The free reducing oligosaccharides of gum arabic: aids for structural assignments in the polysaccharide

• Published in: Carbohydrate polymers 2002-02, Vol.47 (2), p.151-158
• Main Authors: Tischer, C.A., Gorin, P.A.J., Iacomini, M.
• Format: Article
• Language: English
• Subjects: Alkalinity; Applied sciences; Degradation; Dialysis; Evaporation; Exact sciences and technology; Free, reducing oligosaccharides; Gum acacia; Natural polymers; Nuclear magnetic resonance spectroscopy; Oxidation; Physicochemistry of polymers; Polysaccharide; Solubility; Starch and polysaccharides; Structural similarity
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/S0144-8617(01)00173-4

Gum arabic contains in small quantities, the free reducing sugars, arabinose, ribose, glucose, mannose, galactose, rhamnose, α- d-Galp-(1→3)-αβ- l-Ara, α- l-Araf-(1→4)-β- d-Galp-(1→6)-αβ- d-Gal, β- d-GlcpA-(1→6)-αβ- d-Galp, α- l-Rhap-(1→4)-β- d- GlcpA-(1→6)-αβ- d-Galp, α- l-Rhap-(1→4)-β- d-GlcpA-(1→6)-β- d-Galp-(1→6)-αβ- d-Galp, a branched pentasaccharide with a chain of α- d-Galp-(1→3)-α- l-Araf-(1→3)-β- d-Galp-(1→6)-αβ- d-Galp substituted at O-4 of Gal p′ with α- l-Ara f units, and a doubly branched heptasaccharide with a chain of α- d-Galp-(1→3)-α- l-Araf-(1→3)-β- d-Galp-(1→6)-αβ- d-Galp, disubstituted, respectively, at O-4 and O-6 of Gal p′ with α- l-Ara f and α- l-Rha p-(1→4)-β- d-Glc pA groups. A small amount of a related heptasaccharide was also present, with non-reducing end units of β-Ara p, in place of those of α-Gal p. These oligosaccharides were characterized by 1D and 2D NMR spectroscopy, ESI-MS, and in three cases, methylation analysis for final confirmation. The oligosaccharides should represent, with the probable exception of the galactosyl reducing ends, side-chain structures present in the gum arabic polysaccharide.