THE STRUCTURE OF A GALACTOMANNAN FROM THE SEEDS OF CASSIA NODOSA ¹

Abstract

A new galactomannan has been isolated as a water soluble component from the defatted seeds of Cassia nodosa. Fractional precipitation with ethanol, electrophoresis, displacement chromatography and acetylation followed by deacetylation revealed the homogeneous nature of the polysaccharide. Acid hydrolysis followed by separation of the hydrolyzate by paper partition chromatography and subsequent estimation of the sugars by periodate oxidation method and also spectrophotometrically using phenolsulphuric acid reagent revealed the presence of D–galactose and D–mannose in the ratio of 1:3.5 in the galactomannan. Hyydrolysis of the methylated polysaccharide yielded 2,3,4,6,tetra–O–methyl–D–galactose (1 mole), 2,3,6–tri–O–methyl–D–mannose (2.5 moles) and 2,3–di–O–methyl–D–mannose (1 mole). Determination of the terminal groups by periodate oxidation of the polysaccharide and subsequent titration of formic acid liberated corresponds to 22.75 per cent which is in close agreement to that revealed by methylation studies, 22.1 percent. The polysaccharide is branched and contains α–linked D–galactopyranose end groups combined with 1,4– and 1,4,6–linked β–D–mannopyranose units. Graded hydrolysis of the polysaccharide and sequential Chromatographie examination of the hydrolyzate at various intervals indicated that galactose was the first sugar released.