Isolation and structural characterization of the polysaccharide LRGP1 from Lycium ruthenicum

A novel water-soluble glycoconjugate, designated as Lycium ruthenicum glycoconjugate polysaccharide 1 (LRGP1), was isolated from the fruits of Lycium ruthenicum Murr. The crude polysaccharide was obtained by hot water extraction and purified by ion-exchange and gelfiltration chromatography. Its molecular weight was 56.2 kDa determined by HPGPC (high performance gel permeation chromatography). Monosaccharide composition analysis revealed that it was composed of rhamnose, arabinose, xylose, mannose, glucose, and galactose in a molar ratio of 0.65:10.71:0.33:0.67:1:10.41. The existence of O-type carbohydrate–peptide linkage in LRGP1 was demonstrated by β-elimination reaction. On the basis of monosaccharide composition, partial acid hydrolysis, methylation analysis and ESI-MS analysis, LRGP1 was characterized as a branched polysaccharide rich in arabinose and galactose with a backbone composed of (1 → 3)-linked Gal. The branches were composed of (1 → 5)-linked Ara, (1 → 2)-linked Ara, (1 → 6)-linked Gal, (1 → 3)-linked Gal, (1 → 4)-linked Gal and (1 → 2,4)-linked Rha. Arabinose, xylose, mannose, and glucose were located at the terminal of the branches.