Amperometric and Potentiometric Determination of Catechin as Model of Polyphenols in Wines

Catechin antioxidant action at various pH studied by cyclic voltammetry and PM3 semi-empirical calculations

“…A linear decrease in the formal oxidation potential of the first voltammetric peak by À59 mV/pH (E 0 0 ðmVÞ ¼ 602.42 À 59.27 Â pH, r 2 = 0.998) has been observed on both activated and non-activated electrodes and is consistent with the literature data [4,5].…”

“…A possibility is that at higher potentials less oxidizable -OH groups of a single molecule species may become oxidized. In the case of catechin and epicatechin, this peak is thought to correspond to the oxidation of the meta-diphenol groups on the A-ring [5,15]. Also, the occurrence of the chemical reactions subsequent to the one-electron or two-electron oxidation may introduce new oxidizable species into the solution [26,27].…”

“…The catechin molecule is a representative monomer found in many polyphenols and understanding its conformational preferences and flexibility has been an important mission of many researchers [5,36]. The current view of the pyrane ring conformation in compounds like these is of a conformer ensemble with distributed structures and the catechol ring in a pseudoequatorial (E-conformer) or pseudoaxial (A-conformer) position.…”

“…Flavanoids are present in body cells and fluids as a result of ingestion of fruits, vegetables, and plant-derived food and beverages, such as wine, tea and chocolate. Application of (+)-catechin as a phenolic standard in quantitation of reducing equivalents in food and biological fluids and its oxidation mechanism are therefore of particular interest [2][3][4][5][6][7][8][9]. One of the most recent methods used to measure antioxidant activity of phenolic compounds is selective electro-oxidation by cyclic voltammetry [10][11][12][13][14][15][16][17][18].…”

Electrochemical behaviour of N-acetyl-l-cysteine on gold electrode—A tentative reaction mechanism

“…Electrochemistry represents a welldefined methodology to study redox properties of antioxidant species, in model solution as well as in complex media. Previous works performed in the laboratory have shown possibilities to evaluate the antioxidant capacity of various media such as wine [15], skin [16], or dermocosmetic creams [17], by simple electrochemical measurements. Furthermore it has also been possible to determine and sometimes quantify the major redox markers involved without any pre-treatment of the sample.…”