Peroxidase (POD) activity was determined by measuring the increase in absorption at 470nm according to Kalir et al.
Xiaona ZHANG et al. with modification. The reaction was carried out at 25oC for 20min in a 3mL reaction mixture containing 0.02 mL tissue extract, 50 mmol/L sodium phosphate buffer (pH 7.0), and guaiacol 20 mmol/L. The reaction was initiated by the addition of 20 μL H2O2.One unit of POD was defined as the amount of enzyme that caused a 1.0 increase of A470 per min under the assay condition. Each experiment was repeated three times.