Structural Characteristics and Antioxidant Activity of Two Novel Water-Soluble Polysaccharides from Acanthopanax leucorrhizus

Two novel water-soluble polysaccharides (ALPS-21 and ALPS-32) were isolated and purified from Acanthopanax leucorrhizus. Their structures were investigated by HPGPC, HPLC, IR, methylation and NMR, and the antioxidant activity was evaluated in vitro by 1,1-diphenyl-2-picrylhydrazyl radical (DPPH^·), hydroxyl radical (HO^·), and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS^·+) assay. Results showed that ALPS-21 was a 4.36 kDa neutral heteropolysaccharide composed of glucose, galactose, mannose, xylose in a ratio of 3.5:1.3:0.9:2.1, whereas ALPS-32 was a 5.78 kDa acidic heteropolysaccharide composed of glucose, galactose, mannose, and glucopyranuronic acid in a ratio of 4.5:1.3:1.1:1.0. Moreover, ALPS-21 and ALPS-32 can scavenge DPPH^·, HO^·, and ABTS^·+ in a dose-dependent manner, suggesting that ALPS-21 and ALPS-32 may be promising as a potential natural antioxidant.