Selective Separation Of Active Components From Rhodiola Rosea And Tea By Fractional Extraction

With ever-increasing concerns on medical health,the active ingredients in plants are widely used in medicine,food,and daily necessities.However,there are many kinds of plants with complex composition and different contents of active ingredients,and some of them varieties even contain toxic ingredients.Therefore,it is of great significance to selectively separate active ingredients from plants.In this thesis,the centrifugal extraction technique was used to selectively separate active substances from Rhodiola rosea extract and Tea extract.The separation and purification of tyrosin,picoside,salidroside from Rhodiola rosea and epigallocatechin(EGC),epicatechin(EC),caffeine(CAF)from tea were studied.Extraction systems were constructed by liquid-liquid extraction experiments.According to the law of phase equilibrium and mass balance,the corresponding mathematical model was established,which was used to simulate and optimize the separation process.Fractionation extraction experiments were carried out by using centrifugal extractors to separate and purify the target active ingredients.The main research and results were as follows:1.Separation and purification of tyrosol,picroside and salidroside from Rhodiola rosea extract.N-amyl alcohol,isobutyl acetate and n-butanol were used as organic phases to establish three extraction systems for the separation and purification of tyrosol.When n-amyl alcohol was used as the organic solvent,the distribution coefficients of tyrosol and picrin were 14.30 and2.764,respectively,and the separation factor between them was 5.174.Subsequently,the purity of tyrosol with 98.8% and the yield with 93.1% were obtained in a cascade of 10 stages.When isobutyl acetate was used as the organic solvent,the partition coefficients of tyrosol and picrin were 2.615 and 0.533,and the separation factor between them was 4.906.The purity of tyrosol with 94.6% and the yield with 84.9% were obtained in a cascade of 10 stages When n-butanol was used as the organic solvent,the distribution coefficients of tyrosol,picrin and salidroside were infinite,3.236 and 0.748,respectively,and the separation factor of picein and salidroside was 4.325.Under the condition of 10-stage centrifugal extractor,the purity of tyrosol was 95.4%and the yield was close to 100%.All the three extraction systems showed good separation effects of separating tyrosol,indicating that there was a wide selection of organic solvents under appropriate conditions.When n-butanol was used as organic solvent,the yield of tyrosol was the highest.Therefore,the aqueous phase obtained from this extraction system was used as the raw material for the subsequent separation process.The aqueous phase without tyrosol was used and extraction as the feed phase,and n-butanol was used as the organic solvent to separate picroside.Under the condition of 10-stage centrifugal extractor,the purity and yield of picoside were 93.6%and 63.6%.After the separation of tyrosol and picoside,the aqueous phase without tyrosol and picoside was used as the feed phase to carry out the third step centrifugal extraction for the separation of salidroside.the purity of salidroside with 97.3% and the yield with 73.4% were obtained in a cascade of 10 stages.2.Separation and purification of EGC,EC and CAF from Tea extract.Firstly,EGC and EC were regarded as the target group,and them were separated from other components by two-step fractionation extraction.Then a third step fractional extraction was performed to separate EGC and EC.In the first step,butyl acetate was used as the organic phase.The target group and substances with distribution coefficients smaller than the target group were separated into the aqueous phase in a cascade of 10 stages.At this time,the yield of EGC and EC obtained was89.8% and 89.2%,respectively.In the second,butyl acetate was still used as the organic solvent to separate the target group and other monomers with distribution coefficient smaller than those of the target group.Under the condition of 20-stage centrifugal extractor,the target group was obtained in the organic phase,and the yield of EGC and EC were 73.1% and 97.1%,respectively.For the third,a mixed solvent of butyl acetate and n-hexane(8:1,v/v)was used as the organic solvent.In a cascade of 10 stages,the purity and yield of EGC in aqueous phase were 83.7% and95.8%,the purity and yield of EC in organic phase were 99.1% and 50.7%,respectively.During the separation and purification of CAF,a two-step fractionation extraction was adopted in a cascade of 10 stages.In the first step,a mixed solvent of n-butanol and ethyl acetate(1:1,v/v)was used as the organic solvent,and the substances with a distribution coefficient greater than CAF were separated from CAF;in the second step,n-butanol was used as organic phase and then CAF with purity of 98.4% and yield of 55.2% was obtained.