Analysis of saliva for glutathione and metabolically related thiols by liquid chromatography with ultraviolet detection

Summary. A method for simultaneous determination of glutathione and its precursors cysteine, cysteinylglycine and homocysteine in saliva is presented. The procedure involves reductive conversion of disulfides to thiols, derivatization to their 2-S-quinolinium derivatives with 2-chloro-1-methylquinolinium tetrafluoroborate and separation and quantitation by reversed-phase ion-pairing high performance liquid chromatography with ultraviolet detection at 355 nm. The calibration performed with saliva samples spiked with thiol disulfides, within the practical concentration ranges, showed linear response of the detector. The method applied to the saliva samples donated by volunteers showed mean concentration (SD, n = 8) of cysteine, cysteinylglycine, glutathione and homocysteine: 26.5 (31.6), 6.05 (5.12), 16.97 (7.68), 3.64 (1.34) nmol/ml respectively.