Isolation and structural characterization of a polysaccharide derived from a local gum: Zedo (Amygdalus scoparia Spach)

摘要

In this study, a novel polysaccharide was isolated from a local gum, zedo (Amygdalus scoparia Spach). Chemical composition of the gum and elemental analysis of the isolated polysaccharide were determined. The polysaccharide and its fragments were examined by gas chromatography-mass spectrometry, GC-MS, viscometry, H-1 NMR, and (CNMR)-C-13 spectroscopy. Results obtained from different methods, revealed that a hetero-polysaccharide is the main component of the gum. The amounts of moisture, minerals, protein and lipid were 9.42, 2.23, 1.05, and 0.03 (w/w %), respectively. The amounts of carbon, hydrogen, oxygen and nitrogen obtained from elemental analysis were 38.5, 5.8, 35.3, and 0.3 (w/w %), respectively. The presence of arabinose, galactose, rhamnos, mannose, beta- D-glucose, fructose, galacturonic and glucuronic acids residues were measured by GC-MS analysis. However, conversion of glucose into fructose probably occurred during the analysis, because the temperature of the analysis is high enough. Both carboxylic groups and minerals/salts had a major influence on the rheological properties of the gum. The gum exhibited polyelectrolyte behavior, and its solutions did not follow Newtonian flow behavior. It can be naturally occurred as an anionic polysaccharide. The gum was a highly branched polysaccharide and a member of arabinogalactans family. The main chain contains alpha- L-arabinofuranosyl, alpha- L-Araf, and beta-D-galactopyranonyl, beta-D-Galp, units. The following residues were identified: - 3,4) beta-D-Galp (1 - ; - 3,4,6) beta-D-Galp (1 - ; - 3)- alpha- L-Araf-(1 - ; - 4) beta-D-GlcpA (1 - .; glucosyl residues; and alpha-L- Rhap, (1 - . Terminal residues were: alpha-L- Rhap; and alpha- L-Araf.