Ultrasound-assisted extraction of polyphenols from Moutan Cortex using natural deep eutectic solvent: Optimization, molecular mechanisms, and lipid-lowering activity.

Moutan Cortex is a valuable medicinal resource rich in bioactive polyphenols, yet its sustainable valorization is often hindered by the inefficiencies and environmental concerns associated with conventional extraction methods. In this study, a green and efficient ultrasound-assisted extraction (UAE) strategy was developed using a betaine-levulinic acid (Bet-LevA) natural deep eutectic solvent (NADES). An intelligent optimization approach was applied to determine the optimal extraction conditions, achieving a maximum total polyphenol content of 27.03 ± 0.41 mg GAE/g DW, which was 1.93-fold higher than that obtained using 70% ethanol extraction. The molecular mechanisms underlying the superior extraction performance of Bet-LevA were further elucidated using FT-IR, conductor-like screening model for realistic solvents (COSMO-RS), and molecular dynamics (MD) simulations, revealing that hydrogen-bond networks and stronger solvent-polyphenol interactions promoted solubilization and stabilization of phenolic compounds. Furthermore, the extracted polyphenol fraction effectively alleviated fatty acid-induced lipid accumulation in AML-12 hepatocytes. Overall, this study provides a sustainable extraction framework integrating green solvent design, intelligent optimization, molecular mechanism analysis, and functional evaluation for the high-value utilization of Moutan Cortex in functional foods and nutraceutical applications.