CONSTITUTION OF A GLUCOMANNAN FROM TAMARACK (LARIX LARICINA)

Abstract

A hemicellulose fraction containing D-mannose, D-glucose, and D-galactose in a ratio of 70:25:3 has been isolated from tamarack wood. The product was homogeneous under conditions of free boundary electrophoresis and of sedimentation in the ultracentrifuge. Hydrolysis of the fully methylated hemicellulose yielded 2,3,4,6-tetra-O-methyl-D-glucose (1.2%); 2,3,4,6-tetra-O-methyl-D-galactose (2.2%); 2,3,6-tri-O-methyl-D-glucose (24.0%); 2,3,6-tri-O-methyl-D-mannose (68.8%); 2,3-di-O-methyl-D-mannose (1.6%); and 2,3-di-O-methyl-D-glucose (1.7%). This data and that from periodate oxidation indicated that the glucomannan had a linear backbone of approximately 35 (1 → 4) linked β-D-glucopyranose and β-D-mannopyranose units; approximately two thirds of the chains were terminated at the non-reducing ends by D-galactose and the remainder by D-glucose. Branching, if present, must occur through C₆ of the hexoses in the main chain.