Separation And Purification Of The Active Ingredients In Aloe Vera L. Using Aqueous Two-phase System

In this paper, we have studied four aqueous two-phase systems (ATPSs) of PEG/salt, cloud point extraction (CPE), alcohol/salt and ionic liquid (IL)/salt. Meanwhile, the four systems were used in extraction, separation and purification of aloe anthraquinones, polysaccharides.Firstly, we have optimized the extraction process of aloe anthraquinones and polysaccharides by the central composite design and response surface methodology (CCD-RSM). The influencing factors to anthraquinones yield of concentration of ethanol, extraction time and liquid solid ratio were investigated. The influencing factors to polysaccharides yield of extraction temperature, extraction time and liquid solid ratio were investigated. The experiments were designed by3factors and5levels, the3D response surface plots were drawn. The optimal conditions were obtained by analysis and pridiction of the experimental results.Secondly, the PEG/salt ATPS was used in separation and purification of aloe anthraquinones. The factors of pH, inorganic addictive and temperature were investigated by the optimal PEG/salt system. The anthraquinones were extracted into PEG-rich phase after ATPS extraction and then the back extraction was achieved by adjusting pH.Thirdly, the CPE based on a non-ionic surfactant Triton X-114was used to separate and purify aloe anthraquinones. The influencing parameters of Triton X-114concentration, pH, equilibrium temperature and time and the addictive of NaCl were investigated. Aloe anthraquinones were extracted into aqueous phase by back extraction, and the surfactant can be recycled. The analytical characteristics and the validity of this method were analyzed.Fourthly, the alcohol/salt ATPS was used in extraction and purification of aloe anthraquinones. The factors of the type and concentration of alcohol and salt, temperature and pH were investigated. Under the optimal condition, majority of anthraquinones were extracted into alcohol-rich phase and the impurities of polysaccharides, proteins and mineral substance were extracted into salt-rich phase. The alcohol in alcohol-rich phase can be recycled by evaporation and the salt in salt-rich phase can be recycle by dilution crystallization. The major constitutes of aloe anthraquinones were aloe-emodin by HPLC analysis. The distribution of anthraquinones in alcohol/salt ATPS were influenced by hydrophobicity, salting-out effect and hydrogen bond interaction through investigating the extraction mechanism. The thermodynamics also demonstrated that temperature can affect the distribution to a great extent.Fifthly, a series of iminazole IL intermediate with different length of carbon chain were synthetized. Then ILs with different anion were synthetized by ion-change method. Furthermore, the functionalized ILs were synthetized. The ILs were charactered by IR and HMNR. The ATPSs were constructed using IL and salt, the phase equilibrium was studied and the phase diagram and tie line were drawn.Sixthly, the IL/salt ATPS was used in simultaneous extraction and purification of aloe polysaccharides and proteins. Polysaccharides were extracted into salt-rich phase, while majority impurities of proteins, mineral substance and phenol compounds were extracted into IL-rich phase. The optimal condition was obtained by studying the distribution of polysaccharides and proteins in ATPS, the factors of salt type and concentration, temperature, pH, inorganic addictive were investigated. Polysaccharides after ATPS extraction were further purified by dialysis membrane, IL and salt were filtrated leaving polysaccharides in the dialysis tube. The TG analysis demonstrated this method can obtain polysaccharides with higher purity.[C4mim]BF4in IL-rich phase was extracted into CH2CI2,[C4mim]BF4can be recycled by evaporating CH2Cl2.Lastly, the IL/salt ATPS was used in separation and purification of anthraquinones.[C4mim]BF4was chosen as the phase-forming IL due to its good phase-forming ability and extraction ability. The influencing system parameters of type of IL, type and concentration of salt, extraction temperature and pH were investigated. Under the optimal condition, anthraquinones can be extracted into IL-rich phase by a single-step extraction and majority impurities were extracted into salt-rich phase. The major components of aloe-emodin and chrysophanol were analyzed by HPLC before and after ILATPS. Compared with conventional liquid-liquid extraction, this ILATPS is more efficient and environment friendly.The advantages and disadvantages of the four types of ATPSs were compared in this paper, which pvovide a theoretical direction in the separation field.