| Glabridin is the main hydrophobic ingredient in flavonoids. The glabridin content is about11%in licorice flavonoids and about0.2%in Glycyrrhiza glabra L.. Hence, the separation and purification technologies of glabridin are the key processes in the development of Glycyrrhiza glabra L.. In this pater, the extraction of glabridin from Glycyrrhiza glabra L, the extraction and mechanism of glabridin using ionic liquids were studied. The research of glabridin are as follows:A reverse phase high performance liquid chromatographic method is used for determination of glabridin in Glycyrrhiza glabra L.. The yield of glabridin is regarded as evaluation index. The effects of extraction solvent, extraction method and extraction technology are studied. The results show that the microwave-assisted extraction method is appropriate for extraction of glabridin. The optimal extraction technology is extraction solvent of ethanol/water (70:30, V/V), the solid/liquid ratio of1:15(g/mL), extraction temperature of65℃, extraction time of40minutes and times of one. The yield of glabridin reached to2.56%o.To extract glabridin from licorice extract using imidazolium-based ionic liquids (ILs), a series of1-alkyl-3-methylimidazolium ionic liquids with different anions and alkyl chain lengths of cations are selected. The different ionic liquids, extraction technology and back extraction of ionic liquid are investigated. It is concluded that the optimal IL is1-Hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C6mim][NTf2]). The extraction efficiency of glabridin using [C6mim][NTf2] is96.04%under the optimal conditions of0.40mg-mL-1glabridin concentration, pH=7, phase volume ratio (VIL/VLE) of1:3, and extraction time of40min. The back extraction of glabridin from [C6mim][NTf2] is used by2.0mol·L-1sodium hydroxide solution. The recovery rate of glabridin is98.96%in the first cycle, ionic liquids may recycle5times at least.Density functional theory (DFT) calculations using the B3LYP (Becke’s three-parameter exchange functional in combination with the Lee, Yang, and Parr correction functional) have been carried out with the Gaussian09program. Geometry optimizations have been performed at the B3LYP/6-31+G(d) level without symmetry constraints for the glabridin (GD), acetate anion ([OAc]-), tetrafluoroborate anion ([BF4]-), hexafluorophosphate anion ([PF6]"), GD-[OAc]-complex, GD-[BF4]-complex, and GD-[PF6]-complex. The interactions of glabridin (GD) with ionic liquid (IL) anions have been investigated using DFT. Geometric parameters, interaction energies, vibration frequencies, natural bond orbital (NBO) are studied on GD and GD-anion complexes. The results indicate that the hydrogen bonding interactions exist in GD and IL anions. The strengths of interactions of GD-anion complexes follows the order: GD-[OAc]-complex> GD-[BF4]-complex> GD-[PF6]-complex. The computational results are in accord with the experimental analysis.Glycyrrhiza glabra L is rich in Xinjiang, this study provide a theoretical basis for the development of natural products active ingredients in efficient, energy saving, environment-friendly solvents and extraction methods. The present study may be used as a reference in the purification of glabridin using ILs. |
