Comparison of analytical methods for quality control of pharmaceutical formulations containing glutathione

Sensitive and selective determination of glutathione in probiotic bacteria by capillary electrophoresis–laser induced fluorescence

Glutathione (GSH) is a thiol with an important function in protecting tissue against the oxidative stress which has been related to carcinogenesis in the colon. For this reason the development of probiotic species producing glutathione could be of great interest. To determine the glutathione content of some probiotic bacteria of the Bifidobacterium and Lactococcus genera, a very sensitive and selective analytical method based on capillary electrophoresis coupled to laser-induced fluorescence detection has been developed. Pretreatment of cell-lysate samples is very simple--precipitation of protein with acetonitrile in 1:2 volume ratio. The fluorophore 5-iodoacetamidofluorescein (5-IAF) was chosen for glutathione derivatisation; it reacts with thiols at pH 12.5, forming a fluorescent adduct which is excited by a laser at 488 nm for detection. The reaction conditions optimised were temperature, time, and 5-IAF/GSH molar ratio. Electrophoresis was performed with a carbonate buffer (25 mmol L(-1), pH 9.8) as background electrolyte and a voltage of 30 kV; an electrophoretic run was complete in less than 7 min. There was a good linear relationship between concentration and response in the range 2.5-500 ng mL(-1) and the LOD was 0.5 ng mL(-1). The glutathione content of probiotic cells was determined by using the standard additions method to reduce matrix effects. The method was fully validated and shown to be of suitable sensitivity and selectivity for determination of GSH in probiotic cell lysates.

Analytical methods to investigate glutathione and related compounds in biological and pathological processes

Reduced glutathione (GSH, gamma-L-glutamyl-L-cysteinylglycine) is a fundamental low-molecular mass antioxidant that serves several biological functions. Upon enzymatic and non-enzymatic oxidation, GSH forms glutathione disulfide (GSSG) and, under particular conditions, may generate other oxidative products. The determination of GSH, its precursors, and metabolites in several bio-matrices is a useful tool in studying oxidative stress. Many separative and non-separative methods have been developed and improved for the assay of GSH and related compounds. At present, high-performance liquid chromatography and capillary electrophoresis are the most used separative techniques to determine GSH and congeners. The review will deal with analytical methods developed over the last few years for the determination of GSH and related compounds, and with the procedures performed in sample pre-treatment in order to minimize analytical errors. Since GSH, GSSG, and related compounds lack of strong chromophores or fluorophores, it is advantageous, in many assays, to derivatize the compounds in order to improve the detection limit with UV-Vis and to allow fluorescence, thus the most commonly used labeling agents are also described.