Extraction, Purification, Structural And Antioxidant Properties Of Water-soluble Polysaccharide From Dehulled Mung Bean

Mung bean is a traditional Chinese food and has been adopted for more than2,000yearssince ancient China. Mung bean is most renown for its nutritional components in which thestarch and protain compromise more that70%. Based on TCM, mung bean not only has thepharmacological function such as sterilization, detoxification, it also has a variety ofbiologivally anti-tumor, anti-bacterial as well as other biological effects. However, till now,the utilization of mung bean has been only used at the primary processing stage and it hasbeen mainly considered as a primary processing product, like the mung bean soup and themung bean cake. When it comes to the in-depth research work concering mung bean.However, research on bioactive substances in fresh green beans have seldom been reported,particularly on the properties of polysaccharides in green beans were very small.In this study, the extraction, isolation, purification, physical and chemical properties,structural analysis and in vitro antioxidant actiovity about polysaccharide extracting fromdehulled mung bean.During the experiments, the hot-water has been employed to extract the water-soluablepolysaccharride from dehulled mung bean. Before this, mung bean should been soaked in thewater for approximately12hours and then dried at the temperature of70℃. After this, thepowder of dehulled mung bean then has to be refluxed with80%ethanol for3h. On the nextstage, the powder should then be washed successively with petroleum ether, acetone, ethanol,95%ethanol and air-dried. After all these, the raw materials has been pretreatment and can beused to extract polysaccharide.Alcohol sedmentation has also been employed to precipitate. During the experiments,factors that affects the yield of polysaccharide have been studied as well, for instance, theextraction temperature, the extraction time, the ratio of water to raw materials as well asextraction times. Accordingly, response surface methodology (RSM) was employed tooptimize extraction conditions. The results indicated that the optimum conditions for MBPextraction were: water temperature of95.5°C, a ratio of water to raw material of21:1(V/m)and an extraction time of3h. Under these conditions, the yield of MBP reached4.32%. Afterdeproteination with Sevag reagent for4times, the content of protein was found to be thelowest which in turn indicated the4times is the most efficient way to remove or estimate thecontent of protein. After this, DEAE Cellulose-52column was employed to purify thepolysaccharide. At this stage,2frations can be acquired and the1st fraction has been collectedand then free-dried, named MBP. The yield of MBP was2.67%. The contents of total polysaccharide, protein as well as glucuronic acid and were62.14%,31.13%and10.51%. Theresults of UV scanning at190~400nm of MBP as well as the result of DEAE Cellulose-52column indicated the existence of protein even after deproteiniation for4times.According to the results of Iodine-potassium iodide reaction, Biuret reaget action,Fehlinngreagent reaction, Molish reaction and Erric chloride reagent, MBP was found to be anon-strch polysaccharide with a certain amount of protein. Also, there was no nucleic acidbut about10.51%uronic acid. Besides, the results of infrared spectrum analysis showed thatMBP contained characteristic absorption peak of polysaccharide structure. The scanningelectron microscope (SEM) provided qualitative indication of the surface structure of MBP.The result of Gel Permeation Chromatograophy (GPC) indicated the Mwof MBP was4020Da. The surface structure of MBP was found to be branch strip and porous. Themethodologies of HPLC and Ion Chromatography have also been empolyed to test thecontent of the monosaccharides and amino acids in MBP. The results indicated that MBP wasmainly consisted of Fucose, Arabniose, Galactose, Xylose, Mannos and Glucose in whichMannose occupised45.09%. And the molar ration of monosaccharide of MBP was1.07:1:2.93:3.38:7.59:0.70. Besides this, the amion acids contained in MBP was as follows:the protein in MBP was mainly consisted of Glutamic acid, Lysine, Arginine and AsparticAcid.In the study, the in vitro property of MBP has also been studied comparing with Vc. Theresults showed that MBP has great reducing power, scavenging of hydrogen peroxide andantioxidant activity. And the IC50of scavenging of hydrogen peroxide and antioxidant activitywere2.544mg/mL and0.163mg/mL respectively, which was much lower than Vc. Also, theability has increased by the increase of concentration.