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

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

COc1cc(/C=C/C(=O)OC[C@@H]2OC(O)[C@H](O)[C@H]2O)ccc1O

326.301 g/mol (C₁₅H₁₈O₈)

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

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6	C7	C8	C9	C10
2	bDXylp	103.8-104.2	74.1	76.7	70.3	66.4
5	xXFer	127.8	112.5	148.8	149.2	116.8	124.6	147.6	115.1	170.2	57.0
	aLAraf	101.4	90.2	76.2	81.6	64.8


1H NMR data:
missing...

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

COc1cc(/C=C/C(=O)OC[C@@H]2O[C@@H](O)[C@H](O[C@@H]3OC[C@@H](O)[C@H](O)[C@H]3O)[C@H]2O)ccc1O

458.416 g/mol (C₂₀H₂₆O₁₂)