Representative kinetic traces of guaiacol (9 mM) oxidation by H2O2 (0.9 mM) mediated by LPO (5 μM) previously incubated in the absence (Trace A) or in the presence of 5 mM GSH (Trace B) for 2 h at 37 °C. After that, the incubations were diluted 10,000 times in the spectrophotometer cuvette containing phosphate buffer, guaiacol and finally H2O2 were then added. Experiments were performed in triplicate. For traces C–E fresh LPO was used. For these experiments GSH at the concentrations indicated was added prior to H2O2. Trace C, GSH 2.5 μM was added; Trace D, GSH 12.5 μM was added; Trace E, GSH 50 μM was added.