STRUCTURAL INVESTIGATION OF A WATER-SOLUBLE GALACTOMANNAN FROM THE SEEDS OF CASSIA-ALATA LINN

A water-soluble galactomannan isolated from the endosperm of the seeds of Cassia alata by extraction with hot water, has .**GRAPHIC**. + 20.degree. and contains D-galactose and D-mannose in 1:3.3 molar ratio. The molecular weight of the galactomannan has been found to be 1.1 .times. 106 to 2.3 .times. 106 by gel filtration method. Methylation analysis gives 2,3,4,6-tetra-O-methyl-D-galactose, 2,3,6-tri-O-methyl-D-mannose, and 2,3-di-O-methyl-D-mannose in a molar ratio of 1:2.3:1. The results of periodata oxidation are in agreement with those of methylation studies. Partial acid hydrolysis of the galactomannan furnishes two dissaccharides, two trisaccharides and a tetrasaccharide. A mixture of tetrasaccharides has also been characterized. The anomeric configuraton of the sugar residues have been determined by chromatin trioxide oxidation. These results suggest that the galactomannan consists of a main chain of .beta.-(1-.fwdarw. 4) linked D-mannopyranosyl residues, 23% of which are branched through O-6 by single .alpha.-D-galactopyranosyl stubs. An aq. solution of the galactomannan (1%) has a viscosity of 1600 cP. The galactomannan interacts with Xanthomonas polysaccharide to give a gel of considerable strength.