Structural features of a new water-soluble polysaccharide from the gum exudates of Amygdalus scoparia Spach (Zedo gum)

A new water-soluble polysaccharide (CZGS-1) with molecular weight of 4860kDa and a specific optical rotation of +31.5° (c 1.0, H₂O), was extracted from the gum exudate of Amygdalus scoparia Spach by hot water, following by purification with DEAE-cellulose A52 and Sephacryl S-400 HR columns. Monosaccharide composition analysis indicates that CZGS-1 was an arabino galactan including Rha, Ara, Xyl, and Gal with a relative molar ratio of 1.1:20:5.2:17.9. The uronic acid content of CZGS-1 was about 6%. Structural features of CZGS-1 was investigated by a combination of partial acid hydrolysis, methylation and GC-MS analysis, periodic acid oxidation and Smith degradation, FT-IR and NMR spectroscopy. The results indicated that CZGS-1 possesses a backbone of →3,6)-β-d-Galp-(1→, →3)-β-d-Galp-(1→, and →3)-α-l-Araf-(1→ residues with side chains attached to O-3 and O-6 positions of 1,3,6-linked β-d-Galp. The side chains are consisted of β-d-Xylp-(1→3)-α-l-Araf-(1→3)-α-l-Araf-(1→), α-l-Rhap-(1→6)-β-d-Galp-(1→), and β-d-GlcAp-(1→6)-β-d-Galp-(1→).