Cell wall polysaccharides of Chinese Wolfberry (Lycium barbarum): Part 2. Characterisation of arabinogalactan-proteins

Arabinogalactan-proteins (AGPs) were isolated from Wolfberry fruit (Lycium barbarum) and purified by anion-exchange chromatography and precipitation with Yariv reagent. Linkage and NMR analysis established the structure of Wolfberry AGP as typical of AGP reported from other sources. The data were consistent with a backbone of (1 → 3)-linked β-d-galactopyranosyl residues, many of which were substituted at O-6 with side chains of mainly 5-substituted α-l-arabinofuranosyl residues, terminated with α-(and β-)l-arabinofuranosyl, α-l-rhamnopyranosyl and β-d-glucopyranosyluronic acid residues. An unusual structural feature of the AGP was the occurrence of 4-substituted β-d-glucopyranosyluronic acid residues in the side chains. The AGP, which had a MW average of between 50 and 60 kDa, displayed heterogeneity with regard to both galactose/arabinose ratio and degree of branching. Protein accounted for ∼6% of the AGP and was rich in hydroxyproline. Evidence for an interaction between some of the AGP and hydrophobic moieties is presented.