3.4.3. Ferric Reducing Antioxidant Power (FRAP) Assay

FRAP assay was performed as previously reported [53] by using a 96-well microplate to monitor the reduction of Fe³⁺ tripyridyl triazine (TPTZ) to blue-colored Fe²⁺-TPTZ. Fresh working solution was prepared by mixing 10 volumes of acetate buffer (300 mM, pH 3.6), 1 volume of TPTZ (10 mM in 40 mM HCl) and 1 volume of FeCl₃·6 H₂O (20 mM). CYS or EUC (concentrations as for ABTS assay) were incubated with FRAP solution for 10 min, and the absorbance was read at 593 nm with Trolox as standard as described above.