Acetylation of viscous polysaccharide, extracted from Natto, containing D-galactose, L-arabinose, and D-xylose, afforded an acetylated polysaccharide of molecular weight of 10000, CH₃CO content of 42.99%, and not containing any ash. Deacetylation of this polysaccharide afforded electrophoretically single polysaccharide with molecular weight of ca. 5300 per one terminal group. The content of these three kinds of componental sugars is approximately equal and it was assumed that the polysaccharide has a molecular weight of 5300-5900 and contains approximately equimolar amount of L-arabinose, D-xylose, and D-galactose.
Methylation of the acetylated compound afforded a methylated polysaccharide with 43.28% of CH₃O. Hydrolysis of this methylated polysaccharide afforded 3, 5-O-dimethyl-arabinose, 2, 4-O-dimethylxylose, 2, 4-O-dimethylgalactose, 2, 3, 4-O-trimethylgalactose, and 2, 3, 4, 6-O-tetramethylgalactose. It therefore follows that the original polysaccharide is composed of arabinose, xylose, and galactose bonded with each other at 1- and 2-positions of L-arabofuranose, 1- and 3-positions of D-xylopyranose, and 1- and 6-positions of D-galactopyranose, having branched chain bonded at 3-position of the galactose residue, and the non-reducing terminal sugar is considered to be galactose.