Structural characterization and antioxidant activity of polysaccharides extracted from jujube using subcritical water

Polysaccharides were extracted from jujube fruit using an efficient, optimized subcritical water extraction process. A maximum crude polysaccharide yield of 7.9% was obtained at an extraction temperature of 140 degrees C and a time of 60 min. The crude polysaccharides extracted under these conditions were purified. Three polysaccharide fractions, ZP1, ZP2 and ZP3, were obtained and their structures were investigated. The three fractions were mainly composed of arabinose, galactose, glucose, mannose, rhamnose, and galacturonic acid. ZP3 was further investigated using methylation and NMR spectroscopy, and ZP3 comprised a main chain of (1 -> 4)-alpha-D-GalAp, (1 -> 2,4)-alpha-L-Rhap, with a (1 -> 4,6)-alpha-D-Galp branch. Assays of antioxidant activity showed that ZP3 exhibited a remarkable DPPH capacity and moderate hydroxyl radical scavenging ability, suggesting that it has potential applications as a natural antioxidant in foods and pharmaceuticals.