Mechanism Analysis of Selective Adsorption and Specific Recognition by Molecularly Imprinted Polymers of Ginsenoside Re.

In this article, the molecularly imprinted polymers (MIPs) of ginsenoside Re (Re) were synthesized by suspension polymerization with Re as the template molecule, methacrylic acid (MAA) as the functional monomers, and ethyl glycol dimethacrylate (EGDMA) as the crosslinker. The MIPs were characterized by Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), and surface porosity detector, and the selective adsorption and specific recognition of MIPs were analyzed using the theory of kinetics and thermodynamics. The experimental results showed that compared with non-imprinted polymers (NIPs), MIPs had a larger specific surface area and special pore structure and that different from the Langmuir model of NIPs, the static adsorption isotherm of MIPs for Re was in good agreement with the Freundlich model based on the two adsorption properties of MIPs. The curves of the adsorption dynamics and the lines of kinetic correlation indicate that there was a fast and selective adsorption equilibrium for Re because of the affinity of MIPs to the template rather than its analogue of ginsenoside Rg1 (Rg1). The study of thermodynamics indicate that the adsorption was controlled by enthalpy and that MIPs had higher enthalpy and entropy than NIPs, which contributed to the specific recognition of MIPs.

Facile optimization for chromatographic separation of liquiritin and liquiritigenin.

A reversed phase chromatographic system, composed of a stationary phase of C18 silica gel (ODS, 20µm) and a mobile phase of ethanol/water, was used to separate liquiritin and liquiritigenin in the raw material of flavonoids. The linear adsorption isotherm and the equilibrium-dispersive model were adopted to approximatively describe the chromatographic separation behaviors of liquiritin and liquiritigenin in the raw material under different column temperatures, ethanol contents and flow rates of the mobile phase, sample concentrations and feeding times. Combined with orthogonal design, the ED model was used to optimize the chromatographic separating conditions, the corresponding experimental result with a good agreement was obtained and the overload separation was realized.

Separation of Liquiritin by simulated moving bed chromatography.

Liquiritin was extracted from the natural product Licorice, and then purified using a three-zone simulated moving bed set up in our laboratory, with a C(18)-bonded silica as the stationary phase and an aqueous solution of ethanol as the mobile phase. The isotherm parameters of Liquiritin and of the only closely eluting impurity were obtained using the inverse method, fitting the experimental elution profiles to calculated elution profiles, assuming a binary Langmuir isotherm model as an approximation. The operating parameters of the simulated moving bed were selected according to the Equilibrium Theory. This allowed the preparation of 85% pure Liquiritin. Finally, 99% pure Liquiritin was obtained through a last step of recrystallization.