Deep-eutectic solvents/ionic liquids/water mixture as a novel type of green thermo-switchable solvent system for selective extraction and separation of natural products from Rosmarinus officinalis leaves

In the present study, we designed a novel type of green thermo-switchable solvent system which is composed of ChCl:LA/[BMIM]PF6/H2O (v/v/v, 1/2/1) to extract natural products. When the temperature is 60 ℃, the system is a homogeneous single-phase system, and when cooling to 25 ℃, the system is switched into a heterogeneous two-phase system. Based on the thermo-switchable system, an integrated extraction method was developed which could efficiently extract both rosmarinic acid (hydrophilic) and carnosic acid (hydrophobic) from Rosmarinus officinalis leaves at 60 ℃ and in situ separate the extracted compounds with high recovery yields by cooling the extracts to 25 ℃. Rosmarinic acid was separated into the upper phase (88.97%) and carnosic acid was separated into the lower phase (97.46%). In addition to enhanced efficiency and no consumption of organic solvents, the method also completed the extraction and separation in a single step which further reduced the operation units.