Structural investigation of the polysaccharide of Spondias mombin gum

The polysaccharide, isolated from Spondias mombin gum exudate, was subjecte d to acid hydrolysis and Smith degradation processes in order to investigat e its relevant structural features. Chemical and spectral evidence suggeste d the existence of small blocks of (1 --> 3)-linked beta-D-galactosyl resid ues, interspersed with 6-O substituted D-galactosyl residues, in the backbo ne of the investigated structure; these residues are also in the side-chain s. In addition, there was arabinose, up to three units long, predominantly in the form of furanosyl residues (terminal, 2-O- and 3-O-linked). Arabinop yranosyl residues (terminal and 2-O-linked) as well as rhamnose and mannose are also present in minor amounts. Uronic acids, beta-D-glucuronic acid an d 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 difficu lt to remove from the core. C-13-NMR spectroscopy confirmed the results obt ained by chemical methods, and showed the presence of reducing terminal sug ar residues and internal acetyl groups. (C) 2000 Elsevier Science Ltd. All rights reserved.