Ultrasound-assisted extraction of total flavonoids from Epimedium brevicornu maxim with ionic liquids: Optimization and mechanistic insight

A systematic "theory-to-experiment" paradigm integrating COSMO-RS, RSM, and molecular simulation is established for rational design of ionic liquid extraction systems. • [C₃mim]Cl is identified as the optimal solvent, achieving a total flavonoid yield of 8.15 ± 0.13 mg/g - outperforming conventional ethanol reflux by 9.7% with 77% less extraction time. • Multi-scale mechanistic studies (DFT/MD) reveal that synergistic hydrogen bonding, π-π stacking, and electronic interactions drive the enhanced extraction efficiency. • The recyclability of [C₃mim]Cl was demonstrated, and AGREE assessment confirmed its greener profile (0.66 vs. 0.27), supporting its potential as a sustainable alternative for natural product extraction. This study systematically evaluated ionic liquids (ILs) as green solvents for ultrasound-assisted extraction (UAE) of total flavonoids (TF) from Epimedium brevicornu Maxim. ( E. brevicornu ). High-performance liquid chromatography-mass spectrometry (HPLC-MS) and high-performance liquid chromatography (HPLC) analysis revealed that the extract mainly contained two flavonoids: icariin (ICA) and epimedin C (EDC). Therefore, ICA and EDC were selected as representative target compounds. The conductor-like screening model for real solvents (COSMO-RS) was used for theoretical screening. It identified 1-propyl-3-methylimidazolium chloride ([C₃mim]Cl) as the optimal solvent. Subsequent experiments confirmed this prediction, demonstrating the excellent extraction performance of [C₃mim]Cl. Next, single-factor experiments evaluated key parameters affecting flavonoid yield, and response surface methodology (RSM) was employed to optimize the extraction process. Under optimal conditions, the TF yield reached 8.15 ± 0.13 mg/g. HPLC quantification confirmed that ICA and EDC were the principal contributors. Recycling experiments verified the favorable reusability of [C₃mim]Cl, and the AGREE green analytical chemistry index further demonstrated that the established IL-UAE method possesses outstanding greenness and environmental compatibility. To understand the extraction mechanism, molecular dynamics (MD) simulations and density functional theory (DFT) calculations were performed. The results indicated that the enhanced efficiency arises from specific and energetically stable interactions between [C₃mim]Cl and the target flavonoids. This study confirms the feasibility of using ILs for efficient extraction of flavonoids from E. brevicornu , establishes a systematic methodology from theoretical prediction to experimental validation, and provides new insights for developing green extraction technologies for natural products. Download: Download high-res image (152KB) Download: Download full-size image