Isolation and characterisation of lignin-carbohydrate complexes from the milled-wood lignin fraction of Pinus densiflora sieb. et zucc.

The lignin-carbohydrate complex (LCC-W), isolated from the milled-wood, lignin fraction of Pinus densiflora Sieb. et Zucc., comprised three fractions (W-1,2,3) by gel filtration on Sepharose 4B. W-1 was eluted at the void volume, whereas W-2 and W-3 were included in the gel and had apparent weight-average molecular weights of 5.0 × 10⁵ and 5.0 × 10³, respectively. W-2 and W-3 were homogeneous in ultracentrifugal and electrophoretic analyses. The sedimentation coefficients of W-2 and W-3 were 25.7 and 0.4S, respectively. The chemical composition of W-2 was 38.0% of neutral sugar, 6.2% of uronic acid, 51.5% of lignin, and the corresponding values for W-3 were 73.1, 11.0, and 22.2%. The neutral carbohydrate residues of W-2 and W-3 were l-arabinose, d-xylose, d-mannose, d-galactose, and d-glucose in the ratios 15.8:16.2:37.3:16.7:14.0 and 27.6:16.5:26.1:19.3:10.5, respectively. Based on the results of methylation and Smith-degradation analyses, the carbohydrate moiety of the LCC-W fractions was found to be multiply branched. The major backbone structure was composed of (1→4)-linked d-mannopyranosyl residues. By hydrophobicinteraction chromatography on Phenyl- and Octyl-Sepharsoe CL-4B gels, it is concluded that the LCC-W fractions have a hydrophobic property that is exclusively ascribed to the lignin moiety.