Briefly, a FRAP solution was mixed with 10 mL of 0.3 M sodium acetate buffer solution (pH 3.6), 1 mL of 10 mM 2,4,6-tripyridyl-S-triazine (TPTZ) in 40 mM HCl, and 1 mL of 20 mM FeCl3. The sample (10 lL) was added to 190 lL of FRAP solution as an oxidizing reagent and incubated for 4 min at room temperature.