Study On Purification,Modification And Physicochemical Properties Of Polysaccharides From Polygonatum Sibiricum

Using Polygonatum sibiricum(PS)as raw material,ultrasound-assisted extraction was utilized to extract polysaccharides from Polygonatum sibiricum(PSP),and the optimal extraction conditions were explored.The polysaccharide was separated and purified by column chromatography to obtain the component PSP1-A.The UV-Vis spectroscopy,molecular weight,scanning electron microscopy,FT-IR spectra,X-ray diffraction and monosaccharide compositions of PSP1-A were analyzed.The carboxymethylated and sulfated derivatives of pure polysaccharides were prepared as SPSP1-A and CPSP1-A,and the antioxidant activities,the inhibitory activity against a-glucosidase and a-amylase and the repair effect of the DNA damage were compared.The result is as follows:(1)Response surface method was used to optimize conditions of the ultrasonic extraction process,the optimal conditions were as follows:ultrasonic power of 180W,extraction time of 62min,liquid to material ratio 21:1.Under this condition,the yield of PSP was 18.65%±0.04%.Ultrasonic treatment could damage plant cell and the polysaccharides are dissolved to increase the extraction rate.(2)By comparing the four methods of protein removal,such as hydrochloric acid method,enzymatic method,Sevage method and trichloroacetic acid method(TCA method),the results showed that hydrochloric acid method deproteinized worst;Enzymatic method has low loss of polysaccharides,but there was a risk of introducing foreign proteins;the Sevage method was cumbersome with massive losses of polysaccharide,although achieved a high protein removal rate;the TCA method has the best effect with deproteinization rate of 96.82%and polysaccharide loss rate of 26.81%.The optimal process conditions of TCA method were as follows:sample ratio of 4:1,TCA content of 3%,and shaking treatment time of 25 min.After purified by DEAE-52 cellulose chromatography and Sephadex G-200,the component PSP1-A was obtained.(3)The physicochemical properties of the polysaccharide component PSP1-A were analysed.The UV scanning confirmed that PSP 1-A didn't contain protein and nucleic acid;PSP 1-A was a homogeneous polysaccharide with the average molecular weight of 12.83 kDa.The electron microscopic observation showed that PSP 1-A was a strip-like network structure with strong intermolecular force.The FT-IR results showed that PSP1-A contained typical characteristic absorption peaks of polysaccharides,of which ?-type pyranoside might be the dominating glycosidic bond;The XRD patterns of PSP1-A suggested that they were amorphous powder with low crystallinity;the monosaccharide composition of PSP 1-A was mannose,galactose and glucose,and the molar ratio is 15.06:65.40:19.53.(4)Sulfated polysaccharides(SPSP1-A)with a degree of substitution of 1.44 and the carboxymethylated polysaccharides C1PSP1-A,C2PSP1-A and C3PSPI-A(the degrees of substitution were 0.21,0.37 and 0.49,respectively)were obtained by two chemical structural modifications.The results of antioxidant activity showed that PSP1-A had different scavenging abilities on DPPH radical,ABTS radical and hydroxyl radical,and the reducing power was weak.The antioxidant ability of SPSP1-A was obviously improved.CPSP1-A decreased the scavenging power of ABTS radical,and the ability to scavenge two other free radicals were enhanced,and the antioxidant capacity increased with the increase of substitution degree.In addition,the results of a-glucosidase and a-amylase activity inhibition experiments showed that both polysaccharide structure modification methods can increase the inhibition level of enzyme activity.Compared with the native polysaccharide,the CPSP1-A with highest DS exhibited the highest antioxidant and inhibitory activities.Difterent doses of PSP1-A and SPSP1-A had significant repair effects on DN A-damaged 293 cells,and there was a dose-dependent relationship.At the same dose,the repair effect of PSP1-A was stronger than that of SPSP1-A.