2.4.3. Determination of antioxidant activity by ABTS assay
The free radical scavenging activities of orange peel extracts were determined by ABTS radical cation decolorization assay(Re et al., 1999) with minor modifications. A stable stock solution of (ABTS•+) was produced by reacting a 7 mmol/L aqueous solution of ABTS with 2.45 mmol/L potassium persulfate. After the addition of 220 l of diluted (ABTS•+)solution to 80 l of orange peel extract or standard Trolox in ethanol, the absorbance reading was taken at 30◦C, exactly 1 min after initial mixing (A0) and again at 15 min (At). The inhibition percentage of absorbance at 734 nm, using a spec-trofluorometer (SAFAS flx Xenius, Monaco) was calculated between A0 and At, according to the following equation (1)with A0 as initial optical density and At as final optical density.Appropriate solvent blanks were run in each assay.