Ethanol Fractional Purification and Antioxidant Activities of Polysaccharides from Polygonum cuspidatum

The Polygonum cuspidatum polysaccharides were extracted with hot water and deposited by different gradient concentrations of ethanol (30%,50%,70%,90%) into four precipitation fractions,named PCP-30,PCP-50,PCP-70 and PCP-90. The yield of polysaccharide,the contents of sugar and uronic acid were determined,FTIR and UV spectroscopy were analyzed to determine their spectroscopy properties. The DPPH radical and reducing power were tested. The correlation of sugar content and uronic acid content with antioxidant activities were further studied. The results indicated that the composition contents of the four Polygonum cuspidatum polysaccharides were significantly different. PCP-70 showed the highest content of sugar (557.03 mg/g) and uronic acid (284.85 mg/g),and also exhibited the highest antioxidant activity in DPPH radical-scavenging test and ferric reducing power test. Four different polysaccharide fractions all had the typical groups of polysaccharides by infrared analysis,and they had almost no difference in the UV scanning spectra. The results of correlation coefficients showed that the sugar content and uronic acid content correlated highly with DPPH radical scavenging and ferric reducing power. Therefore 70% ethanol was considered appropriate for precipitating Polygonum cuspidatum polysaccharide,and the PCP-70 showed high antioxidant activities.