2.4.3. FRAP Assay

The reduction capacity of the HI extract was assessed by ferric reducing antioxidant power (FRAP) assay (analyzes the reduction of Fe3<sup>+</sup>-TPTZ to the blue-colored Fe2<sup>+</sup>-TPTZ) using a slight modified previously described method [20]. Briefly, a quantity of 25 μL sample was incubated with 175 μL FRAP reagent (300 mM acetate buffer, pH 3.6: 10 mM TPTZ in 40 mM HCl: 20 mM FeCl3·6H2O in 40 mM HCl, 10:1:1, *v*/*v*/*v*) in the dark for 30 min. The absorbance was measured at 593 nm and the results were expressed as TE per dw extract (mg TE/g dw extract). This assay was done only on the richest polyphenolic HI extract.
