Determination of ferric reducing antioxidant power
(FRAP)
The FRAP was performed according to methods
described by Benzie and Strain (1999). Briefly,
freshly prepared FRAP reagent consisted of 0.3 M
acetate buffer (pH 3.6), 10 mM TPTZ in 40 mM
HCl and 20 mM FeCl3 in a ratio of 10:1:1 (v/v/v).
The 200 μL of rice extract was mixed with 1.3 mL
of the FRAP reagent and after 30 min of incubation
at 37°C, absorption was measured at 595 using a
spectrophotometer. Aqueous or methanolic solutions
of known Fe(II) concentration are used for calibration
of the FRAP assay. FRAP values, expressed as
mmol of Fe(II) equivalent per g rice, was obtained
by comparing the absorption change in the test
mixture with doses obtained from Fe(II) standard
concentrations curve.