In this study, DPPH method (Brand-Williams, Cuvelier, & Berset,
1995; Chew et al., 2008) was used to determine free radical scavenging
property of phenolic compounds. For each solution,
different concentrations were tested using ascorbic acid as a standard
for calibration and also calculated as mg ascorbic acid equivalent
per 100 g rice (mg AA/100 g). Aliquot of 3.00 mL of
5.0105 mol/L DPPH solution was added into the extract
(1.00 mL). Subsequently, the mixture was kept for 30 min in the
dark, and measured the absorbance at 515 nm. Antioxidant activity
of the sample was expressed as EC50 and ascorbic acid equivalent.
EC50 is defined as the amount of antioxidant required to reduce the
initial DPPH concentration by 50%.