ARS | Publication request: ANTIOXIDANT ACTIVITY AND PHENOLIC ANTIOXIDANT CONTENTS OF OAT FRACTIONS

Submitted to: Oat Newsletter
Publication Type: Abstract Only
Publication Acceptance Date: July 26, 1998
Publication Date: N/A

Technical Abstract: The potential of oat fractions to contribute to dietary antioxidants was evaluated. Antioxidant activity was measured in methanol extracts of flour, pearlings, bran fines, and trichomes from groats by 1) inhibition of coupled autoxidation of linoleic acid and beta-carotene (AOA), 2) inhibition of copper and peroxyl radical-induced low-density-lipoprotein oxidative damage (LDL-C, LDL-P, respectively), 3) oxygen radical (peroxyl and hydroxyl) absorbance capacity (ORAC-P and ORAC-H, respectively). Pearlings had greater AOA (62-78% inhibition) than flour (53%), bran fines (57%), or trichomes (47%). Pearlings had greater ORAC-P (5.81) and ORAC-H (6.34) than flour (3.40, 3.70) bran fines (2.71, 1.80) and trichomes (2.74, 1.11). LDL-P and LDL-C were greatest for pearlings (3.82 and 3.42, respectively), followed by trichomes (1.54, 1.87), flour (1.26, 0.55), and bran fines (1.28, 0.46). AOA was correlated to LDL-C (r=0.75). Total phenolic content (TPC), determined using the Folin-Ciocalteau phenol reagent (gallic acid equivalents). Pearlings contained the greatest TPC (318 mg/kg), followed by flour (156 mg/kg), trichomes (139 mg/kg), and bran fines (107 mg/kg). TPC was correlated to AOA, ORAC-P and LDL-C. Phenolic compounds were separated by HPLC. Tannic acid, p-hydroxy-benzoic acid, vanillic acid (VA), caffeic acid (CA), syringic acid, vanillin, p-coumaric acid, and ferulic acid were identified and quantified in each sample. AOA was correlated to VA and CA contents. LDL-C was correlated to CA. Three peaks correlated to AOA and LDL-C were tentatively identified as avenanthramides. A fourth peak, with a spectrum similar to catechin (a flavan-3-0l), was correlated with AOA and LDL-C.