Microwave-assisted Extraction Of Lactone From Ligusticum Chuanxiong Hort. Using Ionic Liquid

For the past thousands years, traditional Chinese medicine is the main source for medical treatment in China. As an important approach, extraction method is usually adopted in separating bioactive ingredients from Chinese medicine. However, volatile traditional organic solvents are commonly used in the extraction process, which would lead to environment pollution and solvents loss. At the same time, it is very time consuming and the extraction efficiency is low. In this work, in order to improve the extraction process and develop a greener process, a microwave-assisted extraction (MAE) method was investigated to extract Senkyunolide I, Senkyunolide H and Z-ligustilide from Ligusticum Chuanxiong Hort.. Three ionic liquids, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Bmim][NTf2]), N,N-Dimethyl-N-(2-hydroxyethoxyethyl) ammonium propionate (DMHEEAP) and N,N-Dimethyl(cyanoethyl) ammonium propionate (DMCEAP), were employed as extractants in the extraction process.Four important factors such as system temperature, extraction time, solid-to-solvent ratio and particle size were studied for the three ionic liquids. Reverse HPLC method was employed for quantitative analysis. The yield of the three target ingredients was compared between [Bmim][NTf2] MAE and solvent reflux extraction (SRE), and matrix surface structure was studied by scanning electron microscope (SEM). Reuse and back-extraction of used ionic liquids were also studied.The results show that system temperature is the key factor of extraction process. And extraction efficiency increases as system temperature raise, sharp increasing for [Bmim][NTf2] and smooth increasing for DMHEEAP and DMCEAP. Extraction equilibrium can be achieved in a very short time, one minute for [Bmim][NTf2] and DMHEEAP, five minutes for DMCEAP. Extraction efficiency is not improved by increasing time, while longer extraction time leads to the decrease of extraction efficiency for Z-ligustilide in DMHEEAP and DMCEAP. For the limited solid-to-solvent ratio and particle size range experiments, solid-to-solvent ratio and particle size do not influence the extraction efficiency. Compared to SRE, [Bmim][NTf2]-MAE requires less time and gives higher extraction efficiency, an increase of 46% is reached for Z-ligustilide with [Bmim][NTf2]-MAE. Surface structure damage is noticed in MAE treated matrix through SEM study, which will be beneficial to the improvement of the extraction efficiency. No efficiency drop is noticed after the reuse of [Bmim][NTf2] for three times. But efficiency drop is noticed for DMCEAP and DMHEEAP in the reuse study, especially for DMHEEAP. This result can be attributed to property change, such as viscosity, in ionic liquids after several times of extraction, some ingredients from Ligusicum Chuanxiong Hort. are accumulated in ionic liquids. After back-extraction with water and n-hexane, concentration of Senkyunolide I, Senkyunolide H and Z-ligustilide in [Bmim][NTf2] are dropped to 15.8%,21.3% and 23.4% compared to the mount before back-extraction, respectively. Additionally, after back-extraction with n-hexane, concentration of Senkyunolide I, Senkyunolide H does not change in DMCEAP and DMHEEAP. For Z-ligustilide, the concentration drops to 39.7% and 54.7% for DMCEAP and DMHEEAP, respectively. The result shows that ingredients of different polarity can be enriched in ionic liquids by choosing different back-extraction solvents.From the above results, ionic liquid MAE method takes short time, gives high extraction efficiency and less solvent and energy consumption. It is a high-efficiency, safe and green method, which will be potentially applied in natural product extraction with large scale in the future.