Ultrasound-assisted extraction of flavonoids from Artemisia argyi folium using deep eutectic solvents: optimization, mechanistic characterization, bioactivity evaluation, and strawberry preservation applications.

This study presents an efficient and environmentally sustainable technique for extracting flavonoids from Artemisia argyi folium, employing natural deep eutectic solvents combined with ultrasound-assisted extraction (NADESs-UAE). Among the ten DES systems evaluated, the Choline Chloride-Lactic Acid mixture (ChCl-LA, molar ratio 1:1, designated as DES-3) yielded the highest extraction of 93.39  mg of rutin equivalents (RE) per gram of dry weight (DW). This was much higher than the yields obtained with traditional 60% ethanol or water extraction methods. Response surface methodology (RSM) was used to optimize key extraction variables, including water content, extraction time, temperature, and liquid-to-solid ratio. Optimal conditions included 51.5  g/100  g water content, 56  min extraction time, and an extraction temperature of 59 °C. The liquid-to-solid ratio reached 48  mL/g under optimized conditions. Under these conditions, the predicted flavonoid yield was 99.27  mg RE/g DW, whereas the experimental value was 98.71 ± 0.66  mg RE/g DW, confirming the model's reliability. Kinetic investigations demonstrated that the extraction process followed a pseudo-second-order kinetic model, indicating enhanced diffusion-assisted mass transfer under ultrasonic cavitation conditions. Scanning electron microscopy (SEM) analysis revealed that DES-3 induced pronounced cellular disruption, thereby facilitating enhanced flavonoid extraction. Fourier-transform infrared (FT-IR) spectroscopy further confirmed the presence of strong hydrogen-bonding interactions between ChCl-LA and flavonoid compounds. Compared with conventional solvent systems, the ChCl-LA extract exhibited superior antioxidant activity, including DPPH radical-scavenging activity (959.98 ± 9.59  mg Trolox/g DW), as well as enhanced α-glucosidase inhibition (91.8% at 125  μg/mL) and antibacterial activity. Furthermore, treatment with AAF extracts effectively improved strawberry firmness and enhanced POD activity during storage, thereby prolonging strawberry shelf life. Overall, the findings demonstrate that NADESs-UAE represents a promising green extraction strategy for the efficient recovery and practical utilization of flavonoids from Artemisia argyi folium.