Primary Structural Characteristics and Antioxidant Activity of the Polysaccharide ZJP2 from Zizyphus jujuba cv. Muzao
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Abstract:
Crude polysaccharides (CPs) were extracted from Zizyphus jujuba cv. Muzao by water extraction, ethanol precipitation, deproteinization, and discoloration, and a purified polysaccharide fraction (ZJP2) was obtained by DEAE-52 ion-exchange chromatography and Sephadex G-100 column chromatography. The primary structure and antioxidant activity of both the CP and ZJP2 were analyzed and measured. The degree of esterification, total sugar content, uronic acid content, and molecular mass for CP were 38.40%, 71.95, 51.05%, and 59.1 kDa, respectively, and the corresponding values for ZJP2 were 47.10%, 91.29%, 58.27%, and 13.7 kDa, respectively. Chemical derivatization combined with gas chromatography analysis revealed that ZJP2 was composed of five monosaccharides; namely, rhamnose, arabinose, xylose, galactose, and galacturonic acid, with a molar ratio of 4.5:26.1:1.4:11.9:18.1. The iodine-potassium iodide experiment and infrared analysis verified that ZJP2 possessed a typical polysaccharide structure and probably had a large number of side-chains and branches. In the in vitro antioxidant study, the 2,2-diphenyl-1-picrylhydrazyl (DPPH?) and hydroxyl free-radical-scavenging rates of ZJP2 were 71.34% and 75.45%, respectively, at a sample concentration of 6.0 mg/mL, and were stronger than the rates of CP. Moreover, the scavenging abilities showed an apparent dose-response relationship with the sample concentration.
