Investigation Of Kinetics And Mechanism Of Microwave Induced Pressure For Polysaccharide Extraction From Astragalus

Astragalus is one of the traditional Chinese herbs that can be used for both medicine and food,and is widely used in clinical practice.The research of polysaccharide from Astragalus has become a research hotspot all over the world due to its high biological activity,including enhancing immune system function,anti-inflammatory,anti-virus,anti-tumor,anti-oxidation,anti-aging and hypoglycemic effects.The advantages of microwave extraction are significantly improving the extraction efficiency,saving time and energy,and simple operation.The topic of this research was to extract polysaccharide from Astragalus,and the specific aims were:optimizing the microwave extraction processing by means of single factor and response surface methods;constructing extraction kinetics model based on Fick’s law and enhanced diffusion theory of electromagnetic field;researching the properties of Astragalus polysaccharides based on the optimal extraction technology;combining scanning electron micrographs to reveal the formation mechanism of microwave induced pressure field.The results were shown as below:(1)Microwave extraction of Astragalus polysaccharide process optimization.The single factor experimental method and the center combined experimental design method were used to study the polysaccharide extraction rate by selecting the ratio of liquid to material,microwave power,microwave time,and microwave temperature as experimental factors.The microwave extraction of Astragalus polysaccharide process was optimized and validated to obtain optimal processing parameters:the ratio of liquid to material was 9.85 mL/g,the microwave power was600 W,the microwave time was 23.03 min,and the microwave temperature was 96~oC,respectively.Therefore,the extraction yield of polysaccharide was up to 5.72%(Astragalus basis weight).(2)Microwave extraction kinetics model study.According to Fick’s law and enhanced diffusion theory of electromagnetic field,a theoretical model of microwave extraction kinetics was established.Moreover,a semi-empirical and semi-theory extraction kinetics model for microwave extraction was finally established by using the multiple nonlinear regression theory.The model was verified to have a fitness of 0.8504,indicating that the model was instructive.(3)Chemical properties analysis of microwave extracted Astragalus polysaccharides.The results showed that Astragalus crude polysaccharides had a molecular weight(Mw)of 8732 Da,a carbohydrate content of 87.10%,a protein content of 6.88%,a total polyphenol content of5.26%,a sulfate group content of 4.98%,and a uronic acid content of 18.51%,respectively.Furthermore,monosaccharide components of rhamnose,arabinose,mannose,glucose,and galactose were identified in Astragalus polysaccharides by employing Gas Chromatographic analysis,and their molar ratio was 2.12:6.43:7.00:78.62:5.83.(4)Microwave extraction mechanism research.A microwave induced pressure extraction method was proposed and the changes in the internal pressure of the microwave extraction system were analyzed.The linear correlation(R~2)between extraction system pressure and the extraction rate of polysaccharide from Astragalus was 0.9636 which directly revealed the extraction mechanism based on microwave induced pressure field.Additionally,the relationship between the pressure and the damage of the material structure was analyzed by scanning electron microscopy,which indirectly revealed the extraction mechanism based on the microwave-induced pressure field.Research conclusions:A semi-empirical and semi-theory microwave extraction kinetics model was constructed both practically and theoretically,and the mechanism based on microwave induced pressure extraction has been further explored.