Structural studies of a hemicellulose B fraction (B-2) from the cork of Quercus suber

Abstract

Polysaccharide B-2 contains xylose, arabinose, glucose, galactose, 4-O-methylglucuronic acid, and rhamnose in the molar ratio of 17:12:12:6:4:1. The polysaccharide has a backbone of β(1 → 4)- and β(1 → 3)-linked glucopyranosyl, β(1→ 4)-linked xylopyranosyl, and (1 → 4)- and (1 → 6)-linked galactopyranosyl residues. Arabinofuranosyl, rhamnopyranosyl, and some xylopyranosyl and galactopyranosyl groups are present as nonreducing end units. Glucopyranosyluronic acid side chains are attached at O-2 of some xylose residues. The anomeric configurations of the different glycosyl groups were determined by a study of the chromium trioxide oxidation of the acetylated polysaccharide and by nuclear magnetic reasonance spectra of the methylated polysaccharide.