Kinetic modeling of microwave extraction of polysaccharides from Astragalus membranaceus

Abstract

Astragalus is one of the traditional Chinese herbs used for both medicine and food, and the extraction of polysaccharides from Astragalus is popular for its pharmacological activities. In this present study, a new theoretical kinetic model for microwave extraction of polysaccharides was developed by combining Fick's law with microwave electromagnetic field enhancement diffusion theory. Based on fitting to experimental data, a semi-empirical kinetic model was then established using multiple nonlinear regression, achieving a high determination coefficient (R2) of 0.9223. The semi-empirical model was used to provide more insights in microwave extraction and mass transfer mechanism of Astragalus polysaccharides. Astragalus cellular structures as affected by microwave extraction were also analyzed by scanning electron microscopy, revealing that the extraction was mainly due to the action of microwave-induced pressure in Astragalus cells, causing destruction of Astragalus cellular structure. Practical applications Astragalus is a traditional Chinese herb that can be used for both medicine and food. Extraction of polysaccharides from Astragalus is popular as Astragalus polysaccharide (APS) has high biological activity for reducing blood sugar, anti-oxidation, anti-virus, anti-tumor, anti-inflammatory, and enhancing immunity. Therefore, optimizing the extraction process plays an important role in enhancing extraction rate. In this study, kinetic models for microwave extraction of APS were established, scanning electron micrograph revealed that microwave treatment could generate Astragalus intracellular pressure, which caused destruction of the Astragalus cellular structure, thus improving the extraction efficiency. Results indicated that higher degree of Astragalus cellular structure damaged by microwave would lead to higher extraction rate of polysaccharide. The study would thus provide guidance for improving the microwave extraction process of polysaccharides from Astragalus for the industry.