| Polysaccharides and selenium have preventive and therapeutic effects on many diseases.In recent years,researches on the activity of polysaccharides and selenium have been conducted in depth.However,polysaccharides and selenium are organically combined into selenium polysaccharides,which study at native and abroad is still in its infancy.Selenium polysaccharides in selenium-enriched tea have attracted increasing attention due to their high absorption rate,safety and non-toxicity.This study focused on Se-polysaccharides binding morphology analysis of several selenium-enriched tea polysaccharides obtained by Se-enriched methods,and compared the activity and structure of several selenium polysaccharides.The main contents are as follows:1)The effects of different precipitants and alcohol concentration on the extraction and activity of tea polysaccharides were investigated.The results showed that ethanol precipitation had the best effect,and the 50%ethanol concentration had the best polysaccharide activity.The correlation analysis of the components and activities of the crude polysaccharides showed that the DPPH free radical scavenging activity was significantly correlated with the contents of polyphenols and uronic acid in the crude polysaccharides,and positively correlated with tea polyphenols.The?-glucosidase activity was significantly correlated with the protein and uronic acid content in the crude polysaccharide.2)The effects of different extraction processes on the composition and activity of tea polysaccharides were studied,including water extraction?WE?,enzymatic extraction?EE?,microwave?MAE?and ultrasonic?UAE?.The polysaccharide samples obtained from the four extraction processes have the same monosaccharide composition and different molar ratios of monosaccharides.In addition,EE had a low polysaccharide protein or nucleic acid content and a high pyranose content.The four extraction processes had different solid-state structural features in appearance.The activity of tea polysaccharides obtained from the four extraction processes were also significantly different.The scavenging effect on ABTS free radicals was:WE>UAE>MAE>EE;the scavenging effect on superoxide anion radicals was:WE>MAE>UAE>EE.The experimental results show that WE should be used to extract tea polysaccharides and selenium-enriched tea polysaccharides needed for subsequent experiments.3)Several crude tea polysaccharides and selenium-enriched polysaccharides were extracted by water extraction and alcohol precipitation,and then further purified on anion exchange agarose gel column DEAE Sepharose Fast Flow?2.5cm×60cm?eluted with PH=6.0 0.02mol/L NaCl phosphate buffer solution,and after freeze-drying,finally polysaccharide samples of Tps1,Ase-tps1,and Nse-tps1 were obtained.In addition,chemically synthesized tea polysaccharide?Cse-tps1?was prepared by chemical synthesis of sodium selenite modified via Tps1.4)Chemical analysis of polysaccharides revealed that all four polysaccharides were acidic polysaccharides,and Cse-tps1 had the highest selenium content.The selenium-polysaccharide binding morphology in selenium polysaccharides was characterized by UV,IR and Raman spectra.The results showed that Cse-tps1 was mainly composed of?VasC-O-Se?and O-H-Se bonds with polysaccharides.There may be a small amount of bound selenate polysaccharide structure in Ase-tps1,but most of them exist as free Se-H bonds.Nse-tps1 mainly exists in the form of Se-H bond in the free form.5)The DPPH scavenging activity of free radicals in vitro was used to evaluate the antioxidant capacity of polysaccharides.Studies have shown that ordinary and several selenium-enriched tea polysaccharides have scavenging effects on DPPH free radicals,and the activity of scavenging free radicals of tease polysaccharide?Cse-tps1?modified by sodium selenite was obviously stronger than that of ordinary tea polysaccharide?Tps1?,and there was a certain synergistic effect between selenium and polysaccharides in the activity test of selenium-enriched tea polysaccharides.The in vitro digestive enzyme assay was used to analyze and evaluate the hypoglycemic ability of polysaccharides.The results showed that ordinary and several selenium-enriched tea polysaccharides all had inhibitory effects on?-glucosidase activity,and tea polysaccharides chemically modified with sodium selenite?Cse-tps1?scavenging free radical activity was significantly stronger than that of ordinary tea polysaccharide?Tps1?,but the inhibitory activity of selenium polysaccharides?-glucosidase was significantly correlated with acid sugar content in the activity test of selenium-enriched polysaccharides.6)The ion-chromatography,Congo red,iodine-potassium iodide experiment and nuclear magnetic resonance were used to study the solution behavior and chemical structure of Tps1,Ase-tps1,and Cse-tps1.The morphology,crystallinity and thermal properties of Se-polysaccharides were studied by scanning electron microscopy?SEM?,X-ray diffraction?XRD?and differential scanning calorimetry?DSC?.Ion chromatographic results showed that Tps1 and Ase-tps1 contained the same monosaccharide composition,rhamnose,arabinose,galactose,glucose,xylose,mannose,fructose,and galacturonic acid,respectively.However,2.45 percent of Glucosamine was contained in Cse-tps1,and only 0.27 percent of galacturonic acid was at the lowest.The results of Congo red test showed that there were a rigid conformation between CSe-tps1 and Tps1,but there were still a difference in the conformational conversion mechanism between selenium polysaccharides and common polysaccharide in NaOH solution.The reason may be due to the effect of selenium on the polysaccharides leading to the breakage of intermolecular or intramolecular hydrogen bonds of polysaccharides.The significant difference between the apparent morphologies of Cse-tps1,Ase-tps1,and Tps1 may be due to the interaction between selenium and polysaccharides that alters the intermolecular interactions and the role of van der Waals forces.X-ray diffraction revealed that Ase-tps1 may have a smaller particle size microcrystalline system,and Cse-tps1 was more prone to single crystal morphology than the other two polysaccharides.Differential Scanning Calorimetry revealed that Ase-tps1 and Cse-tps1 produced new compounds during biological and chemical synthesis.13C NMR spectroscopy showed that the selenium oxygen bond in Cse-tps1 was on the O-6 substituted carbon.In addition,the C-6 peak was still present in Cse-tps1,indicating the remaining OH groups at the C-2 and C-3 positions were not selenized.The Ase-tps1 was mainly a?-1,4-linked glucose by analyzed 1D NMR and 2D NMR techniques. |
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