Antioxidant capacity of oat (Avena sativa L.) extracts. 2. In vitro antioxidant activity and contents of phenolic and tocol antioxidants

Oat milling fractions were examined for concentrations of total phenolics, tocols, and phenolic acids and in vitro antioxidant activity to determine t heir potential as dietary antioxidants. Methanolic extracts of pearling fra ctions, flour and aspirations from flaking, and trichomes had high, interme diate, and low antioxidant activities, respectively, evaluated by the beta- carotene bleaching method. Pearling fractions were also highest in total ph enolics and tocols, p-Hydroxybenzoic acid, vanillic acid, caffeic acid, van illin, p-coumaric acid, and ferulic acid were identified and quantified by HPLC. Three avenanthramides and an unidentified ferulate derivative were al so detected. Total phenolic content was significantly correlated with antio xidant activity, and regression equations that predicted antioxidant activi ty from phenolic and tocol concentrations were calculated. Antioxidant acti vity, evaluated by beta-carotene bleaching, was correlated with measures of oxygen radical absorbance capacity and low-density lipoprotein oxidation. These data indicate a potential for oat products, especially those enriched in outer layers of the great, to contribute to dietary intakes of antioxid ant phytonutrients.