Novel process for selective separation of trace artemisitene from artemisinin by ammonium functional ionic liquids

One of the challenges to obtain high-quality natural active substances is the selective separation of the target compound from its analogues. In this study, ionic liquids (ILs), with design flexibility, were proposed to separate artemisitene and artemisinin, typical examples of natural analogues. Based on COSMO-RS calculation, several ILs were selected to separate artemisitene/artemisinin by experiment. It was demonstrated that the aqueous solution of N-allyl-N,N,N-trimethylammonium chloride ([AA][Cl]) exhibited excellent capability for selective separation of the two compounds. Under the optimal conditions (40 degrees C, 1 h), the separation selectivity of artemisitene/artemisinin could reach 12.23 when the initial impurity content was only 0.8 wt%. Spectroscopic analysis and molecular dynamics indicated that pi-pi complexation between artemisitene and [AA][Cl] plays a major role in this separation process. Moreover, the process of multistage cross-flow extraction was compared with counter-flow extraction, and the latter one exhibited advantages in energy consumption and product yield.