Quantification of reduced and oxidized glutathione in wine by MALDI-TOF MS

Reduced glutathione (GSH) is one of the important antioxidants in the winemaking and aging process and it also regulates the color and flavor of wines. Accurate and rapid quantification of GSH is crucial in wine quality control. In this study, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was demonstrated to quantify GSH and oxidized glutathione (GSSG) of wine in a high-throughput way. Quinoline-5,8-dione was used as a label to react with GSH, and the derivative of GSH, glutamate-cysteine-alanine, acted as the internal standard (IS). The quantitative decrease of GSH and the increase in GSSG were detected with a relative standard deviation of <= 5%, after the wines were exposed to air from one to seven days, and the concentration changes of GSH and GSSG were measured by simple dilution. All the results suggested the feasibility and potential of this method for wider applications in the quantification of GSH and GSSG.