Environmentally Responsive Switchable Hydrophilic Solvent Extraction And Separation Of Plant Polysaccharides

In recent years,switchable solvents have been more widely used in green chemistry.Due to the property of hydrophilic conversion between switchable solvents,temperature-and CO₂-responsive switchable hydrophilic solvents were introduced in this experiment,which are considered to be the best alternatives to other organic or volatile solvents and are receiving increasing attention.In this thesis,we used temperature-responsive switchable hydrophilic solvents and CO₂-responsive switchable hydrophilic solvents to extract and separate polysaccharides from Lycium barbarum and Polygonatum sibiricum by solid-liquid extraction and to investigate the mechanism of their extraction.The main elements are as follows:（1）In the experimental study,12 temperature-responsive deep eutectic solvents（DES）were used to extract Lycium barbarum polysaccharide（LBP）.At this point,the polysaccharide is dissolved in the hydrophilic eutectic solvent,forming a homogeneous system with the solvent,which is recovered by temperature response,and the deep eutectic solvent is in a hydrophobic state at this point,allowing it to be separated from water for recovery.The solid-liquid ratio,DES content,extraction temperature and extraction time,which are the influencing factors of solid-liquid extraction,were investigated.The stability of LBP was assessed by studying its structure,extraction properties and extractant activity.Next,the DES was calculated to be recyclable by recovering this hydrophilic conversion solvent in aqueous solution.The final experiments showed that the extraction of LBP by the deep eutectic solvent was carried out in five cycles and after the fifth cycle,the extraction of LBP still reached 427 mg/g according to the optimum experimental conditions,while the recovery of the deep eutectic solvent remained at 80.2%.（2）In the experimental study,a CO₂-responsive switchable amine solvent was used to extract Polygonatum sibiricum polysaccharide（PSP）,using a CO₂ switch for the hydrophilic and hydrophobic conversion.The amine solution chosen was hydrophobic at room temperature and was passed through a continuous flux of CO₂ gas,at which point the two substances formed a hydrophilic state through water as a medium.Subsequently,the CO₂ is removed by passing N₂ or by heating to achieve recovery.The solid-to-liquid ratio,extraction time,extraction temperature and ultrasonic power were investigated as influencing factors,and the stability of the extractant was assessed by studying the structure of the PSP,the performance of the extraction,and the activity of the extractant.Subsequently,CO₂ was removed by passing N₂ or heating and the extractant could be recycled.Finally,the PSP was subjected to five cycles of the amine solvent and after the fifth cycle,the extraction rate of the PSP remained at 360.67 mg/g and the recovery of the amine solvent remained at88.4%.Through the above research,a recyclable switchable solvent was developed and applied,which has the advantages of high extraction efficiency,ease of operation,low cost and environmental friendliness;provides a green and sustainable application reference for the extraction of bioactive components from plants;and can be widely applied in the future for the extraction of nature bioactive components from plants with high application value.