Supercritical fluid extraction of essential oil from Leptocarpha rivularis using CO2

Supercritical CO2 extraction was applied to recover bioactive extract from L. rivularis leaves. A response surface design was applied to study the effects of temperature (38-52 degrees C) and pressure (10.8-19.2 MPa) on extraction yield, which varied from 2.91 to 5.05g/100 g d.s. Extraction yield was affected positively by the temperature (p < 0.01) and negatively by the pressure (p < 0.05). The negative effect of the pressure was attributed by a reflection of the increased repulsive solute-solvent interactions, or by effect of the pressure in decreasing the mass transfer parameters. Based on the response surface analysis, two pressures were selected at 52 degrees C: 10.8 and 19.2 MPa. The extract obtained at 19.2 MPa (0.61 mmol TE/kg) showed higher antioxidant activity than that at 10.8 MPa (0.35 mmol TE/kg). Quantitative analysis by GC-FID showed that the extract with higher antioxidant activity contained all three target terpenoids: alpha-thujone (5.36 mg/g), beta-caryophyllene (3.43 mg/g) and caryophyllene oxide (5.72 mg/g), while only caryophyllene oxide (11.02 mg/g) was found in the low pressure extracts. The yield with supercritical extraction (at 52 degrees C and 19.2 MPa) was 2.2 times higher than with hydrodistillation (2.11 g/100 g d.s.). Furthermore, supercritical extracts displayed higher antioxidant activity than hydrodistilled extract, compared by DPPH assay (0.60 and 0.46 mmol TE/kg, respectively) and bleaching beta-carotene assay (IC50 values of 1.99 and 10.10 mg/mL, respectively). (C) 2015 Elsevier B.V. All rights reserved.