Experimental optimization of the supercritical fluid extraction of triterpenoids from Acacia dealbata Link. Leaves

Abstract

Acacia dealbata Link. is an invasive species with a negative impact on forest production areas. Its removal generates large amounts of residues (biomass) that can be burned for energy production or extracted to obtain high-value compounds, such as triterpenoids of the lupane, ursane and oleanane families, with known bioactive properties. The extraction can be performed with conventional organic solvents or by supercritical fluid extraction (SFE) with CO 2 which is a greener alternative. In this work, SFE of A. dealbata Link. leaves was studied in order to identify and optimize the SFE parameters (pressure: 200–300 bar; temperature: 313.15–353.15 K; and addition of ethyl acetate as cosolvent: 0–10 wt%) that enhance productivity and selectivity towards specific triterpenoids. Even though Soxhlet extraction with dichloromethane provided higher total extraction yield ( η T o t a l = 3.8 wt% versus 2.1–3.2 wt%, for SFE), SFE surpassed Soxhlet results in terms of individual yields and concentrations of squalene , α-tocopherol, α-amyrone, β-amyrone, and lupenone. For these five compounds the SFE yield reached 0.8043 wt% and the extract concentration reached 35.5 wt% (15.1 % and 95.1 % higher than with Soxhlet extraction, respectively). Particular emphasis should be given to lupenone, with a maximum yield of 0.4748 wt% and a concentration of 22.9 wt% in the SFE extracts obtained at 250 bar, 313.15 K and no cosolvent (ethyl acetate). The optimum conditions of pressure, temperature and ethyl acetate content depended on the response. Productivity, η T o t a l , was maximized by increasing all three factors to its maximum conditions. Temperature was one of the most impactful parameters on the individual triterpenoids SFE yields with lower temperatures enhancing the selectivity.

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