Isolation and structural characterization of a polysaccharide from fruits of Zizyphus jujuba cv. Junzao

A water-soluble polysaccharide (ZP2a) was obtained by extraction with hot water followed by successive chromatographic purification using anion exchange and Sepharose CL-6B columns. A symmetrical narrow peak was obtained on high-performance gel permeation chromatography with an average molecular weight of 120,645 Da, which was named ZP2a. ZP2a is composed of rhamnose, arabinose, glucose and galactose in the molar ratio 1.3:1.7:0.3:1. Based on gas chromatographic, infrared spectral, methylation and NMR analyses, ZP2a was structurally characterized as 1,4-d-GalpA residues interspersed with 1,2-l-Rhap and 1,2,4-l-Rhap residues. The branches were composed of 1,5-l-Araf, 1,3,5-l-Araf, 1,3-l-Araf, 1,6-d-Galp, 1,4,6-d-Galp and 1,4-d-Glcp. The branches were attached to the backbone at the O-4 position of Rhap residues.