Graminaceous cell walls contain arabinoxylans in which some of the Araf residues are 5-O-feruloylated. In the present study, mild acid hydrolysis of (pentosyl-H-3)-labelled Festuca arundinacea cell walls yielded the well-characterized 5-O-Fer-L-Ara (1) and at least seven new (E)-feruloylated oligosaccharides, 2-8. Compound 2 was a feruloylated disaccharide, Fer-(D-Xylp→L-Ara); electrophoresis in molybdate buffer, Smith degradation and methylation analysis showed a (1→2)-linkage. H-1 and C-13 NMR data and susceptibility to commercial β-D-xylosidase indicated a β-linkage. Graded alkaline hydrolysis of 2 showed no evidence for more than one ester group. Hydrolysis with commercial β-xylosidase yielded 5-O-feruloyl-L-arabinose. Compound 2 was thus 2-O-β-D-xylopyranosyl-(5-O-feruloyl)-L-arabinose. We propose that 2 was furanose-linked to a xylan backbone in the intact polymer. Compounds 3-8 also appeared to be O-feruloyl oligosaccharides with a former Araf residue at the reducing terminus. Mild acid hydrolysis of cell walls from twenty other species of grass and one palm also yielded compounds 1-3, and most or all of 4-8. Therefore, these complex feruloylated side-chains of arabinoxylans are widespread or universal in the Gramineae. Their possible biological roles are discussed.
Oligosaccharides, Gramineae, Festuca arundinacea, tall fescue grass, feruloyl esters, arabinoxylans, plant cell walls
Publication DOI: 10.1016/S0031-9422(96)00649-8Journal NLM ID: 0151434Publisher: Elsevier
Institutions: ICMB, DBS, The University of Edinburgh, Daniel Rutherford Building, The King's Buildings, Mayfield Road, Edinburgh EH9 3JH, U.K.
Methods: 13C NMR, 1H NMR, methylation, gel filtration, GC-MS, sugar analysis, mild acid hydrolysis, Smith degradation, HPLC, alkaline hydrolysis, paper electrophoresis, radioactivity assay, paper chromatograph
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