The Extraction And Separation Of Iridoids From Eucommia Ulmoides Male Flowers By Ionic Liquids And Deep Eutectic Solvents

Eucommia ulmoides male flowers（EUMF）are the flowers of the male plant of E.ulmoides Oliv.In China,the EUMF was approved as a new resource of food raw material in 2014.Various products including tea products,health products and functional drinks have been developed using EUMF,which have the functions of lowering blood pressure,lowering blood lipid,lowering blood sugar,anti-fatigue,and anti-aging,etc.The major active components of EUMF are chlorogenic acid,pinolidinoside,geniposidic acid and aucubin,which are similar to those of the barks and leaves of E.ulmoides.For the typical components of iridoids with similar structure and polarity,it is a great challenge to find out a new green and efficient separation method,and the research of the selective separation methods is one of the frontier research fields in separation and analytical chemistry.Ionic liquids（ILs）and deep eutectic solvents（DESs）are a new kind of designable green solvent,due to their special physical and chemical properties,are widely used in the extraction and separation of natural active ingredients,and can be used to build green liquid-liquid extraction systems to achieve efficient extraction and separation of polar compounds.Three liquid-liquid extraction systems based on ILs/DESs for the extraction and separation of GPA and AU from EUMF were designed in this dissertation.And the separation mechanism was studied.The main contents of this dissertation are as follows:（1）ILs-based aqueous two-phase systems（ATPS）were constructed using ILs and salts for the extraction and separation of GPA and AU.The binodal curves were fitted to the nonlinear Merchuk relationship.The abilities of these ILs to form ATPS increase with the increase of their alkyl side chains.The distribution behavior of GPA and AU in this ATPS was discussed by investigating the extraction factors of the types and amounts of ILs and salts,extraction temperature,extraction time,and sample addition amount.It was found that the maximum extraction efficiency(E_1AU=96.95%,E_1GPA=99.99%),distribution coefficients(log K_AU=1.54 and log K_GPA=4.47),and selectivity（S=843.57）were obtained in the ATPS constructed by 25%（w/w）[Bmim]Br and 30%（w/w）K₂CO₃.Furthermore,[Bmim]Br was converted into hydrophobic[Bmim]NTf₂ by a double decomposition reaction of Lithium bis（trifluoromethanesulfonimide）to recover ILs.Density functional theory（DFT）calculation further showed that the H-bond interactions were the main factor affecting the extraction of GPA and AU in this method.（2）A hydrophilic/hydrophobic DESs two-phase system was constructed for the extraction and separation of GPA and AU.On the basis of the idea that the density and polarity of hydrophilic and hydrophobic DESs can be used for separating similar structures.nine kinds of hydrophobic DESs used menthol,thymol,quaternary phosphonium salt,quaternary ammonium salt and trioctyl phosphonyl oxide as HBAs,as well as six hydrophilic choline chloride DESs were prepared and used to construct the two-phase system for the selective separation of GPA and AU.The optimum conditions are as follows:the volume ratio of N₄₄₄₄Cl-HA and Ch Cl-LA is 3:1,the initial GPA and AU concentration is 2.0 mg/m L,the temperature is 25℃,the p H value of buffer salt is 2.53.The distribution coefficient of GPA and AU are 17.50 and 0.24,respectively,and the selectivity coefficient can reach 71.99.DFT calculation shows that H-bond interaction is the main factor affecting the selective separation of GPA and AU.（3）The solid-liquid extraction and separation of GPA from EUMF via temperature responsive ILs/water system was studied.Generally,the quaternary phosphonium salt ILs had Lower critical solution temperature（LCST）behavior.In this study,based on quaternary phosphonium salt(P₄₄₄₄OH)and benzimidazole（BZIM）,a temperature responsive ILs(P₄₄₄₄BZIM)with LCST response behavior was synthesized by acid-base neutralization reaction.The functional group changes of P₄₄₄₄BZIM at different temperatures were characterized by variational temperature ¹H NMR,variational temperature IR and dynamic light scattering.The critical temperatures of P₄₄₄₄BZIM/water system with different ratios were determined by turbidimetric method.The effects of P₄₄₄₄BZIM concentration,solid-liquid ratio,extraction temperature,extraction time and ultrasonic power on the yield of GPA from EUMF were investigated.And the maximum yield of GPA was obtained at 0.22 mg/g under the optimal conditions.Moreover,GPA and ILs were recovered by reversible homogeneous and biphase transformation of P₄₄₄₄BZIM/water system,and P₄₄₄₄BZIM could be recycled for 5 times.