Assay of ABTS radical scavenging activity
ABTS radical-scavenging activity of the hydrophilic fractions was determined by a procedure reported by Miller and Rice-Evans (1997). The ABTSradical dot+ solution was prepared by mixing 8 mM of ABTS salt with 3 mM of potassium persulfate in 25 ml of distilled water. The solution was held at room temperature in the dark for 16 h before use. The ABTSradical dot+ solution was diluted with 95% ethanol (approximately 600 μl ABTS to 40 ml 95% ethanol), in order to obtain an absorbance between 0.8 and 0.9 at 734 nm. Fresh ABTSradical dot+ solution was prepared for each analysis. Antioxidant or standard solutions, 20 μl, were mixed with 1 ml of diluted ABTSradical dot+ solution and incubated at 30 °C. The absorbance at 734 nm was read every minute for 30 min using the Safire microplate reader. Ethanol (95%) was used as a blank. Trolox with concentrations from 0 to 500 μM was used as a standard. The free-radical-scavenging activity was expressed as μmoles of Trolox per gram of sample (μmol TE/g fw or dw).