2.10. Antioxidant activity assessed by ABTS radical
scavenging activity
ABTS was dissolved in water (7 mmol/L).The ABTS radical cation
(blue in colour) was produced by reacting the ABTS stock solution
with 2.45 mmol/L potassium persulphate (final
concentration) and allowing the mixture to stand in the dark
at room temperature for 12–16 h before use. For testing samples,
the ABTS radical cation stock solution (5 mmol/L) was diluted
with phosphate-buffered saline, pH 7.4, to an absorbance of
0.70 at 734 nm. After the addition of 980 L of diluted ABTS to
20 L of sample, the absorbance reading was taken 5 min after
the initial mixing.The percentage ABTS scavenging activity was
calculated as: