Menthol-Based Hydrophobic Deep Eutectic Solvent for Vortex-Assisted Liquid-Liquid Microextraction and Capillary Electrophoretic Determination of Bioactive Compounds in Licorice

Abstract

A novel hydrophobic deep eutectic solvent (HDES) composed of menthol and lactic acid was successfully synthesized and applied for the simultaneous vortex-assisted liquid–liquid microextraction (VA-LLME) of triterpenoids (glycyrrhizic acid, GL, and glycyrrhetinic acid, GA) and a flavonoid (chalcone A, ChA) from licorice extract. Under the optimized conditions using 5 mL of plant extract and 800 μL of HDES, the target analytes were efficiently extracted via vortex mixing and centrifugation, with the resulting HDES phase directly analyzed by high-performance capillary electrophoresis (HPCE). The proposed method demonstrated excellent linearity (3–600 μg/mL, R² > 0.9954) for all analytes. The limits of detection (LODs) and quantification (LOQs) ranged from 0.67 to 2.97 μg/mL and 2.22 to 9.90 μg/mL, respectively. Intra-day and inter-day precision (RSD) were below 4.21% and 6.41%, with recoveries between 91.51% and 105.1%. The method is relatively sensitive, showing particularly good enrichment for GL and GA in licorice, and can be applied to the purification of triterpenoids from this herb. Overall, this approach is simple, rapid, environmentally friendly, and has been successfully applied to the accurate quantification of triterpenoids and flavonoids in licorice extract.