Isolation, purification and structure of a new water-soluble polysaccharide from Zizyphus jujuba cv. Jinsixiaozao

A novel water-soluble polysaccharide (ZSP3c) was isolated from Zizyphus jujuba cv. Jinsixiaozao and its structure was investigated. ZSP3c was obtained by extraction with hot water followed by purification using DEAE-SepharoseCL-6B anion-exchange, SepharoseCL-6B and Sephadex G-200 column chromatography. It was eluted as a single symmetrical narrow peak on high-performance gel-permeation chromatography (HPGPC) and the average molecular weight (Mw) was estimated to be 1.4 × 105 Da. The ZSP3c was composed of l-rhamnose, d-arabinose and d-galactose in a molar ratio of 1:2:8. The structural features of ZSP3c were investigated by partial hydrolysis with acid, methylation analysis and NMR spectroscopy analysis. The results revealed that the main backbone chain of ZSP3c was (1 → 4)-d-galacturonopyranosyl residues interspersed with (1 → 2)-l-rhamnopyranosyl residues and (1 → 2,4)-l-rhamnopyranosyl residues. The neutral side chains of arabinofuranosyl residues and galactopyranosyl residues were attached to the backbone at the O-4 position of rhamnopyranosyl residues.