Isolation and structural characterization of a polysaccharide LRP4-A from Lycium ruthenicum Murr

A complex polysaccharide, termed LRP4-A, was isolated from the fruit of Lycium ruthenicum Murr. and its structure was characterized. The crude polysaccharide LRP was obtained from the fruit of L. ruthenicum Murr. using hot water extraction followed by ethanol precipitation. The water-soluble polysaccharide LRP4-A was purified from LRP by anion-exchange chromatography and gel filtration chromatography. Its molecular weight was 1.05×10(5) Da. Monosaccharide composition analysis revealed that LRP4-A mainly consisted of rhamnose, arabinose, glucose, and galactose in the molar ratio of 1:7.6:0.5:8.6, with a trace of xylose. Structure of the polysaccharide LRP4-A was characterized using a series of analytical techniques, including methylation analysis, partial acid hydrolysis, IR, NMR, and ESI-MS. LRP4-A was identified to be a highly branching polysaccharide with a backbone of β-(1→6)-linked galactose partially substituted at O-3 position. The branches were composed of (1→3)-linked-Gal, (1→3)-linked-Ara, (1→5)-linked-Ara, and (1→2,4)-linked-Rha. Arabinose, galactose, and glucose were located at the termini of the branches.