2.2.4. Polyphenol Oxidase (PPO) and Peroxidase (POD) Activity Levels

The antioxidant effect of PD on the inhibition of enzymes activity levels was determined using the pericarps of 15 fruit samples. Crude enzyme extract was obtained according to the method used by Khan et al. [7] and Duan et al. [22]. The reaction mixture used to assess the PPO activity was prepared by following the protocol used by Khan et al. [7] and Jiang [23]. Absorbance was recorded at 410 nm for 5 min with a UV–visible spectrophotometer (SPECORD 50 Plus, Analytik Jena, Germany). One unit of enzyme activity was defined as the activity that caused a change of 0.001 in the absorbance per min. The reaction mixture for POD activity was prepared following the protocol used by Khan et al. [7] and Zhang et al. [24] and absorbance was measured using a UV–visible spectrophotometer (SPECORD 50 Plus, Analytik Jena, Germany). One unit of enzyme activity was defined as the amount that caused a change of 0.01 in the absorbance per min. Protein contents were determined according to the method used in [25]. Enzyme (PPO and POD) activity levels were expressed as units min−<sup>1</sup> mg−<sup>1</sup> protein. The experiments were performed in triplicate.
