Extraction,Modification And Immunity Activity Of Polysaccharide From Nitraria Tangutorun Bobr.

Nitraria tangutorun Bobr.belongs to the Nitraria Zygophyllceae and it’s fruit has been used both as food and medicine.The fruit of N.tangutorun Bobr.is rich in polysaccharides,the studies show that polysaccharides from N.tangutorun Bobr.fruit has the biological activity of immune regulation,antioxidation and so on,which has great value for development and utilization.This study aimed to optimize the polysaccharide extraction and decolorization processes,modify the polysaccharides by carboxymethylation,characterize the chemical structures of N.tangutorun Bobr polysaccharides before and after carboxymethylation,and explore the antioxidation and immune activities of the polysaccharides,in order to develop and utilize N.tangutorun Bobr.polysaccharides.The main results were as follows:1.Optimizing the extraction process of plant polysaccharide can reduce the waste of resources and energy consumption.Therefore,based on the single factor experiments,the hot water extraction and enzyme-assisted extraction of polysaccharides from N.tangutorun fruits were optimized using response surface methodology.For the hot water extraction technology,an extraction yield of 39.67± 0.02%could be achieved under the optimal conditions that extraction temperature of 79℃,extraction time of 1.5 h and solid-liquid ratio of 1:15.For the enzyme-assisted extraction technology,an extraction yield of 39.57 ± 0.11%could be achieved under the optimal conditions that enzyme dosage of 2.5%,temperature of 79℃,pH of 3,extraction time of 58 min.Enzyme-assisted extraction of polysaccharides from N.tangutorun reduced the extraction time,extraction temperature and number of extractions,and greatly reduced energy consumption in the extraction process.2.The crude polysaccharide extracted from plant raw materials usually has a darker color,which severely limits the application of plant polysaccharides in the food and pharmaceutical industries.In order to effectively solve this problem,in this experiment,macroporous resin adsorption method was used to decolorize the polysaccharide solution from N.tangutorun,and the decolorization process was optimized.Based on static adsorption experiments,the HPD-100A macroporous resin was selected from 10 macroporous resins as the decolorization resin,and the effects of pH on the decoloration,recovery of polysaccharides,and deproteinization of macroporous resin were investigated;dynamic adsorption experiments were used to investigate the effects of sample flow rate and sample concentration on the decolorization and deproteinization of macroporous resin.The optimized decolorization conditions were as follows:the polysaccharide concentration was 1.04 mg/mL,the pH was 5,and the sample flow rate was 1.5 BV/h,using HPD-100A macroporous resin as decoloring resin.Under this condition,the decolorization rate of crude polysaccharide was 74.78%,the deproteination rate was 70.96%,and the recovery rate of polysaccharide was 86.31%.3.At present,polysaccharides are structurally modified by multiple chemical methods.In this study,a carboxymethylated polysaccharide with a degree of substitution of 0.36 was prepared by the sodium hydroxide-chloroacetic acid method.The yield of carboxymethylated polysaccharide was 51.38%.The protein,uronic acid and total sugar content of N.tangutorun polysaccharides(NTP)and carboxymethylated N.tangutorun polysaccharides(CMNTP)were estimated.The monosaccharide composition of NTP and CMNTP were analyzed by HPLC pre-column derivatization.The results showed that both NTP and CMNTP were composed of mannose,glucuronic acid,galacturonic acid,rhamnose,glucose,galactose,and arabinose.The HPGPC method was used to determine the molecular weight of NTP and CMNTP.The molecular weight of NTP ranged from 74359 Da to 438665 Da,and the molecular weight range of CMNTP was 11459 Da to 80385 Da.Infrared spectrum analysis showed that NTP and CMNTP had characteristic absorption peaks of polysaccharides.After carboxymethyl modification,characteristic absorption of carboxymethyl groups appeared in the infrared spectra.The Congo Red experimental results showed that the NTP and CMNTP both had a triple helix structure.4.The antioxidant activities of NTP and CMNTP in vitro were determined using hydroxyl radical,superoxide anion radical and DPPH free radical system.The results showed that the NTP and CMNTP had different scavenging effects on hydroxyl radicals,superoxide anion radical and DPPH radicals.After carboxymethylation,the ability of scavenging hydroxyl radicals and superoxide anions of N.tangutorun polysaccharides were improved significantly.5.In this study,cyclophosphamide-induced mouse immune suppression model was used to study the immune regulatory effects of NTP and CMNTP on immunity in immunosuppressed mice.The results showed that NTP and CMNTP could significantly increase the thymic index and spleen index in cyclophosphamide-induced immune-suppressed mice(p<0.05),and significantly increase IFN-γ and IL-4 levels in serum of immunosuppressed mice(p<0.05),improve Thl/Th2 immune imbalance,increase the length of intestinal villus,reduce the decline of V/C value,and promote the secretion of SIgA in mice small intestine.And after the carboxymethylation,the immune regulatory effects of N.tangutorun polysaccharides was improved.