Optimization of ultrasound-assisted extraction (UAE) of (poly)phenolic compounds from blueberry (Vaccinium myrtillus) leaves using full-factorial design

In this work, the influence of process parameters (temperature: 25 - 65 °C, ethanol content in the extraction solvent: 30 - 90 vol.%, and solid-to-solvent ratio: 1:15 - 1:45 w/v) on the process of ultrasound-assisted extraction (UAE) of (poly)phenols from blueberry leaves (Vaccinium myrtillus) was investigated. Statistical analysis was performed using the MINITAB 21 software, with the application of three-level full factorial designs. The Responses in the study are the content of total (poly)phenols, flavonoids and anthocyanins in the obtained extracts. The extraction of blueberry leaf was significantly (p < 0.05) impacted by process variables. The R², Adjusted R², and Predicted R² values in the study are high, showing a significant relationship between the independent variables and the Response. The optimal temperature for all three Responses is 65 °C, the optimal solid-to-solvent ratio for total (poly)phenols and anthocyanins is 1:45 w/v and for flavonoids is 28.03 w/v, while the optimal ethanol content in the solvent for total (poly)phenols, flavonoids and anthocyanins is 51.21 vol.%, 50.61 vol.% and 83.33 vol.%, respectively.