The core carbohydrate structure of Acacia seyal var. seyal (Gum arabic)

The structure of gum arabic (Acacia seyal) has been studied using methylation analysis and 2D (COSY, TOCSY, HMQC and HMBC) NMR spectroscopy. Galacturonic acid (13.66%) is a major component not previously identified. The backbone is made up of 1,3-linked galactopyranosyl (Galp) residues substituted at O-2, O-6 or O-4 positions, which are terminated with mainly arabinofuranosyl (Araf), galacturonopyranosyl (GalpA), rhamnopyranosyl (Rhap), but occasionally with arabinopyranosyl (Arap), and glucuronopyranosyl (GlcpA) residues. There are long side chains of →3)-α-l-Araf-(1→ and →2)-α-l-Araf-(1→ linked to the backbone.

Graphical abstractProposed structure of the carbohydrate in Acacia seyal. R is one of these following residues: T-Rhap1. →, T-l-Araf 1. →, T-l-Arap 1. →, TGlcpA1. →, T-GalpA1. →, T-l-Araf 1. → 3-l-Araf 1. →, T-l-Araf 1. → 2-l-Araf 1→. The galactose moieties are in -β-d form, with the galacturonic acid, arabinose and rhamnose in α-L form.Figure optionsDownload full-size imageDownload as PowerPoint slide