Extraction,Purification,Structure Characterization And Application Of Polysaccharide From Sweet Potato Leaves

Sweet potato leaves,are the leaves of the sweet potato vine,which is a sweet potato plant in the Convolvulaceae family.Although sweet potato has long been regarded as a long-lived food,sweet potato leaves are discarded or used as fodder,leading to waste of resources.In this paper,sweet potato leaves are used as raw materials,the traditional hot water extraction method and ultrasonic-assisted enzymatic method are used to extract sweet potato leaf polysaccharides,and the appropriate extraction method is selected by comparing the yield of polysaccharides.The separation,purification,structure characterization,antioxidant activity and solid beverage preparation of sweet potato leaf crude polysaccharides prepared by ultrasound-assisted enzymatic method were also studied.The following are the main findings:1.Through the optimization of single factor and response surface experiments,the best process for hot water extraction of sweet potato leaf polysaccharides was determined:extraction time 180min,extraction temperature 95?,liquid-to-material ratio 50:1(m L/g),under these conditions The yield of polysaccharides was 4.82%.2.Through single factor experiment design method and response surface method,the best technology of ultrasonic-assisted enzymatic extraction of sweet potato leaf polysaccharides was determined:cellulase dosage 1.5%,ultrasonic power 210W,ultrasonic time In 32 minutes,the yield of polysaccharides reached 8.16%under these conditions.Compared with the hot water extraction method,the yield of sweet potato leaf polysaccharides is greatly improved,which is called SPLU.3.The sweet potato leaf crude polysaccharide(SPLU)extracted by ultrasound assisted enzymatic method is separated and purified by DEAE-52 cellulose ion exchange column and Sephadex G-100 gel column after removing protein and pigment,after dialysis,concentration and freeze-drying,the purified polysaccharide is obtained.SPL-?,SPL-?.4.Through Gel Chromatography(GPC),Gas Chromatography(GC),Scanning Electron Microscope(SEM),Ultraviolet Spectroscopy(UV),Fourier Transform Infrared Spectroscopy(FTIR)and other methods to determine its monosaccharide composition,relative molecular mass and appearance,The structure and other aspects have been studied.Liquid chromatography and gas chromatography analysis showed that the weight-average relative molecular masses of the two purified polysaccharides were 4.48×10~4 and 5.19×10~4,respectively.Among them,SPL-?is composed of arabinose,mannose,fructose,glucose and galacturonic acid with a molar ratio of0.533:3.675:0.116:0.425:0.326.SPL-II is composed of arabinose,mannose,glucose and galacturonic acidwith a molar ratio of 0.209:1.081:0.172:0.242.The appearance of the polysaccharide was observed with a scanning electron microscope.Under the condition of 1000 times magnification,it was found that the surface had different levels and unevenness.Under the condition of 5000 times magnification,it is found that the surface of the polysaccharide is flat,dense in structure,and smooth and thin.The infrared spectrum of the leaves showed that the two groups of polysaccharides separated by chromatography have the characteristics of typical polysaccharide absorption peaks,and the sugar chain structure is polypyranose.5.The antioxidant capacity of sweet potato leaf polysaccharides was tested.The test results show that the scavenging ability and reducing ability of SPL-I on DPPH free radicals and hydroxyl free radicals are better than SPL-?and SPLU.When the concentration of SPL-I of sweet potato leaf polysaccharide was 1.0 mg/m L,the scavenging activity of SPL-I on DPPH free radicals and hydroxyl free radicals was close to VC,which were 79.32%and 61.22%,respectively,but the reduction effect was significantly lower than that of VC.The free radical scavenging ability of sweet potato leaf polysaccharide and VC is as follows:VC>SPL-?>SPL-?>SPLU6.Using sweet potato leaf polysaccharides as the main raw material,a new type of solid beverage has been developed.With sensory evaluation as an indicator,the formula of sweet potato leaf polysaccharide solid beverage was optimized through single factor method and response surface method.The results showed that the addition amount of sweet potato leaf polysaccharide was 0.25g,the addition amount of sugar alcohol was 1.50g,the addition amount of pectin was 0.15g,and the addition amount of citric acid was 0.03g.Under these conditions,experimental verification was carried out,and the calculated average sensory score was 9.46,reaching 97.12%of the predicted value.The sensory index analysis of the sweet potato leaf polysaccharide solid beverage and the analysis of the national solid beverage standard requirements were carried out.The developed solid beverage has a sweet taste,is suitable for all ages,and has certain development prospects.