Radical DPPH˙ scavenging activity
Five different concentrations of rice extract (0, 0.1, 0.2, 0.4 and 0.8 mg/mL) were added to 3 mL of 200 µM DPPH˙ solution in methanol. After incubation at room temperature for 30 min, the absorbance at 517 nm was measured using spectrophotometer (Libra S22, Biochrom, England). The standard solution for DPPH˙ scavenging activity was Trolox which was used in the range of 0-0.02 mg/mL. The obtained regression equation was y = 4239.5x-10.818 (R2 = 0.930). The percentage of inhibition was expressed using the following equation