Salting-in counter-current chromatography separation of tanshinones based on room temperature ionic liquids

Abstract

Ionic liquids have been widely used for the extraction and separation of bioactive natural and synthetic mixtures. In this study, we provided an updated example by using an ionic liquid-based salting-in counter-current chromatography (CCC) strategy for the separation of hydrophobic tanshinones without subsequent column chromatography purification. Several ionic liquids such as 1-allyl-3-methylimidazolium chloride ([AMIM]Cl), 1-methallyl-3-methylimidazolium chloride ([MAMIM]Cl) and 1-butyl-3-ethylimidazolium chloride [BMIM]Cl could significantly decrease the partition coefficients (K) of tanshinones in the selected two-phase solvent composed of hexane-ethyl acetate-methanol-ionic liquid aqueous solution (5:5:6:4, v/v). Typically, K values of three target tanshinones including tanshinone I, 1,2-dihydrotanshinquione and tanshinone IIA were reduced from 3.57, 4.57 and 5.50 to 1.62, 2.33 and 3.08, respectively, by the inclusion of 10% [AMIM]Cl in the solvent system. After salting-in CCC separation, the purified tanshinones were obtained only by simple ethyl acetate extraction. In general, the current results demonstrated that the ionic liquid-based salting-in CCC may be as an alternative strategy for the optimization of CCC solvent systems and separation of lipophilic natural products.

Keywords: Natural product isolation; Room temperature ionic liquids; Salting-in; Salting-out; Tanshinone; Traditional Chinese medicine.