Study of Antithyroid and Antioxidant Properties of Cysteine, Glutathione, and Methionine by Spectrophotometry and High Performance Liquid Chromatography

Abstract

The antithyroid properties of sulfur-containing amino acids cysteine and methionine and glutathione tripeptide are studied by evaluating the kinetic and thermodynamic parameters of analyte interaction anionic iodine complexes ( $${\text{I}}_{{\text{3}}}^{ - }$$ and I2Cl–).The rate constant of the second-order reaction between cysteine and triiodide is the maximum rate constant, comparable to the rate constants of physiological processes. The antioxidant activity of cysteine and glutathione is estimated by the kinetic method with the spectrophotometric control of the reaction rate using the second-order reaction rate constant with the chromogen radical 2,2'-diphenyl-1-picrylhydrazyl (DPPH) and the reaction half-life in alcoholic media. The antioxidant properties of cysteine and glutathione, manifested in the reaction with DPPH, were used to develop a simple and sensitive method for their quantitative determination using a pseudo-first-order rate constant. The study of the reaction of analytes with a chromogen radical made it possible to evaluate their antiradical activity by spectrophotometry analysis, supplemented with HPLC.