sichuan, China).