2.6. Spectrophotometric determination of antioxidant activity
The popular method employing ABTS radical was employed
for the colorimetric determination of antioxidant activity as
described earlier (Kusznierewicz, Piasek, Bartoszek, & Namiesnik,
2011). The solution of ABTS reagent (7 mmol/L in 2.45 mmol/L
Na2SO4) was prepared a day before measurements. Just before use,
ABTS solution was diluted with methanol to adjust the level of
the final solution absorbance to 0.7 at 734 nm. Trolox stock solution
in methanol (4 mmol/L) was used to generate the standard line
(concentration range 0e4.0 mmol/L). The results of antioxidant
activity determinations are expressed as Trolox Equivalents (TE). All
determinations were carried out in disposable cuvettes at room
temperature, and the absorbance was measured with Thermo Scientific
NanoDrop 2000c spectrophotometer.