Phenolic Acid, Tocopherol and Carotenoid Compositions, and Antioxidant Functions of Hard Red Winter Wheat Bran

An electron spin resonance (ESR) spectrometry study was conducted to examine the free radical scavenging properties of bran extracts of Alliance and Wichita wheat using hydroxyl radical (HO^•), 2,2-diphenyl-1-picryhydrazyl radical (DPPH^•), and superoxide radical anion (O₂^•-) and their chelating capacities against Cu²⁺. Also reported is the radical cation 2,2‘-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS^•+) scavenging activity, oxygen radical absorbing capacity (ORAC), and chelating property against Fe²⁺ of the bran extracts measured by the spectrophotometric methods. Significant radical scavenging and chelating capacities were detected in the bran extracts, along with significant levels of phenolic acids, tocopherols, and carotenoids. Ferulic acid, with a concentration range of 130.60−146.38 μg/g, was the predominant phenolic acid in all of the tested bran samples and accounted for 53−67% of total phenolic acids on a weight basis. Total tocopherol concentration ranged from 1.87 to 2.95 μmol/100 g of bran, whereas total carotenoid level was 0.20−0.33 μmol/100 g of bran. In addition, both wheat variety and growing conditions might significantly alter antioxidant properties and concentrations of beneficial components in wheat bran.

Keywords: ESR; wheat; bran; antioxidants; phenolic acid; tocopherol; carotenoid; chelating; radical