The main building components of arabinoxylans (AX) are α-L-arabinose and β-D-xylose, but their structure varies largely with cultivar source and tissue. Cereal grains are the best known and most studied source of AX. Traditionally, AX are classified into water-extractable (WE-AX) and non-extractable AX (WN-AX). WN-AX are fixed in the cell wall by non-covalent and covalent bonds with other AX molecules or with other cell wall constituents. In contrast, WE-AX are loosely bonded to the cell wall by crosslinking with other components. A part of the AX from wheat flour, wheat bran can be extracted with water, yielding a WE-AX-containing fraction. Treatment of the water-non-extractable residue with Ba(OH)2 solutions or with an alkaline solution of H2O2 partly solubilizes WN-AX, yielding an alkali-solubilized AX-rich fraction.
