Extraction of bioactive compounds from Leptocarpha rivularis stems by three-stage sequential supercritical extraction in fixed bed extractor using CO2 and ethanol-modified CO2

Abstract

Sequential supercritical extraction experiments were carried out in three stages each using CO2 and ethanol-modified-CO2, to improve the extraction yield of bioactive compounds from L. rivularis stems. Four experiments were carried out, each in three stages, combining different levels of temperature (40 or 60 °C) and pressure (20–50 MPa). The increase in pressure and use of a cosolvent increased the total yield of extract and target compounds compared to one-stage extraction. The highest extraction yields of extract (6.29 g/kg d.s.), terpenes (699.9 mg/kg d.s.), flavonoids (741.9 mg/kg d.s.), and alkaloids (6.22 mg/kg d.s.) were obtained in Experiment 4. Sequential extraction of compounds was superior to one-stage extraction using CO2, but inferior when using ethanol-modified CO2. Both sequential and one-stage cumulative extraction curves were modeled, and the effective diffusivity coefficients ranged between 1.51 and 63.3 × 10–13 m2/s, being highest in Stage 3 where the extraction yield was greatest.