Construction of Green System for Flavonoids from Dalbergia Pinnata (Lour.) Prain Based on NADES-UAE: Intelligent Optimization–Molecular Mechanism–Activity Verification

To promote green chemistry and improve the utilization of plant resources, flavonoids from Dalbergia pinnata (Lour.) Prain were extracted in this study by combining NADES (natural deep eutectic solvents) with UAE (ultrasound-assisted extraction). Among the 13 synthesized NADES, choline chloride (ChCl)–urea (NADES-13) exhibited the highest extraction rate, outperforming traditional organic solvents. The optimal conditions determined by response surface methodology (RSM) were as follows: ChCl–urea molar ratio of 1:3, moisture content of 60%, liquid-to-material ratio of 28.5 mL/g, ultrasonic extraction time of 49 min, and temperature of 62 °C. Under these conditions, the extraction rate reached 117.95 ± 5.97 mg/g, a 73.5% improvement compared with 80% EtOH extraction. The comparison of the two algorithms showed that RSM (R = 0.9981, RMSE = 0.6570) had better fitting accuracy and prediction stability under small sample conditions than MLP (R = 0.9427, RMSE = 5.261) and RF (R = 0.9431, RMSE = 5.2442). DFT (density functional theory) analysis demonstrated that hydrogen bonds, Van der Waals forces, and cation–π interactions mediate the interaction between NADES-13 and flavonoids. Ultrasonic cavitation-induced cell wall damage and the hydrogen-bond network of NADES-13 were confirmed separately by SEM (scanning electron microscopy) and FTIR (Fourier transform infrared spectroscopy). In vitro experiments showed that the extract possessed concentration-dependent antioxidant activity and strong antibacterial activity, with an inhibition rate of 96.87 ± 5.09% against Escherichia coli at a concentration of 0.04 mg/mL. In this study, a “Smart Optimization–Molecular Mechanism–Activity Verification” green extraction system was developed, which offers an efficient and environmentally friendly strategy for extracting plant bioactive components and contributes to the progress of green chemistry.