CONSTITUTION OF THREE HEMICELLULOSES FROM THE WOOD OF ENGELMANN SPRUCE (PICEA ENGELMANNI)

Abstract

An arabino-4-O-methylglucuronoxylan (10:70:12), a water-soluble galactoglucomannan (1:1:3), and an alkali-soluble galactoglucomannan (0.2:1:3) have been isolated in yields of 8.0, 1.0, and 8.1% from the wood of Engelmann spruce (Picea engelmanni). The xylan consisted of a linear framework of (1 → 4)-linked β-D-xylose residues to which were directly attached single side chains of (1 → 2)-linked 4-O-methyl-α-D-glucuronic acid and (1 → 3)-linked α-L-arabinofuranose residues. The galactoglucomannans were both composed of a backbone of (1 → 4)-linked β-D-mannose and β-D-glucose residues, some of which carried directly attached side chains of (1 → 6)-linked α-D-galactopyranose residues. Partial hydrolysis of the water-soluble galactoglucomannan yielded, among other oligosaccharides, a trisaccharide composed of galactose, glucose, and mannose residues. It is concluded that the main polysaccharides in the wood of Engelmann spruce are the same as those in most other gymnosperms. In the bark of this tree, the water-soluble galactoglucomannan is replaced by one or several polysaccharides of an entirely different composition.