Structural characterization of polysaccharides from Zizyphus jujuba and evaluation of antioxidant activity

Fruit of Zizyphus jujuba Mill, a traditional Chinese herb widely consumed in Asian countries, has been reported to possess several vital biological activities. This study intends to develop an appropriate analytical method for isolation of polysaccharides from Z. jujuba fruits and evaluate their antioxidant activity. Initially, powdered Z. jujuba fruits were subjected to hot water extraction, followed by ethanol precipitation, deproteination, dialysis and fractionation in a DEAE-Sepharose CL-6B column. One neutral polysaccharide fraction (ZJPN) and 3 acidic polysaccharide fractions (ZJPa1, ZJPa2 and ZJPa3) were isolated with the average MW ranging from 40,566 to 129,518 Da. GC analysis revealed that 6 monosaccharides, namely, rhamnose, arabinose, xylose, mannose, glucose and galactose were present in polysaccharide fractions. The galacturonic acid content in polysaccharide fractions followed the order: ZJPa3 > ZJPa2 > ZJPa1 > ZJPN. All the 4 polysaccharide fractions were found to be more effective in scavenging superoxide anions than hydroxyl radicals, while acidic polysaccharides showed a more pronounced effect in chelating ferrous ion.