Arabinoxylan is a form of the hemicellulose[1] xylan found in both the primary and secondary cell walls of plants which in addition to xylose contains substantial amounts of another pentose sugar, arabinose.
Whilst arabinose has been found linked to xylan in non-commelinid plants, ferulic acid has not been reported on these and unlike feruloyl-arabinoxylan these arabinoxylans are not monophyletic.
[2][3] These feruloyl units can undergo radical oxidative coupling forming ferulic acid dehydrodimers and possibly higher oligomers that covalently crosslink arabinoxylan chains.
[4] Due to a low degree of crosslinking into the cell wall, some of this endosperm arabinoxylan is extractable in water, giving rise to soluble dietary fiber.
In lignified cell walls, there is strong evidence that feruloyl residues on arabinoxylan can be crosslinked into the lignin polymer, increasing recalcitrance to digestion.