Resumen de Structural determination and chemical modifications of the polysaccharide from seeds of prosopis chilensis mol. (stuntz)
Betty Matsuhiro, Luis C Presle, Carmen Saenz, Carlos Urzúa
The polysaccharide extracted from Prosopis chilensis seeds in acidic medium showed by total hydrolysis and gas-liquid chromatography analysis of the alditol acetates to be composed of galactose and mannose in the molar ratio 1.0:1.9. Studies by methylation and ¹H and13C NMR spectroscopy indicated that the polysaccharide was a galactomannan with a chain of D-mannopyranosyl residues linked beta 1 which carried alternatively alpha-D-galactopyranosyl residues at position O-6 of D-mannose units. The chemical modification of the galactomannan by reaction with sodium chloroacetate afforded in 95.3% yield, a derivative which gave a very viscous solution with water. By titration it was determined a carboxymethylation degree of 0.42 indicating that 64% of the alcoholic groups were etherified. Reaction of the galactomannan with TEMPO-NaCl-NaOBr system gave a water soluble polysaccharide. The DEPT 135º NMR spectrum indicated that the primary alcoholic groups of galactopyranosyl and unbranched mannopyranosyl residues were fully oxidised
