Antimicrobial and Antibiofilm Activity of Origanum vulgare Extracts Obtained by Supercritical Fluid Extraction Under Various Extraction Conditions

Sustainable management of agri-food product safety presents a major challenge requiring extensive action to ensure food safety and consumer health. The pursuit of environmentally friendly solutions that will constitute an alternative to the chemical compounds commonly used in agriculture and the food industries is one of the most important problems. One solution is plant extracts containing various biologically active compounds and exhibiting antimicrobial activity. This study aims to determine the biological activity of extracts obtained from Origanum vulgare L. (leaves) by supercritical CO2 (SC-CO2) extraction using different reaction conditions and compositions. In vitro studies revealed antimicrobial activity against selected bacteria (including Salmonella Enteritidis, Listeria monocytogenes, and Staphylococcus aureus) and fungi (Fusarium spp.), depending mainly on the microorganism species; however, extraction conditions also influenced these properties. The microscopic observations established by optical and fluorescence microscopy showed the changes in the fungal cell’s viability and morphology. There was no observed significant release of intracellular material as stated based on ICP-MS analysis of sodium and potassium concentration. Antibiofilm properties of extract obtained by extraction at 40 °C were also demonstrated against S. aureus, P. aeruginosa, and L. monocytogenes, with stronger properties observed against Gram-positive bacteria. Phytochemical characterization of the extracts was determined using a liquid chromatography system with an orbitrap mass spectrometer (LC/MS), identifying, i.e., phenolic acids: protocatechuic, hydroxybenzoic, caffeic, and rosmarinic; flavonoids: luteolin, naringenin, and kaempferol; and terpenoids: oleanolic and ursolic acids.