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Structural investigation of the polysaccharide of Spondias mombin gum

Abstract:

The polysaccharide, isolated from Spondias mombin gum exudate, was subjected to acid hydrolysis and Smith degradation processes in order to investigate its relevant structural features. Chemical and spectral evidence suggested the existence of small blocks of (1→3)-linked β-D-galactosyl residues, interspersed with 6-O substituted D-galactosyl residues, in the backbone of the investigated structure; these residues are also in the side-chains. In addition, there was arabinose, up to three units long, predominantly in the form of furanosyl residues (terminal, 2-O- and 3-O-linked). Arabinopyranosyl residues (terminal and 2-O-linked) as well as rhamnose and mannose are also present in minor amounts. Uronic acids, β-D-glucuronic acid and its 4-O-methyl analogue, are attached at the C-6 and C-4 positions of the galactose moieties in the backbone. These sugar acid residues were difficult to remove from the core. 13C-NMR spectroscopy confirmed the results obtained by chemical methods, and showed the presence of reducing terminal sugar residues and internal acetyl groups.