Extraction and preparation of rice bran
Rice bran (10 g) was added to 200 mL of extraction solvent containing 0% to 100% acetone, methanol, and ethanol, and stirred for 12 h at room temperature. This procedure was repeated one more time. After centrifuging at 1000 × g for 15 min, extracted solution was filtered through filter paper (Whatman No. 4), then the supernatant was pooled and made up to 400 mL with each extraction solvent. These extract solutions were analyzed for their DPPH radical scavenging ability, total phenolic and total flavonoid contents to select effective extraction solvent. The selected extrac- tion solvent was evaporated at 40 ◦ C and freeze-dried to determine extraction yield of rice bran. The extracts were then dissolved in
40% acetone at a concentration of 0 to 1500 μg/mL to analyze
antioxidant activity.