A LCST-type ionic liquid used as the recyclable extractant for the extraction and separation of liquiritin and glycyrrhizic acid from licorice (Glycyrrhiza uralensis Fisch)

Abstract Recently, the use of stimuli-responsive ionic liquids (ILs) as extractants has received close attention due to their retrievability. In this study, a temperature-responsive ionic liquid (TR-IL) was synthesized and used for the extraction and subsequent separation of liquiritin (LQ) and glycyrrhizic acid (GA) from licorice (Glycyrrhiza uralensis Fisch) root. This TR-IL was used as the extractant below its lower critical solution temperature (LCST), whereas it became hydrophobic to form a biphasic system to separate the two target compounds above its LCST. LQ and GA were distributed in the IL and aqueous phases, respectively. Moreover, the factors influencing the extraction and separation processes were studied to optimize the experimental conditions. The extraction yields of 9.63 and 28.51 mg/g and the distribution coefficients of 3.2 and 4.42 were obtained for LQ and GA, respectively. The selectivity coefficient of this biphasic system for LQ and GA was 14.2. Finally, the TR-IL was recycled and reused after extraction and separation. This study developed an efficient, green and sustainable strategy for the extraction and selective separation of bioactive ingredients from natural products.