Selective Isolation Of Components From Natural Volatile Oil By Countercurrent Chromatography Based On Coordination Complex And Its Theory

This work concentrates on the application of two selective reagents including ?-cyclodextrin derivatives,including ?-cyclodextrin(?-CD),methyl-?-cyclodextrin(Me-?-CD)and hydroxypropyl-?-cyclodextrin(HP-?-CD),as well as metal ion selective reagent silver nitrate in selective isolation of components from seven kinds of volatile oil by high speed countercurrent chromatography(HSCCC).The chromatographic retention mechanism of the volatile oil of Curcumae Rhizoma by high performance liquid chromatography(HPLC)with Me-?-CD as selective reagent was proposed and discussed.The seven kinds of volatile oil were as follows: Curcumae Rhizoma,Chuanxiong Rhizoma,Myristicae Semen,Aucklandiae Radix,Angelicae Sinensis Radix,Artemisiae Annuae Herba,Foeniculi Fructus.First,liquid-liquid partition experiment was used to estimate thepartition performance of chemical components of volatile oil in the biphasic solvent system.The biphasic solvent system composed of n-hexane-0.10 mol/L cyclodextrin(1:1,v/v).All kinds of volatile oils are from seven kinds of traditional Chinese herb.The eluent of the HSCCC was detected by the GC-MS and the component from eluted fractions was recovered and identified by 1H NMR.Results showed that eight chemical components could be well separated with high purity from each kind of volatile oil using different type of cyclodextrin as selective reagent.For example,germacrone and curcumenone could be selectively separated from volatile oil of Curcumae Rhizoma with Me-?-CD and HP-?-CD as selector respectively,senkyunolide A could be selectively separated from volatile oil of Chuanxiong Rhizoma with Me-?-CD and HP-?-CD as selector,?-terpineol and methyleugenol could be selectively separated from volatile oil of Myristicae Semen with ?-CD and HP-?-CD as selector respectively,trans-?-ionone could be selectively separated from volatile oil of Aucklandiae Radix with HP-?-CD as selector,ligustilide could be selectively separated from volatile oil of Angelicae Sinensis Radix with Me-?-CD as selector.Then,silica gel column chromatography has been used to enrich the?-elemene and its content could be increased from 16.5% to 46.1%.Liquid-liquid partition experiment was used to measure the partition coefficent(K)of ?-elemene.According to the K values,a solvent systemcomposed of n-hexane-methanol-water(2:1.5:0.5,v/v/v)containing0.15 mol L-1 of silver ion was selected for the separation experiment.Tail-to-head elution mode was used for HSCCC separation.And the purity of the ?-elemene from this separation could reach 99%.Finally,the elution behavior of sesquiterpenoids in volatile oil of Curcumae Rhizoma on reverse stationary phase high performance liquid chromatography with Me-?-CD as mobile phase additive was studied.The main analytes of sesquiterpenoids are germacrone,curzerene and furanodiene.Stoichiometric coefficient and apparent formation constants of the inclusion complex between Me-?-CD and the analyte were calculated by varying the concentration of the additive in the mobile phase composed of methanol and water(90:10,v/v),in which the association constant for inclusion complex between the organic modifier methanol and Me-?-CD was also determined.Results showed that stoichiometric coefficient of all studied inclusion complex was 1:1 within the concentration 0-9 mmol L-1 of Me-?-CD in the mobile phase and an unusual retention behavior of the analyte germacrone was found,which was further testified by the thermodynamic parameters.The enthalpy and entropy of the inclusion complexes and of solute-stationary phase interactions were calculated from linear van't Hoff plots.In sum,selective isolation of chemical constituents from volatile oil by countercurrent chromatography with substituted ?-cyclodextrin and silvernitrate as selective reagent was investigated.The current studies demonstrated that this method would give much higher separation factor,shorter separation time and higher purity for the target component.This work provided an alternative way for preparative separation of chemical components from natural volatile oil.