Simultaneous quantification of glutathione, glutathione disulfide and glutathione-S-sulfonate in grape and wine using LC-MS/MS

A fast, sensitive and reproducible method using LC-MS/MS for simultaneous quantification of glutathione (GSH), glutathione disulfide (GSSG) and glutathione-S-sulfonate (GSSO₃H) was developed, optimised and applied in analysis of grape juice and wine samples. The results show that only GSH (10-60 mg·L^-1) and GSSG (2-11 mg·L^-1) are found in grape juice when SO₂ is not added. GSSO₃H was detected in must samples treated with SO₂ but only at a low concentration (<1 mg L^-1). In the wine samples, the dominant form of glutathione was GSSO₃H (5-11 mg L^-1), followed by GSH (0-5 mg L^-1) and GSSG (0-6 mg L^-1), underscoring the importance of GSSO₃H quantification. GSSO₃H formation in wine was correlated with the total SO₂ level in the wine. We believe this is the first report on GSSO₃H quantification in wine.