The change in absorbance was measured using an UV–vis spectrophotometer Hewlett–Packard mod. 8453, at a wavelength of 414 nm. The reaction was made mixing 1.5 mM ABTS, 1.18 mM H2O2 and 0.25 μM HRP in a glycin–HCl 50 mM (pH 4.5) buffer in a total volume of 2 mL.