| Nostoc commune vauch is widely distributed and highly adaptable,and can grow in different environments,such as desert,grassland and half Gobi.Nostoc genera and other lower plants in different habitats can secrete a lot of polysaccharides to the extracellular environment under special environment such as desert and polar.They play a key role in maintaining cell integrity,preventing cardiovascular and cerebrovascular diseases,cancer,antioxidant and normal physiological functions.In this paper,the extraction technology of polysaccharides from Nostoc commune vauch was studied by single factor and response surface combination optimization method.Based on that,a kinetic model of crude polysaccharide extraction based on Fick second law was established.The crude polysaccharides extracted by two methods were purified by cellulose column DEAE-52 and gel column Sephadex G-100.Physicochemical properties,structural analysis and antioxidant properties of polysaccharides extracted from two methods and main eluent components were studied.The main results are as follows:(1)The optimum conditions for extracting crude polysaccharide from Nostoc commune vauch using hot water reflux method is liquid ratio of 1/50 g/mL,extraction temperature is 370.15 K,extraction time is 190 min,and the yield of polysaccharide is 10.43% under this condition.The extraction process conforms to the first-order kinetic model.For the polysaccharides extracted by using the optimal extraction conditions,the protein removal rate was 85.71% by Sevage method and the protein removal rate was 85.71%.After the deproteinized Nostoc commune vauch polysaccharide was purified by DEAE-52,five components including HNP1,HNP2,HNP3,HNP4 and HNP5 were obtained.The recoveries were 2.53%,29.34%,15.76%,4.38%,and 4.91 respectively.%,the polysaccharide HNP2 and HNP3 were separated by Sephadex G-100 column chromatography only one peak,initially determined as a single polysaccharide,the recovery were 83.1%,80.9%,are white floe.The physicochemical properties of the crude polysaccharides of Nostoc commune vauch were measured.The viscosity of the Nostoc commune vauch polysaccharides solution at the concentration of 0-1.0 mg/mL at room temperature increased with the increase of the sample concentration,which was L-substance.In 80 °C,the Nostoc commune vauch polysaccharides were treated with different heat treatment temperature and had better thermal stability;the extracts were illustrated by phenol-sulfuric acid reaction,iodine-potassium iodide reaction,ninhydrin reaction,Filin reaction,etc.It is a non-starch polysaccharide,protein-free,polypeptide or amino acid,which belongs to non-reducing sugar.The content of sulfated polysaccharide is 2.18% and uronic acid content is 33.41%,indicating that the polysaccharide of Nostoc commune vauch is an acidic polysaccharide.The weight average molecular weights(Mw)of HNP2 and HNP3 were 4.86×104 g/mol and 4.414×104 g/mol,respectively,and the number average molecular weights(Mn)were 2.272×104 g/mol and 1.807×104 g/mol,respectively.Mn was 2.144 and 2.443,respectively.The monosaccharide component of the two components after purification was determined,in which the monosaccharide molar ratio of HNP2 was rhamnose: mannose: glucose: galactose=0.63:0.57:6.3:2.5.The monosaccharide molar ratio of HNP3 was rhamnose: mannose: glucose: galactose=0.65:0.55:2.91:2.73.HNP2 and HNP3 may contain 1?2,1?2,6,1?3,1?3,6 and other types of glycosidic bonds through the periodate test;the backbone of HNP2 and HNP3 is ?-type by infrared spectroscopy.Pyranose.Under the scanning electron microscope,the surface morphology of the crude polysaccharides of Nostoc commune vauch was smooth and the edges were irregularly shaped;the surface of HNP2 was honeycombed and connected to each other;the surface of HNP3 was irregularly jagged.From the atomic force microscope image,the molecules of HNP2 and HNP3 can be obtained as thin ellipsoids.The enthalpy change of HNP2 is-161 J/g,and that of HNP3 is-226.1 J/g.(2)The optimum conditions for the ultrasonic extraction of Nostoc commune vauch polysaccharides were as follows: the ratio of material to liquid was 1/50 g/mL,the extraction temperature was 350.15 K,the power was 540 W,and the extraction time was 25 min.Under these conditions,the crude polysaccharide was obtained.The rate reached 13.07%.The ultrasonic extraction of Nostoc commune vauch polysaccharides conformed to the first-order kinetic model.For the polysaccharide extracted by using the best extraction conditions,the protein removal rate was 85.71% and 88.06%,respectively,by the Sevage method.The deproteinized Nostoc commune vauch polysaccharides were separated and purified by DEAE-52.Six components including UNP1,UNP2,UNP3,UNP4,UNP5 and UNP6 were obtained.The recoveries were 3.52%,3.36%,34.28%,and 17.54%,respectively.,5.86%,6.27%.Only one peak was separated from the UNP3 and UNP4 by Sephadex G-100 gel column chromatography.The initial determination was that it was a single polysaccharide.The recoveries were 86.4% and 82.7%,respectively,and all were white flocs.Determination of physicochemical properties of crude polysaccharides from Nostoc commune vauch.Among them,at room temperature,the viscosity of the solution of Nostoc commune vauch at a concentration of 0-1.0 mg/mL will increase with the increase of the sample concentration;within 80 °C,the Nostoc commune vauch polysaccharide has a good thermal stability.Through phenol-sulfuric acid reaction,iodine-potassium iodide reaction,ninhydrin reaction,Filin reaction,etc.,indicating that the extract is non-starch polysaccharides,no protein,peptides or amino acids,belonging to non-reducing sugar;ground Nostoc commune vauch polysaccharide polysaccharide sulfate content It was 2.04% and the uronic acid content was 35.12%,indicating that the crude polysaccharide of Nostoc commune vauch is an acidic polysaccharide.The weight average molecular weights(Mw)of UNP3 and UNP4 were 9.111×104 g/mol and 1.454×104 g/mol,and the number average molecular weights(Mn)were 3.341×104 g/mol and 4.432×104 g/mol,respectively.Mw/Mn was 2.724 and 3.281.The monosaccharide molar ratio of UNP3 was glucuronic acid: mannose: glucose: galactose=0.23:0.43:6.48:2.79.The monosaccharide molar ratio of UNP4 was rhamnose: arabinose: glucose=0.30:6.84:2.81.UNP3 and UNP4 were obtained as ?-glucopyranose by infrared spectroscopy.From the scanning electron microscopy image,it can be seen that the crude polysaccharide and UNP4 have a relatively obvious honeycomb;UNP3 is connected in a filamentous and flaky manner.The enthalpy change of UNP3 during thermal decomposition is-219.8 J/g,and the enthalpy change of UNP4 is-211.6 J/g.(3)The scavenging effect of superoxide anion radicals was poor in hot water extracts of Nostoc commune vauch polysaccharides,ultrasonically extracted Nostoc commune vauch polysaccharides,HNP2,HNP3,UNP3,and UNP4 at a concentration of 0-1.0 mg/mL;The scavenging effect of the components on hydroxyl radicals under the same concentration conditions is weaker than that of Vc.At 1.0 mg/mL,the DPPH· free radicals reached the maximum of 57.79%,61.80%,48.21%,40.21%,52.72% and 42.79%,respectively. |
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