Study On The Selective Separation Of EGCG And ECG In Tea Polyphenols By Fractionation And Extraction

Tea polyphenols is the general name of polyphenols in tea,among which EGCG is the most active component with the highest content.EGCG has powerful ability to remove oxygen free radicals,which can prevent and treat cancer,heart disease and many other diseases.ECG has significant effect on preventing atherosclerosis and inhibiting human viral infection.At present,there is no effective method for large-scale isolation of EGCG and ECG monomers from tea polyphenols.Therefore,the selective separation of high value-added functional active components EGCG and ECG in tea polyphenols has important scientific significance and practical application value.In this paper,the continuous and selective separation of EGCG and ECG in tea polyphenols was realized by multi-stage centrifugal fractional extraction technology for the first time.The main research work and results are as follows:1. The mathematical model of liquid-liquid extraction was based on phase equilibrium and mass conservation.In this work,solvent extraction without reactive extractant was used,and only physical distribution exists.The components of tea polyphenols were complex.We introduced the residual rate to simulate and optimize the separation process.2. EGCG was selectively separated from tea polyphenols by multistage centrifugal fractional extraction.Firstly,butyl acetate-water was used as extraction system I to separate the monomers with smaller distribution coefficient than EGCG in tea polyphenols.The mixture of isobutyl acetate and n-hexane?20:80,V/V?was used as extraction system II to separate EGCG from monomers with larger distribution coefficient.Combining the two extraction systems,two new methods of batch separation and continuous separation based on two-step extraction were explored to separete EGCG.A multistage liquid-liquid extraction model was established,and the residual rate was proposed to describe the purity and impurity content of the product.The influence of process parameters such as the phase ratio and the number of stages on the extraction efficiency were studied,and the best process conditions of EGCG separation were obtained.EGCG with a purity of higher than 99%was separated from tea polyphenols by continuous separation method,and the yield is as high as 98%.Through batch separation,the purity of EGCG is up to 99%in the water phase with a yield about 100%,which is in line with the model prediction3. ECG was selectively extracted from tea polyphenols by multistage centrifugal fractional extraction.A highly efficient extraction system without reactive extractant was established.The mixed solvent of n-hexane and butyl acetate?20:80,V/V?was used as the extraction phase with k _ECGof 9.98,the k _GCGof 4.56,and?of 2.18.In order to study the influence of phase ratio,feed position and the number stages,a centrifugal fractional extraction model was established to optimized the separation process.The residual rate is introduced to express the content of other low concentration substances when ECG is separated from multi-component mixture.Optimal parameters for the separation of ECG from tea polyphenols were obtained by simulation and optimization.Under the condition of F/W ratio of 0.2 and O/W ratio of0.15,the purity of ECG was nearly 100%and the yield was 94%by 20 stage centrifugal fractional extraction and feeding in the middle stage.