Identification of 4-O-5 '-coupled diferulic acid from insoluble cereal fiber

The extracts of saponified cereal fibers of whole grains of corn (Zea mays cv. microsperma KOERN.), wheat (Triticum aestivum- L.), spelt (Triticum spe lta L.), and rice (Oryza sativa L.) were investigated for dehydrodimers of ferulic acid using gas-liquid chromatography (GLC) with mass spectrometric detection (CLC-MS) and flame ionization detection (GLC-FID). In addition to the 8,5'-, 8,8'-,,5'-, and 8-O-4'-coupled diferulic acids previously ident ified from other plant materials the 4-O-5'-coupled diferulic acid (E)-3-[4 -[(E)-2-carboxyvinyl]-2-methoxyphenoxy]-4-hydroxy-5-methoxycinnamic acid (4 -O-5'-DFA) was identified in all fibers investigated. This new diferulate w as authenticated by comparison of its mass spectrum and its relative GLC re tention time with those of the synthesized compound. Semiquantitative deter mination of 4-O-5'-DFA showed that it is present at 8-30 mu g/g, approximat ely 70-100 times lower concentrations than the sum of 8,5'-coupled diferuli c acids, the major diferulic acids in the investigated fibers.