2.9.1. Enzymatic antioxidants
Superoxide dismutase (SOD; EC 1.15.1.1) activity in each sample was monitored spectrophotometrically by measuring the formation of purple formazan compound formed due to photoreduction of NBT at 560nm, using the method of Giannopolitis and Reis (1977). One unit (U) of SOD activity is the amount of enzyme necessary to inhibit (50%) the NBT reduction.
Peroxidase (POD, EC 1.11.1.7) activity in each sample was determined spectrophotometrically by measuring the increase in absorbance due to pyrogallol oxidation at 430 nm using the extinction coefficient of 25.5 mM−1 cm−1, as suggested by Gahagan et al. (1968). One unit (U) of POD activity is 1 nmol pyrogallol oxidized min−1.
Catalase (CAT; EC 1.11.3.6) activity in each sample was monitored spectrophotometrically by measuring the decrease in absorbance due to H2O2 dissociation at 240 nm using the extinction coefficient of 39.4 mM−1cm−1, as suggested by Aebi (1984). One unit (U) of CAT activity is 1 nmol H2O2 dissociated min−1.
Likewise, glutathione-S -transferase (GST, EC 2.5.1.18) activity in each sample was monitored spectrophotometrically by measuring the increase in absorbance due to conjugate formation between GSH and CDNB at 340 nm using the extinction coefficient of 39.4 mM−1 cm−1, as suggested by Habig et al. (1974). One unit (U) of GST activity is 1 nmol CDNB-conjugates formed min−1.