Optimization of ultrasound-assisted deep eutectic solvent extraction, characterization, and bioactivities of flavonoids from Cercis glabra leaves

This study presents an innovative and environmentally friendly approach for extracting flavonoids from Cercis glabra leaves using ultrasound - assisted deep eutectic solvent extraction (UAE - DESs). Through systematic evaluation of 22 deep eutectic solvent (DESs) formulations, choline chloride-levulinic acid (ChCl:Lev) was identified as the optimal solvent system. Response surface methodology optimization revealed ideal extraction parameters: a liquid - solid ratio of 25:1 mL/g, extraction temperature of 40 °C, time of 39 min, achieving a flavonoid yield of 8.01 mg/g. Compared with the conventional method (80 % ethanol), UAE - DESs exhibited an extraction efficiency increase of 1.31 - fold. Additionally, the infrared spectrum, viscosity, conductivity, and polarity of the deep eutectic solvent were measured, and its recycling was investigated. The extraction mechanism was elucidated through a synergistic investigation of extraction kinetics models, molecular dynamics simulations, and intermolecular interaction analysis, revealing that hydrogen bonding is a key driving force in the extraction process. Bioactivity assessments demonstrated significant pharmacological potential of the extract, with potent antioxidant capacity. The crude Cercis glabra flavonoid extract (CCEF) exhibited inhibition rates of 92.74 ± 0.74 %, 41.90 ± 0.90 %, and 20.49 ± 0.31 % against DPPH, ABTS, and PTIO radicals, respectively. Additionally, the extract exhibited significant inhibitory effects against tyrosinase (41.90 ± 0.91 %), α - glucosidase (57.45 ± 0.21 %), and acetylcholinesterase (64.42 ± 0.31 %) at 1 mg/mL. Furthermore, seven flavonoid compounds were isolated from the C. glabra flavonoid extract, and their pharmacological activities were determined, further confirming the biological activity of the extract.