A Non-ionic Seed Gum from Ipomoea palmata

Department of Chemistry, University of Allahabad, Allahabad-211 032

Manuscript received 10 June 1988, revised 3 November 1988, accepted 18 November 1988

A polysaccharide has been extracted from Ipomoea palmata seeds with cold acidulated water, and purified to give a water soluble product contain­ing D-galactose and D-mannose in 2 ; 3 molar ratio. Acid-catalysed frag­mentation, periodate oxidation, methylation and enzymic hydrolysis showed that the seed gum has a branched structure consisting of a linear chain of β-D-(1→4) linked mannopyranosyl units, some of which are subs­tituted at 0— 6 by two α.-D-(1→6) galactopyranosyl units mutually linked glycosidically Methylation analysis of the galactomannan afforded 2,3,4- tri- and 2,3,4,6-tetra-O-methylgalactose, along with 2,3-di- and 2,3,6-tri-O­methylmannose, in the molar ratio of 1 : 1: 1 : 2 Both the methylation and periodate oxidation studies showed 39 7% of end-groups The significance of these results, together with the findings of partial hydrolysis with acid are discussed in relation to ascertaining the structure of the repeating unit of the polysaccharide.