Characteristics Of Acidic Deep Eutectic Solvent And Its Application In The Preparation Of Quercetin By Hydrolyzing Rutin

Flavonoids are widely found in plants and have strong biological activity and high nutritional value.Because of its large molecular weight and poor membrane permeability,it is difficult to be directly absorbed and utilized by the human body.The preparation of flavonoid aglycones has become one of the effective solutions.The experimental group has found that acidic deep eutectic solvent(DES)can not only improve the solubility of flavonoids,but also hydrolyze glycosidic bonds to prepare flavonoid aglycones under the condition of water and heating.At present,the hydrolysis mechanism of flavonoids in acidic DES remains unclear.And its application in the food field needs to be developed.Therefore,this paper studies the hydrolysis mechanism and application of flavonoids represented by rutin as a model.In this paper,the hydrolysis kinetics and catalytic mechanism of rutin in acidic DES were studied by the relationship between the acidity of acidic DES and the hydrolysis ability of rutin.Edible deep eutectic solvents(EBDES)with food additives were developed.And the physicochemical properties were measured and characterized.Finally,EBDES(glycerol-citric-water)was applied to the extraction of quercetin from Sophora japonica.The extraction process of quercetin from Sophora japonica was optimized by single factor experiment and response surface analysis.The results of this paper provide a reference for the application of EBDESs in the preparation of flavonoid aglycones in food industry.The main work and conclusions of this paper are as follows:Firstly,the transformation behavior of Rutin in 10 DESs was studied,including Ch Cl-Malonic acid,Ch Cl-Malic acid,Ch Cl-Citric acid,Ch Cl-Glycerol,Ch Cl-Sorbitol,Ch Cl-Propan-1,3-diol,Ch Cl-Maltose,Ch Cl-Sucrose,Ch Cl-Fructose,and Ch Cl-Glucose.Rutin was degraded into quercetin only in Chcl-malonic acid,Chcl-L-malic acid and Chcl-citric acid.The ionic solution with the same composition as acidic DES was prepared,and the degradation and transformation process of rutin was studied.It was found that rutin could be degraded and transformed into quercetin only in acidic solution,and the hydrolysis ability increased with the enhancement of acidity.The effects of heating temperature and heating time on the degradation of rutin was studied.The higher the temperature,the faster the degradation rate.The degradation kinetic data of rutin in 10%and 40%water content choline chloride citric acid(Chcl citric)system were investigated.The reaction rate accorded with the first-order reaction kinetic model.Secondly,10 EBDESs were developed,including Glucose Malic,Fructose Malic,Glycine Malic,Glycerol Malic,Sorbitol Malic,Glucose Citric,Fructose Citric,Glycine Citric,Glycerol Citric,and Sorbitol Citric.The differences of density and viscosity were studied.It was found that the density and viscosity of citric acid system were greater than malic acid system.The hydrolysis ability,Hammett acidity,solubility and solvation color parameters of EBDESs were studied.It was found that the hydrolysis capacity of rutin in citric acid system was greater than malic acid system.The solubility of rutin in malic acid system is greater than that of citric acid,both higher than 1.5 mg/m L.The polarizability and ability to form hydrogen bonds of EBDESs are discussed through E_T,π*,β,andα.It was found that among the 10 EBDESs,the ability of the malic acid system to form hydrogen bonds was greater than that of the citric acid system.Finally,the glycerol-citric acid system was applied to extract quercetin from Sophora japonica.The effects of water content and temperature on the rate of hydrolysis were studied.It was found that the system with 40%water hydrolyzed rutin faster.And it was suitable for the extraction of quercetin with the temperature between 70 and 100℃.It was applied to extract quercetin from Sophora japonica.The ultrasonic power of 540 W,the extraction and transformation temperature of 80℃,and the extraction and transformation time of 90 min were selected by single factor experiment.Box-Behnken method was used to design the response surface,and the Design-expet 8.05 software was used to optimize the model.According to the actual operability,the ultrasonic power was 570 W,the extraction and conversion temperature was 87℃,and the extraction and conversion time was 120 min.The antioxidant capacity of the extract was discussed by DPPH radical scavenging rate and FEAP.It showed that the extraction has good antioxidant capacity.