Glutathione (GSH), a tripeptide antioxidant, plays multiple biological functions. It is involved in detoxification of harmful molecules, such as reactive oxygen species (i.e., hydrogen peroxide and hydroperoxides) through glutathione peroxidases, and xenobiotics through glutathione transferase. It is also involved in signal transduction, gene expression, apoptosis and interaction with nitric oxide. Glutathione antioxidant status is frequently measured in physiology and pathophysiology.

Assay principal: GSH reacts with Ellman’s reagent (5,5’-dithiobis(nitrobenzoic acid) or DTNB) to produce a chromophore TNB with maximal absorbance at 412 nm and oxidized glutathione GSSG. Tietze formulated an enzymatic method to regenerate GSH using Glutathione Reductase and NADPH, to provide specificity and improved sensitivity for the assay. The reaction mechanism is depicted schematically in the following figure. Since glutathione reductase is used, the amount of glutathione measured represents the sum of reduced and oxidized glutathione in the sample ([GSH]t = [GSH] + 2 x [GSSG]). The rate of absorbance change (DA412nm/min) is made to be linear for the convenience and consistence of measurement, and is linearly proportional to the total concentration of GSH. The concentration of an unknown (sample) is determined by calculating from the linear equation generated from several standards of glutathione.

• Formulated for convenient and fast assay for biological samples — 3 minutes/assay at room temperature.
• Use simple spectrophotometers or microtitre plate readers.
• No interference from cysteine and metal ions.
• Wide assay range from 0.1 µM to 30 µM in sample (dilution is required for samples with higher GSH concentration.)
• Kit includes all required reagents and standards.