Supercritical Fluid Extraction of Usnic Acid from Lichen of <Emphasis Type="Italic">Cladonia</Emphasis> Genus

The process of carbon dioxide supercritical fluid extraction (SFE) of secondary metabolites from the lichen of Cladonia genus is studied. The yield of solid extract during SFE with carbon dioxide is significantly higher than during the extraction with acetone, ethanol, and petroleum ether on the Soxhlet apparatus. The maximum content of the target component—usnic acid (UA)—in the extract (91%, yield—2.5% of absolutely dry raw material) is obtained under pressure of 35 MPa, temperature 40°C, and duration of the process of 40 min. Introduction of cosolvents (acetone, ethanol, methylene chloride) to carbon dioxide increases the yield of the target product to 3%.