CONSTITUTION OF A HEMICELLULOSE FROM WHEAT BRAN

Abstract

The hemicellulose prepared from wheat bran by alkaline extraction was an acidic polysaccharide containing arabinose (50.0%), xylose (38.5%), and uronic acid (9.0%). Graded hydrolysis with 0.02 N oxalic acid preferentially released 65% of the arabinose with only a small simultaneous production of xylose. Hydrolysis of the full methylated hemicellulose yielded 2,3,4-tri-O-methyl-, 2,3-di-O-methyl-, 2-O-methyl-, and free D-xylose; 2,3,5-tri-O-methyl-, 2,5-di-O-methyl-, and probably 3- and 5-O-methyl-L-arabinose. These data, together with those from periodate oxidation, strongly suggested that the molecule was a highly branched araboxylan. Viscosity measurements and reducing power determinations indicated a degree of polymerization of 300.