Fig. 4. Non-enzymatic reaction between 1.2 mM HEDS and 1.2 mM GSH. (A) The time-dependent formation of 2-ME and consumption of HEDS were analyzed by HPLC. Calibration of the 2-ME signal and subsequent regression analysis of the obtained concentrations over time revealed that approx. 70% of the substrate was converted to product at equilibrium. A concentration of 0.6 mM 2-ME was reached after 22 min. (B) The time-dependent consumption of GSH and formation of GSSEtOH and GSSG were analyzed by mass spectrometry. Semi-quantitative analysis of the GSH peak areas revealed a consumption of approx. 65% of substrate at equilibrium.