(5) Glutathione
Glutathione (GSH) is a tripeptide. It contains an unusual peptide linkage between the amine group of cysteine and the carboxyl group of the glutamate side chain. Glutathione, an antioxidant, helps protect cells from reactive oxygen species such as free radicals and peroxides. The most widely used method for the determination of glutathione in biological samples is that developed by Ellman i. e. 5-5’ dithiobis (2- nitrobenzoic acid), which reacts with sulfydryl compounds to give a relatively stable yellow color. This compound is water soluble which has made it possible to develop a very accurate method of GSH determination, in which the color formed is related to the amount of glutathione [29, 35].