Composition, antimicrobial, antioxidant, and antiproliferative activity of Origanum dictamnus (dittany) essential oil

BACKGROUND Nowadays, there has been an increased interest in essential oils from various plant origins as potential antimicrobial, antioxidant, and antiproliferative agents. This trend can be mainly attributed to the rising number and severity of food poisoning outbreaks worldwide along with the recent negative consumer perception against artificial food additives and the demand for novel functional foods with possible health benefits. Origanum dictamnus (dittany) is an aromatic, tender perennial plant that only grows wild on the mountainsides and gorges of the island of Crete in Greece. OBJECTIVE The aim of the present study was to investigate the antimicrobial, antioxidant, and antiproliferative properties of O. dictamnus essential oil and its main components and assess its commercial potential in the food industry. DESIGN O. dictamnus essential oil was initially analyzed by gas chromatography-mass spectrometry (GC-MS) to determine semi-quantitative chemical composition of the essential oils. Subsequently, the antimicrobial properties were assayed and the minimum inhibitory and non-inhibitory concentration values were determined. The antioxidant activity and cytotoxic action against the hepatoma adenocarcinoma cell line HepG2 of the essential oil and its main components were further evaluated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and by the sulforhodamine B (SRB) assay, respectively. RESULTS The main constituents of O. dictamnus essential oil identified by GC-MS analysis were carvacrol (52.2%), γ-terpinene (8.4%), p-cymene (6.1%), linalool (1.4%), and caryophyllene (1.3%). O. dictamnus essential oil and its main components were effective against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Listeria monocytogenes, Salmonella Enteritidis, Salmonella typhimurium, Saccharomyces cerevisiae, and Aspergillus niger. In addition, the estimated IC50 value for the DPPH radical scavenging activity for O. dictamnus essential oil was 0.045±0.0042% (v/v) and was mainly attributed to carvacrol. The EC50 value for the essential oil in the 72h SRB assay in HepG2 cells was estimated to be 0.0069±0.00014% (v/v). Among the individual constituents tested, carvacrol was the most bioactive compound and accounted for the observed antiproliferative activity of the essential oil. CONCLUSIONS The results revealed that O. dictamnus essential oil is a noteworthy growth inhibitor against the microbes studied. It also possesses significant antioxidant activity and demonstrated excellent cytotoxicity against HepG2 cells. Taken together, O. dictamnus essential oil may represent an effective and inexpensive source of potent natural antimicrobial agents with health-promoting properties, which may be incorporated in food systems.