Ultrasound-assisted extraction of flavonoids from Artemisia argyi folium using deep eutectic solvents: optimization,...

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.