Extraction,Purification,Physicochemical Properties And Antioxidant Activity Of Polysaccharide From Thesium Chinese Turcz

In order to further develop and utilize the resources of Thesium chinese Turcz,the extraction conditions of Thesium chinese Turcz polysaccharides（TPs）were studied using monofactorial and the response surface analysis.On this basis,purified fractions were isolated from TPs,they were studied on physicochemical characterization,preliminary analysis of structures,antioxidant activity.Main results are listed as follows:1.Three factors,extraction temperature,extraction time and solid-liquid ratio all had impact on the yield of TPs,among them,extract temperature had a significant influence on the yield of TPs.The optimum extraction conditions were liquid-raw ratio 1:20g/m L,extraction temperature 96.7℃,extracting time 2.5h,under optimum extraction conditios,the extraction yield of TPs was 17.19%.2.The total sugar content of TPs was 52.87±0.10%,and the ash content was7.62±0.12%,the water content was 6.02±0.11%.The pH value was 5.8±0.05,which was weakly acidic.The polysaccharide was soluble in water,insoluble in ethanol,acetone,chloroform and other organic solvents.The TPs showed a shear dilution state at low shear rate.When the shear rate was higher than 20 s^-1,the viscosity decreased gently with the increase of shear rate,showing the characteristics of Newtonian fluid.The TPs was more sensitive to temperature,but was lower sensitive to p H at room temperature.The elasticity modulus（G’）of TPs from different concentrations were higher than those of loss modulus（G’’）,which indicated that the gel properties of polysaccharide was more obvious.There exists the synergistic thickening effect between TPs with sodium alginate,carrageenan,linseed gum,gelatin.3.Three purified fractions,named by TPs-1,TPs-2,TPs-3 were obtained from TPs.The Fourier transform near-infrared（FT-IR）spectroscopy revealed that TPs and all three purified fractions contained characteristic absorptions of polysaccharides,they are all contain carboxyl and sulfated group.The results of determination of protein and UV scanning showed that purified fractions did not contain impurities such as protein,nucleic acid.According to HPLC analysis,TPs-1 was composed of mannose（24.15%）,rhamnose（3.57%）,glucose（32.23%）,galactose（18.19%）,xylose（5.27%）and arabinose（18.53%）;TPs-2 was composed of mannose（37.61%）,galactose（27.30%）,xylose（5.27%）,arabinose（29.82%）;TPs-3 was composed of mannose（7.64%）,rhamnose（2.39%）,glucuronic acid（0.86%）,galacturonic acid（3.51%）,glucose（9.38%）,galactose（40.48%）and arabinose（35.75%）.4.TPs had strong antioxidant activity in vitro.The results showed that TPs and its three purified fractions had obvious effect on scavenging free radicals of OH·and O₂·,meanwhile,it could scavenge DPPH free radicals.