Structural characterization and in vitro antitumor activity of polysaccharides from Zizyphus jujuba cv. Muzao

Abstract

Water-soluble polysaccharides were extracted from the Zizyphus jujuba cv. Muzao using an ultrasonically assisted extraction method and fractionated by DEAE-Sepharose Fast Flow ion-exchange chromatography. The relevant fractions (HJP1 and HJP3) were subjected to structural analysis by using characterization techniques such as acid hydrolysis, partial acid hydrolysis, periodate oxidation-Smith degradation, methylation, FT-IR spectral and NMR spectral analysis. Both HJP1 and HJP3 were determined to be acidic polysaccharides with a molecular weight of 6.762 × 10⁴ Da and 2.936 × 10⁴ Da, respectively, comprising of mannose, rhamnose, galactose, galacturonic acid, glucose and arabinose. The demonstrated data (monosaccharide composition, methylation analysis and ¹³C NMR spectrum) points to the presence of type I rhamnogalacturonan (containing arabinogalactan/arabinan side chains) domains and typical pectic polysaccharides, with homogalacturonan (methyl and acetyl esterified). The results from in vitro antitumor studies indicate that both HJP1 and HJP3 could inhibit the growth of human HepG2 cells and HJP3 had stronger cytotoxicity against HepG2 cells than HJP1, suggesting that these polysaccharides could potentially be used in liver cancer prevention and treatment.