Glutathione (GSH) is an important antioxidant molecule that functions as a cofactor for a variety of enzymes and is involved in various biological processes. A variation in glutathione levels is an indicator of oxidative stress. The SensoLyte® Glutathione Cellular Assay Kit utilizes an optimized enzymatic method for determination of the glutathione levels in cell or tissue extracts. The substrate provided in the kit can selectively react with GSH in the reaction catalyzed by glutathione S-transferase (GST) and form a fluorescent glutathione adduct. The resulting blue fluorescence can be monitored at excitation /emission= 390 nm/480 nm. The assay has a linear range of 0-100 µM of GSH. This kit does not require the usage of deproteination for biological samples.