Structural Characterization of an Arabinogalactan-Protein from the Fruits of Lycium ruthenicum

A water-soluble arabinogalactan-protein (AGP), designated LRGP3, was isolated from the fruits of Lycium ruthenicum Mum Its average molecular weight was 75.6 kDa. Monosaccharide composition analysis revealed that it was composed of rhamnose, arabinose, and galactose in a molar ratio of 1.0:14.9:10.4. Protein accounted for 1.7% of the AGP and was rich in hydroxyproline. On the basis of monosaccharide composition, partial acid hydrolysis, methylation analysis, ESI-MS, and NMR spectroscopy, LRGP3 was characterized as a highly branched polysaccharide with a backbone of (1 -> 3)-linked beta-D-galactopyranosyl residues, many of which were substituted at the O-6 position by galactosyl or arabinosyl groups. The branches ere composed of (1 -> 5)-linked arabinose, (1 -> 2)-linked arabinose, (1 -> 6)-linked galactose, (1 -> 3)-linked galactose, and (1 -> 2,4)-linked rhamnose, and the major nonreducing termini were alpha-L-arabinofuranosyl residues.