Room temperature ionic liquids-based salting-in strategy for counter-current chromatography in the separation of arctiin

Abstract Counter-current chromatography (CCC) is a solid support-free liquid-liquid partition chromatography and has wide applications. However, CCC separation is still a challenging process and the selection of appropriate solvent system for separation of target compound(s) is still relatively time-consuming. In this work, we introduced a room temperature ionic liquids-based salting-in strategy for the rapid selection of suitable solvent systems for CCC separation. In the randomly selected solvent systems, such as ethyl acetate-water, n- butanol-water, n- pentanol-water, n- hexanol-water, and n- octanol-water, several ionic liquids such as [AMIM]Cl, [MAMIM]Cl, and [BMIM]Cl can increase the solubility of the solutes in the lower phase, which made a dose-dependent decreasing of partition coefficient of solute in the two-phase solvent system. Thus, it is possible to get a suitable solvent system with sweet K spot such as K  = 1 only by adding some ionic liquids into the systems. As an example, arctiin, a bioactive lignin component of the fruit of Arctium lappa. L. (Niubangzi in Chinese), was selected and successfully separated by CCC with room temperature ionic liquids-based n- butanol-water systems. It seems a very efficient alternative strategy for the optimization of solvent systems for CCC separation of natural products.