4. ABTS radical cation decolorization assay
The method, based on the ability of antioxidant molecules to quench the long-lived ABTS radical cation (ABTS+), of Re et al. (1999) was modified. The ABTS+ was produced by reacting 7 mM ABTS stock solution with 2.45 mM postassium persulphate (final concentration) and allowing the mixture to stand in the dark at room temperature for 12-16 hours before use. The ABTS+ solution was diluted with deionized water and 95 % ethanol (1:1) to an absorbance of 0.70
( ±0.02) at 734 nm. Twenty μl of the extract wasmixed with 6 ml of diluted ABTS+ solution. The decrease of absorbance was recorded at 1, 5, 10,and 30 min after mixing. Trolox (0-30 μg) and vitamin C (0-20 μg) were used as standards, and
results were reported as mg Trolox and vitamin C equivalent per gram of dry weight. In addition,the concentration of a selected extract was varied to find out the effective concentration at 50% inhibition (EC50).