Key words: supercritical fluid extraction, secondary lichen metabolites, usnic acid, Cladonia lichen genus, parameters of the extraction process
The process of supercritical fluid extraction (SFE) of secondary metabolites from Cladonia genus lichen with carbon dioxide is studied. The solid extract yield obtained via carbon dioxide extraction exceeds by far that obtained via acetone extraction in a Soxhlet apparatus. The maximum content of the target component — usnic acid — in the extract (91 %, yield — 2.5% of absolutely dry material) is obtained at 35 MPa, 40 °C and the SFE process duration 40 minutes. The product yield can be increased to 3% by the addition of co-solvents (acetone, ethanol, methylene chloride) to carbon dioxide.