Study On Extraction Of Lentinan And Modification Of The Molecular Structure

Lentinan had attainded so much more attentions due to many kinds of biological activities such asantitumor, antivirus, immune regulation, antioxidation and so on. And it had no toxic side effects toother cells of the human body, what’s more, the polysaccharides modified by sulfation could have anew anti-HIV activity. In order to improve the yield and purity of lentinan polysaccharides, this paperaims to develop a fast, easy Lentinan extraction process, and to ensure that its biological activity is notdestroyed. In this thesis, mushroom fruiting bodies were made as raw material and the advantages anddisadvantages of different extraction methods and its effects on the physical and chemical properties oflentinan were discussed. And a new joint extraction method was established.The effects on extraction yield, antioxidant activity, molecular shape, molecular weight,monosaccharide composition and other aspects by different methods were studyed, the main researchcontents and results are as follows:1. Four methods (reflux hot water, ultrasonic, microwave and high-temperature hot water) wereperformed to extract lentinan polysaccharides, the study found that the yield of extraction by hightemperature hot water maximum reached14.25%, which is1.71times the ultrasonic extraction, andhigher than hot water extraction and microwave extraction by27.01%,42.07%. Although the yield ofextraction by high temperature hot water was maximum, but due to the high temperature, the structureof polysaccharides was destroyed partly, and the antioxidant activity in vitro was lower. However, theantioxidant activity of polysaccharides extracted by ultrasonic was preferably, there was less damage tothe molecular structure.2. The optimal conditions of ultrasonic-high-temperautre methods are the first step of ultrasonictemperature62℃, time50min, power of640W, the second step of high-temperature hot waterextraction120℃, time40min. The extraction yield reached15.57%, which was1.87and1.39times ofthat of the polysaccharides prepared by ultrasonic and traditional water extraction. The wholeextraction process requires only90min, which is half time of the traditional water extraction time (3h)and greatly improves the extraction efficiency of lentinan.3. The products prepared by ultrasonic wave and high-temperature hot water were performed forchemical composition analysis, the results showed that the polysaccharides extracted by high-temperature extraction had higher purity of91.98%, a uniform and smaller molecular weight of3.7×105Da, while ultrasonic extraction polysaccharides have two peaks.. A red shift phenomenonwas observed when conducted Congo red experiments, and the polysaccharides extracted byultrasound performed red shift phenomenon significantly, indicating that it had complete triple helixstructure. And the results were confirmed by a scanning electron microscope.4. The polysaccharides prepared by high-temperature modified by different physical andchemical methods, the results show that the antioxidant capacity of sulfated polysaccharides has beensignificantly improved. The reducing power of crude polysaccharides, ultrasonic modifiedpolyacccharides, sulfation modified polysaccharides and ultrasonic-sulfation modified polysaccharideswere0.11,0.20,0.50and0.54at the concentration of1mg/mL.Their IC50value of DPPH radicalscavenging capacity were3.62,2.25,0.81and0.95mg/mL, respectively. At the concentration of200μg/mL, their ORAC values were195.8,416.6,471.3,782.1μmolTrolox/g, respectively. And thedegree of substitution (DS) of ultrasonic-sulfation modified polysaccharides was3.23times biggerthan that of the sulfated polysaccharide. Although the antioxidant activity of sulfated polysaccharidehas been greatly improved, there was a great degradation of polysaccharides. The molecular weightwas less than10000Da. However, the treated polysaccharides still have absorption characteristic ofpolysaccharides by IR spectrum.