By addition
of 200 mL daily fresh prepared FRAP reagent, which consisted of 10
volumes of 300 mmol/L acetate buffer (pH 3.6), 10 volumes of
20 mmol/L FeCl3 and one volume of 10 mmol/L TPTZ in 40 mmol/L
HCl, the ferric TPTZ complex is reduced to its iron(II) form by
antioxidants. After 8 min, the absorbance was measured by the
microplate reader at 595 nm.