Identification and function of antioxidants from oat groats and hulls

Abstract
Antioxidant components of methanolic extracts of groats and hulls from Ogle oats were identified and quantified by using gas chromatography‐mass spectrometry (GC‐MS) and gas chromatography after N,O‐bis(trimethylsilyl)acetamide derivatization. Ferulic, p‐coumaric, vanillic, p‐hydroxybenzoic, 4‐hydroxyphenylacetic acids and vanillin and catechol were quantified in groat and hull extracts. Additionally, caffeic acid in groat extracts, and o‐coumaric, sinapic and slaicylic acids in hull extracts were quantified. Extracts from groats and hulls at levels of 0.05, 0.1, 0.2, and 0.3% w/w, based on total phenolic content, were added to soybean oil, and their antioxidant effectiveness was compared with that of 0.02% w/w tertiary butylhydroquinone (TBHQ) and a control (no additives) at 60°C in the dark by measuring peroxide values. Antioxidant activities of both extract sources increased with increased concentration. During 20 d of storage, the groat extract (0.3%) was not significantly different from TBHQ after day 16, and hull extracts (0.2 and 0.3%) were not significantly different from TBHQ on day 20. Oils containing pure phenolics at the same concentrations measured in the groat and hull extracts oxidized more quickly than did oils containing the extracts.

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