Ultrasound-Assisted Deep Eutectic Solvent Extraction of Flavonoids from Hovenia dulcis Thunb: Optimization, Phytochemical Profiling, and Antioxidant and Anti-Inflammatory Activity Evaluation

Hovenia dulcisThunb. is a traditional medicinal and edible plant that is widely recognized for its hepatoprotective and hangover-alleviating properties, which are largely attributed to its rich flavonoid composition. The aim of this study was to develop an environmentally friendly ultrasonic-assisted deep eutectic solvent (UAE-DES) extraction method for the efficient extraction of bioactive flavonoids fromHovenia dulcisThunb. A Box–Behnken design (BBD) was employed to systematically optimize the extraction parameters. Under optimal conditions (water content of 36%, liquid-to-solid ratio of 42:1 mL/g, extraction time of 42 min), the extraction yield reached a maximum of 9.09 ± 0.04%. Following purification using AB-8 macroporous resin, the phytochemicals were comprehensively characterized by UPLC-Q-Exactive Orbitrap-HRMS. A total of 12 flavonoids were identified. Bioassays demonstrated that the purified flavonoids exhibited strong, dose-dependent antioxidant activity against DPPH and ABTS radicals in vitro. Furthermore, the extract demonstrated significant anti-inflammatory activity by markedly inhibiting the excessive production of nitric oxide (NO) in RAW 264.7 macrophages induced by lipopolysaccharide (LPS), whilst exhibiting no cytotoxicity within the tested concentration range (0.06–0.96 mg/mL). These findings strongly confirm that the optimized UAE-DES method is a sustainable and efficient strategy for extracting structurally intact and pharmacologically active flavonoids fromHovenia dulcisThunb, highlighting its immense potential for future applications in the functional food and pharmaceutical industries.