Combination of ultrasound and supercritical carbon dioxide extraction for trigonelline production from Quisqualis indica

Trigonelline is a natural alkaloid with important nutrient benefits. A hybrid technique adopting ultrasound-assisted supercritical CO₂ extraction (UASCE) was exploited for extraction of trigonelline from Quisqualis indica. Response surface methodology was used to optimize operational parameters of the UASCE process, which indicated that the highest trigonelline yield (TY), 4.22 ± 0.06 mg/g dry mass, reached at 62 °C temperature, 26 MPa pressure, 13.5 wt% co-solvent concentration, and 0.16 W/mL ultrasonic energy density. When compared to traditional supercritical CO₂ extraction, UASCE yielded higher TY more quickly while using milder operational conditions and producing higher antioxidant capacity and concentrations of phytochemicals (alkaloids, flavonoids, triterpenoids) of the extract. Microstructural observation showed that the extensive micro-fractures formed in UASCE-processed samples may have positive effects on solutes liberation. Furthermore, a kinetic study revealed that the developed Sovová models matched with the measured results. The extraction impetus was derived primarily from convection mechanism. Ultrasound increased extraction rates and mass transfer coefficients and shortened the characteristic extraction periods. Additionally, a correlated Chrastil equation was developed for determination of solubility under varying extraction conditions. The Chrastil model reflected actual solubilities of trigonelline satisfactorily and a typical crossover solubility phenomenon was observed. Ultrasound can effectively promote the solubility of trigonelline in supercritical CO₂. In conclusion, UASCE is a sustainable and high-performance procedure to produce high-quality trigonelline-rich extracts. This paper provides new work about industrial production design of trigonelline for the future. Furthermore, Quisqualis indica serves as a prospective natural source for trigonelline acquisition.