Isolation and structural characterization of a polysaccharide FCAP1 from the fruit of Cornus officinalis

A water-soluble polysaccharide, FCAP1, was isolated from an alkaline extract from the fruits of Cornus officinalis. Its molecular weight was 34.5 kDa. Monosaccharide composition analysis revealed that it was composed of fucose, arabinose, xylose, mannose, glucose, and galactose in a molar ratio of 0.29:0.19:1.74:1:3.30:1.10. On the basis of partial acid hydrolysis and methylation analysis, FCAP1 was shown to be a highly branched polysaccharide with a backbone of β-(1→4)-linked-glucose partially substituted at the O-6 position with xylopyranose residues. The branches were composed of (1→3)-linked-Ara, (1→4)-linked-Man, (1→4,6)-linked-Man, (1→4)-linked-Glc, and (1→2)-linked-Gal. Arabinose, fucose, and galactose were located at the terminal of the branches. The structure was further elucidated by a specific enzymatic degradation with an endo-β-(1→4)-glucanase and MALDI-TOF-MS analysis. Oligosaccharides generated from FCAP1 indicated that FCAP1 contained XXXG-type and XXG-type xyloglucan fragments.