title: Isolation and identification of phenolic antioxidants in black rice bran.
abstract: Black rice bran contains phenolic compounds of a high antioxidant activity. In this study, the 40% acetone extract of black rice bran was sequentially fractionated to obtain 5 fractions. Out of the 5 fractions, ethyl acetate fraction was subfractionated using the Sephadex LH-20 chromatography. The antioxidant activity of phenolic compounds in the extracts was investigated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay, 2,2-azino-bis-(3-ethylenebenzothiozoline-6-sulfonic acid) (ABTS) radical cation assay, reducing power. The subfraction 2 from ethyl acetate fraction had the highest total phenolic contents (TPC) (816.0 μg/mg) and the lowest EC50 values (47.8 μg/mL for DPPH radical assay, 112.8 μg/mL for ABTS radical cation assay, and 49.2 μg/mL for reducing power). These results were 3.1, 1.3, and 2.6 times lower than those of butylated hydroxytoluene (BHT), respectively. At a concentration of 100 μg/mL, the antioxidant activity and TPC of various extracts was closely correlated, with correlation coefficients (R(2) ) higher than 0.86. The major phenolic acid in subfraction 2 was identified as ferulic acid (178.3 μg/mg) by HPLC and LC-ESI/MS/MS analyses. Our finding identified ferulic acid as a major phenolic compound in black rice bran, and supports the potential use of black rice bran as a natural source of antioxidant.
authors.affiliation: Dept. of Food Science & Technology, Chonbuk National Univ, Jeonju, 561-756, South Korea.
authors.forename: Hyun-Il
authors.initials: HI
authors.lastname: Jun
authors.forename: Jae-Wook
authors.initials: JW
authors.lastname: Shin
authors.forename: Geun-Seoup
authors.initials: GS
authors.lastname: Song
authors.forename: Young-Soo
authors.initials: YS
authors.lastname: Kim
mesh_terms: D000975:Antioxidants / Q000032:analysis*; D052160:Benzothiazoles; D001713:Biphenyl Compounds; D002845:Chromatography / Q000379:methods; D002851:Chromatography, High Pressure Liquid; D003373:Coumaric Acids / Q000032:analysis; D003911:Dextrans; D062385:Hydroxybenzoates / Q000032:analysis; D007202:Indicators and Reagents; D012275:Oryza / Q000737:chemistry*; D010636:Phenols / Q000032:analysis*; D010851:Picrates; D010936:Plant Extracts / Q000737:chemistry*; D013451:Sulfonic Acids; D053719:Tandem Mass Spectrometry
chemical_list: D000975:Antioxidants; D052160:Benzothiazoles; D001713:Biphenyl Compounds; D003373:Coumaric Acids; D003911:Dextrans; D062385:Hydroxybenzoates; D007202:Indicators and Reagents; D010636:Phenols; D010851:Picrates; D010936:Plant Extracts; D013451:Sulfonic Acids; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; C010574:biphenyl; C025614:sephadex; C004999:ferulic acid; C004931:1,1-diphenyl-2-picrylhydrazyl; C017616:phenolic acid
keywords: antioxidant activity; black rice bran; ferulic acid; isolation; phenolic compounds