Deep eutectic solvents (DESs) are green organic solvents that have broad prospects in the extraction of effective components of traditional Chinese medicine. This work employed the quantitative analysis of multi-components by a single marker (QAMS) method to quantitatively determine the six effective components of glycyrrhizic acid, liquiritin, isoliquiritin apioside, liquiritigenin, isoliquiritin, and glycyrrhetinic acid in Glycyrrhiza uralensis, which was used for comprehensive evaluation of the optimal extraction process by DESs. First, Choline Chloride: Lactic Acid (ChCl-LA, molar ratio 1:1) was selected as the most suitable DES by comparing the extraction yields of different DESs. Second, the extraction protocol was investigated by extraction time, extraction temperature, liquid-to-material ratio, molar ratio, and ultrasonic power. The Box-Behnken design (BBD) combined with response surface methodology (RSM) was used to investigate the optimal DES conditions. The result showed that the best DES system was 1.3-butanediol/choline chloride (ChCl) with the molar ratio of 4:1. The optimal extraction process of licorice was 20 mL/g, the water content was 30%, and the extraction time was 41 min. The comprehensive impact factor (z) was 0.92. At the same time, it was found that the microstructure of the residue extracted by the eutectic solvent was more severely damaged than the residue after the traditional solvent extraction through observation under an electron microscope. The DES has the characteristics of high efficiency and rapidity as an extraction solution.
Keywords: DES; QAMS; flavonoids; saponins; ultrasonic-assisted extraction.