Synergistic ultrasound-supercritical CO2 technology for flavonoids extraction from Toxicodendron vernicifluum (Stokes) F. A. Barkley

Toxicodendron vernicifluum (Stokes) F. A. Barkley (TVSB), a conventional industrial tree crop valued for its diverse uses in lacquer production, medicine, and wood. In this study, a coupled technology, namely, ultrasound-assisted supercritical CO 2 extraction (UASCE), was established to acquire flavonoids from TVSB. The maximum total flavonoid content (TFC) obtained was 14.9 ± 0.9 mg rutin equivalent/g dry mass under the optimized parameters (52 °C temperature, 20 MPa pressure, and 0.17 W/mL ultrasonic energy density). Compared to conventional supercritical CO 2 extraction, UASCE achieved 16.7 % shorter extraction time, 20 % lower pressure, 5.5 % reduced temperature, and 20 % reductions in both CO 2 and co-solvent consumption while increasing TFC by 20.2 %, elevating individual flavonoid concentrations by 8.5–66.7 %, and improving extract antioxidant capacity by 10.5 %. Microstructural observations revealed that dense microfissures on samples treated by UASCE facilitated the migration of substantial solute quantities from particle interiors to the matrix surface. A kinetics study showed that the predictions of the Sovová models closely matched the experimental data. Convection actions were confirmed as the primary extraction driving mechanisms. The employment of ultrasound increased the mass transfer coefficients and reduced the constant extraction rate period. The established Chrastil model accurately predicted the solubility of flavonoids for various operational parameters. Ultrasound was shown to efficiently increase the solubility of flavonoids in supercritical fluid and a representative crossover phenomenon was noticed. In summary, UASCE represents an efficient eco-friendly technique for producing high-quality flavonoid-rich extracts. The findings of this study contribute important implications for developing sustainable natural flavonoids production from TVSB. • Flavonoids were obtained by ultrasound coupled with supercritical CO 2 . • The developed hybrid extraction technique outperforms traditional ones. • Experimental kinetic curves correlated well with the established Sovová model. • The actual solubility results showed good agreement with Chrastil model. • Toxicodendron vernicifluum is a potential resource for natural flavonoids.