Estimation of the Antioxidative Properties of Amino Acids - an Electrochemical Approach

The study antioxidant properties of amino acids is very important, because they are the building blocks of peptides and proteins, and they take part in many fundamental biochemical processes. Electrochemical methods provide big opportunities for investigation and assessment of antioxidant capacity of these compounds. The electrooxidation of cysteine, cystine, phenylalanine and alanine was investigated in a non-aqueous solution at a platinum electrode. The process of oxidation and its kinetics was investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The electrochemical oxidation of amino acids is an irreversible process that proceeds in two steps. Thus, this study demonstrated that cyclic voltammetry in aprotic solvents is a very useful technique for studying the reactivity of such compounds and their antioxidant activities due to the high sensitivity of the technique. Quantum chemical calculations were also performed for the amino acids. The molecular geometries of the amino acids in the gas phase were studied using ab initio quantum chemical calculations with the restricted Hartree-Fock (RHF). Structural investigations of the amino acids were conducted using FTIR. Mechanisms for the oxidation of cysteine and phenylalanine were then proposed.