Deep Eutectic Solvent-Based Microwave-Assisted Extraction for the Chromatographic Analysis of Bioactive Flavonoids in Spirodela polyrrhiza

Deep eutectic solvents (DESs) are regarded as promising solvents to extract chemicals from plant materials. In this study, a DES-based microwave-assisted extraction (MAE) method was developed for the chromatographic analysis of four bioactive flavonoids in Spirodela polyrrhiza. Chromatographic separation was achieved on a Promosil C-18-column. Prior to the HPLC analysis, the flavonoids were rapidly extracted by a DES-MAE process using choline chloride/levulinic acid (1:2, mol/mol) as the solvent. The extraction parameters were optimized using response surface methodology, and the optimal DES-MAE was fast and efficient compared with conventional solvent-based MAE and ultrasonic-assisted extraction using DES. The recoveries of optimized DES-MAE for the four flavonoids ranged from 97.80 to 103.29%. This study demonstrates that the validated DES-MAE-HPLC method is efficient, accurate and applicable to the determination of flavonoids in S. polyrrhiza.