The antioxidant activity was determined using the ABTS, DPPH
and b-carotene methods. For the ABTS assay, the procedure followed
the method of Re et al. (1999) with minor modifications.
The ABTS radical cation (ABTS+) was generated by the reaction
of 5 mL of aqueous ABTS solution (7 mM) with 88 lL of 140 mM
(2.45 mM final concentration) potassium persulphate. The mixture
was kept in the dark for 16 h before use and then diluted with ethanol
to obtain an absorbance of 0.7 ± 0.05 units at 734 nm using a
spectrophotometer. The fruit extracts (30 lL) or a reference substance
(Trolox) were allowed to react with 3 mL of the resulting
blue–green ABTS radical solution in the dark. The decrease of
absorbance at 734 nm was measured after 6 min. Ethanolic solutions
of known Trolox concentrations were used for calibration.
The results are expressed as micromoles of Trolox equivalents
(TEs) per gram of fresh weight (lmol of TEs/g of f.w.).