Structure of an arabinoxylan from the bark of Persea macrantha (Lauraceae)

An arabinoxylan isolated from the delignified bark of Persea macrantha is composed of l-arabinose (73%) and d-xylose (27%). Partial hydrolysis gave 3-O-d-xylopyranosyl-l-arabinose, 4-O-d-xylopyranosyl-d-xylose, O-d-xylopyranosyl-(1→4)-O-d-xylopyranosyl-(1→4)-d-xylose, and O-d-xylopyranosyl-(1→4)-O-d-xylopyranosyl-(1→4)-O-d-xylopyranosyl-(1→4)-d-xylose. Methylation analysis and periodate oxidation have been performed on the native and the degraded polysaccharides. It is suggested that the polysaccharide contains a backbone consisting of (1→4)-linked β-d-xylopyranosyl residues, each of which is substituted both at O-2 and O-3 with l-arabinofuranosyl and 3-O-d-xylopyranosyl-l-arabinofuranosyl groups. Some of the d-xylosyl residues of the latter side-chains are further substituted either at O-2 and O-4, or at O-3 and O-4, with l-arabinofuranosyl groups.