Isolation and Identification of Phenolic Antioxidants in Black Rice Bran

• Published in: Journal of food science 2015-02, Vol.80 (2), p.C262-C268
• Main Authors: Jun, Hyun‐Il, Shin, Jae‐Wook, Song, Geun‐Seoup, Kim, Young‐Soo
• Format: Article
• Language: English
• Subjects: 2,2-diphenyl-1-picrylhydrazyl; acetone; antioxidant activity; Antioxidants; Antioxidants - analysis; Assaying; Benzothiazoles; Biphenyl Compounds; black rice; black rice bran; butylated hydroxytoluene; Cations; Chromatography - methods; Chromatography, High Pressure Liquid; correlation; Coumaric Acids - analysis; Dextrans; Ethyl acetate; Ferulic acid; Food additives; Food science; Functional foods & nutraceuticals; high performance liquid chromatography; Hydroxybenzoates - analysis; Indicators and Reagents; isolation; Oryza - chemistry; phenolic compounds; Phenols; Phenols - analysis; Picrates; Plant Extracts - chemistry; Radicals; Rice; rice bran; Sulfonic Acids; Tandem Mass Spectrometry
• ISSN: 0022-1147; 1750-3841
• DOI: 10.1111/1750-3841.12754

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 EC₅₀values (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 (R²) 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.