Abstract:

After having been soaked in 80% ethanol, burdock roots were used for the extraction of water-soluble
polysaccharides by water extraction and ethanol precipitation. The optimal extraction conditions, as established by
one-factor-at-a-time and orthogonal array designs, were 1:25 (g/mL), 2.5 h and 85 ℃ for solid/solvent ratio, time and
temperature, respectively, and the extraction was repeated twice. Under the optimized conditions, the yield of water-soluble
polysaccharides from burdock roots was 8.43%. The crude polysaccharides were deproteinized by Sevag’s method and
characterized by UV and infrared spectroscopy. The purified products might be polysaccharides bound with peptide bonds.
In vitro antioxidant assays suggested that the polysaccharides had marked DPPH free radical scavenging activity, but weak
superoxide anion radical scavenging activity. In addition, they had no inhibitory effects on E. coli, S.aureus or B.subtilis.

Key words: ethanol-soaked roots of burdock (Arctium lappa L.), water-soluble polysaccharides, extraction, antioxidant activity, antibacterial effect