Antioxidants in oats: Mono‐esters of caffeic and ferulic acids

Abstract

Abstract Two‐dimensional thin‐layer chromatography has shown the presence of 24 phenolic antioxidants in oats, and the present paper deals with the identification of five of these. Two of them have been isolated by column chromatography and characterised. One consists of the homologues, n‐hexacosyl caffeate and n‐octacosyl caffeate (proportions, 3:1, approximately) and the other, 26‐ O ‐caffeoyl‐26‐hydroxy‐hexa‐cosanoic acid with 28‐ O ‐caffeoyl‐28‐hydroxyoctacosanoic acid (proportions, 3:1, approximately). Evidence is presented for the probable structures of the remaining three antioxidants, based on two‐way thin‐layer chromatographic comparison with the synthetic ferulates: n‐hexacosyl ferulate, 26‐ O ‐feruloyl‐26‐hydroxyhexacosanoic acid and hexacosane‐1,26‐diol monoferulate. The preparation of these ferulates is described, and in addition, that of two caffeates, n‐hexacosyl and n‐dodecyl. The antioxidant activities of the above compounds were measured.