Ultrasound-assisted natural deep eutectic solvents extraction of flavonoids from Hippophae rhamnoides: Optimization and kinetics studies

Flavonoids are important bioactive components in Hippophae rhamnoides. In this study, flavonoids were extracted from H. rhamnoides leaves with an ultrasonic-assisted natural deep eutectic solvent. The optimal conditions included a molar ratio of 1:3, a liquid–solid ratio of 40 mL/g, and an extraction time of 30 min, and the extraction yield was 18.70 % ± 0.25 %. A model of the kinetics was developed to describe the extraction of flavonoids using Fick's law as the basis, where the rate constant and diffusion coefficient increased with the temperature, highlighting the pronounced influence of the temperature on the extraction efficiency. Following simulated digestion, the bioaccessibility index showed that 78.21 % of the flavonoids could be absorbed by tissues. These results will be beneficial for achieving the efficient extraction of flavonoids and the full exploitation and utilization of sea buckthorn resources.