2.6.2. ABTS+ assay
The antioxidant capacity was estimated in terms of radical scavenging
activity, following the procedure described by Re et al.
(1999) with slight modifications (Rufián-Henares and Morales,
2007). Briefly, ABTS+ was produced by reacting 7 mM ABTS stock
solution with 2.45 mmol/l potassium persulphate and allowing
the mixture to stand in the dark at room temperature during 12–
16 h before use. The ABTS+ solution (stable for 2 days) was diluted
with 5 mmol/l phosphate buffered saline (pH 7.4) to an absorbance
of 0.70 ± 0.02 at 730 nm. After addition of 100 ll of extract or trolox
standard to 1 ml of diluted ABTS+ solution, absorbance reading
was taken at 20 min. using a Lambda 25 spectrophotometer (Perkin
Elmer, Waltham, MA, USA). Calibration was performed, as described
previously, with a trolox stock solution. Results were
expressed as lmol equivalents of trolox per g of sample.