New studies on gum ghatti (Anogeissus latifolia) Part III: Structure characterization of a globular polysaccharide fraction by 1D, 2D NMR spectroscopy and methylation analysis

The structure of a globular gum ghatti fraction (FS) with low surface tension was investigated using methylation–GC–MS, 1D (1H, 13C) and 2D (COSY, TOCSY, HMQC and HMBC) NMR spectra. FS was obtained from the supernatant after sequential ethanol precipitation of aqueous gum ghatti (Gatifolia SD) solutions after 80% (v/v) ethanol. FS is proposed to be a highly branched polysaccharide with small amount of acetyl substitution:R can be represented by the following groups: →2,3-Manp1→, →3,4-Glcp1→, →4-Galp1→, T-α-l-Araf 1→, T-GlcpA1→,T-Galp1→ and T-l-Arap 1→. Galactose has the -β-d configuration, while the arabinose and rhamnose are in α-l form.