Antioxidant activity of organic solvent extracts from far infrared-treated rice hulls

Methanolic extracts of rice hulls with or without far infrared (FIR) irradiation were sequentially fractionated with solvents (hexane, chloroform, ethyl acetate, butanol, and water), and antioxidant activities of the fractions were analyzed for total phenol contents (TPC), 1,1-diphenyl-2-picrylhydrazy] (DPPH) radical-scavenging capability, reducing power, and antioxidant potency. Yield of chloroform fraction increased significantly from 6.74 to 20.78% after FIR irradiation, while those of ethyl acetate and butanol fractions slightly decreased. Antioxidant activity of ethyl acetate fraction increased significantly by FIR radiation as TPC and DPPH radical-scavenging activity increased from 0.07 to 0.19 mM and 30.09 to 80.19%, respectively. Lard induction time of ethyl acetate fraction increased from 1.15 to 1.49 hr by FIR radiation. GC-MS analysis indicated amounts of phenolic compounds (3-vinyl-l-oxy benzene and benzaldehyde) in ethyl acetate fraction of FIR-irradiated rice hull methanolic extract were greater than those of nonirradiated ones.