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.