Effect of periodate oxidation and borohydride reduction on the chemical structure and chain conformation of arabinoxylan

Artikel i vetenskaplig tidskrift, 2026

The effect of periodate oxidation and borohydride reduction on arabinoxylan (AX) in aqueous solution was investigated using ¹³C NMR spectroscopy and small-angle X-ray scattering (SAXS). AX consists of a xylose backbone, which is mono- or di-substituted with arabinose. We show that at a ring-opening modification degree of 21%, periodate oxidation occurs predominantly on arabinose, and shows a preference for arabinose linked to di-substituted xylose units over the mono-substituted. With a higher degree of modification of 33%, arabinose at the mono-substituted position and unsubstituted xylose units are also modified. At 33% a large portion of oxidizable AX residues have been ring-opened, yet SAXS reveals no significant changes in chain conformation and only a minor reduction (10%) in persistence length for the oxidized-reduced dialcohol AX. With increasing degree of oxidation, dialdehyde AX instead show an increasing tendency for aggregation, attributed to chain cross-linking. Upon reduction of the dialdehyde and cross-linked groups to dialcohol AX, the chains revert back to having repulsive interactions, acting as chains in a good solvent environment.