LAUSR

Abstract AY60 was a fraction precipitated from Acacia seyal gum by 60% ethanol, and its detailed structure was elucidated by methylation analysis and 1D/2D NMR spectroscopy. AY60 (Mw~92.4 kDa) was found to be a highly branched polysaccharide, and the terminal residues accounted for about 29.76% of total residues, which were t-Araf (26.59%), t-Rhap (2.25%) and t-Galp (0.92%) respectively. The branching residues included →3,6-Galp 1→ (15.81%), →3,4-Galp1→ (13.59%) and →3,4,6-Galp1→ (11.25%). NMR spectroscopy (1H NMR, 13C NMR, 1H–1H COSY, TOCSY, HSQC and HMBC) confirmed that the backbone of AY60 was composed of 1,3-linked galactopyransyl residues substituted at O-4 and O-6 positions. The side chains were mainly composed of →4)-β-GalpA-(1→ (14.43%) and →3)-α-Araf-(1→ (2.25%), and terminated by arabinofuranosyl (Araf) and occasionally by rhamnopyranosyl (Rhap) or glacuronopyranosyl (Glap) residues.