Study On Extraction Of Several Natural Products By Aqueous Two-phase System

There are many different kinds of natural products in the world,which are widely used in many fields such as medicine,food,cosmetics,health products,pigment and so on.After research of several decades,the extracting technology of natural products from plants in the organic solvent-salt aqueous two-phase system has been gradually developed.Numerous studies had been fulfilled in obtaining the optimal extraction and purification of natural products.However,during different researches,the systems of extracting the same substance selected were different.Therefore,every time when extracting any natural component from plants,many attempts were required,which were not conducive to large-scale industrial production.Then,it is particularly important to find the similarity in natural products extracting by aqueous two-phase system.On the basis of extensive review of existing literature,a variety of natural products and their systems selected extracting by aqueous two-phase systems were analyzed in this thesis.Saponins,flavonoids and alkaloids were selected as research objects.In addition,platycodins,flavonoids of honeysuckle and capsaicinoids from chilies were selected as specific substances for research.Comparing the phase forming abilities of ATPS composed by four organic solvents and a variety of salts,organic solvents?ethanol,isopropyl alcohol and acetone?and inorganic salts??NH₄?₂SO₄,NaH₂PO₄ and K₂HPO₄?were chose to form aqueous two-phase systems.After extracting three kinds of natural components in the aqueous two-phase system,the optimal experimental conditions were obtained.The optimal conditions of extracting total platycodins are as follows:ethanol 25%?mass fraction?,NaH₂PO₄24%?mass fraction?,initial pH 3.92,and solid-liquid ratio 1:200,the partition coefficient?K?,recovery?Y?and yield is 13.25,94.85%and 43.75 mg/g,respectively.The optimal conditions of extracting flavonoids from honeysuckle by ATPS are as follows:ethanol 25%?mass fraction?,NaH₂PO₄ 28%?mass fraction?,initial pH3.96,and solid-liquid ratio 1:100,the partition coefficient,recovery and yield is 206.48,99.57%and 109.75 mg/g,respectively.The optimal conditions of extracting capsaicinoids are as follows:acetone 25%?mass fraction?,K₂HPO₄ 24%?mass fraction?,initial pH10.03,and solid-liquid ratio 1:100,the partition coefficient,recovery and yield is 184.80,99.47%and 8.04 mg/g,respectively.After analyzing the relationship between the structure of the extract and optimal aqueous two-phase system,it is found that the selection of organic solvent is related to the polarity of the extract,and the selection of salt is related to the ability of phase forming and the acidity of the extract.Finally,the products obtained by aqueous two-phase extraction were purified by HPLC and the compositions of products were analyzed.Separation and purification of the products of platycodins and flavonoids by liquid chromatography were both carried out by using reverse phase liquid chromatography with acetonitrile-0.2%phosphoric acid aqueous solution.The platycodin D is still not available when the product was just purified by ATPS and preparative chromatography.The rutin and luteolin can't be obtained due to the effect of chlorogenic acids.Separation and purification of the product of capsaicinoids by liquid chromatography was carried out by using methanol-water elution.Capsaicin has high purity in the product.