Abstract: The polysaccharides of Eclipta alba were extracted by immersing in the mixture of water and methanol,and were then purified using silica gel column chromatography and medium-pressure liquid chromatography.The main monosaccharides of the polysaccharides were found to be glucose and fructose based on thin layer chromatography (TLC) analysis.The polysaccharides of E.alba showed good activities in the assays of total reducing power,total antioxidant power and FRAP antioxidant power.The polysaccharides can scavenge hydroxyl radical and DPPH radical effectively,with (12.33~56.81)% scavenging rates of the hydroxyl radical at the concentration of 1.5 mg/mL,and (17.88~84.47)% scavenging rates of the DPPH radical for the crude polysaccharides at the concentration of 1 mg/mL,and (18.64~91.35)% scavenging rates of the DPPH radical for the refined polysaccharides at the concentration of 5 mg/mL,respectively.Small polarity polysaccharides showed stronger antioxidant activities than large polarity polysaccharides with the antioxidant activities up to 11 times of the latter.The crude polysaccharides showed better antioxidant activities than relevant refined polysaccharides,which indicated that different polysaccharides of E.alba probably existed synergetic antioxidant effect.

Key words: Eclipta alba, polysaccharides, antioxidant activity, thin layer chromatography