Ultrasound-assisted supercritical carbon dioxide extraction of lutein from Tropaeolum majus flowers

Lutein is a functional food ingredient that provides vision protection and antioxidant activity. In this study, ultrasound-assisted supercritical CO₂ extraction was developed to extract lutein from Tropaeolum majus flowers. The maximum lutein yield was achieved at 29 MPa, 57 °C, 20 wt% cosolvent, and 0.21 W/mL ultrasonic energy density through optimization using response surface methodology. Compared with conventional supercritical CO₂ extraction, this hybrid technology increased the lutein yield by 14.9 %, with a 16.7 % shorter extraction time under milder conditions. The total antioxidant yield was increased by 50 %, and the specific phytochemical (carotenoids, flavonoids, and ascorbic acid) yields increased by 54.1 %-62.0 %. Furthermore, the developed Sovová and Chrastil models accurately represented the experimental kinetic curves and predicted lutein solubility under various conditions. Ultrasonic assistance was found to enhance mass transfer coefficients and the solubility in supercritical CO₂. In conclusion, this hybrid technique is an eco-friendly and efficient method for extracting lutein from plants.