Structure of a new galactomannan from the seeds of Ipomoea fistulosa

Abstract

The seeds of Ipomoea fistulosa contain a water-soluble galactomannan composed of residues of d-galactose and d-mannose in the ratio 3 : 10. Hydrolysis of the methylated polysaccharide gave 2,3,4,6-tetra- O-methyl- d-mannose (3 mol), 2,3,6-tri- O-methyl- d-mannose (7 mol), and 2,3-di- O-methyl- d-mannose (3 mol). Periodate-oxidation data indicated 22.1% of end groups, and methylation 22.8%. The above findings, together with data on the oligosaccharides formed on partial hydrolysis with acid, showed the galactomannan to consist of a linear chain of (1→4)-linked β- d-mannosyl residues to which α- d-galactosyl groups are attached by (1→6)-linkages.