Antioxidant properties and anti-quorum sensing potential of Carum copticum essential oil and phenolics against Chromobacterium violaceum

The chemical composition, antimicrobial and antioxidant properties of Carum copticum essential oil and its methanolic extract were investigated. Thirteen compounds were identified representing 99.3% of the total oil composition. Oxygenated monoterpenes (53.0%) dominated the C. copticum essential oil with high contents of thymol (51.7 +/- 1.51%), p-cymene (26.9 +/- 1.11%), gamma-terpinene (16.7 +/- 0.76%), and beta-pinene (1.6 +/- 0.15%). In the methanolic extract, the caffeic, gallic, chlorogenic, coumaric and ferulic acids, flavan-3-ols (catechin), flavone (hyperoside), and the flavonol quercetin were identified. Antimicrobial activity of essential oil and the organic extract was tested by disk diffusion and broth microdilution method. The essential oil was effective against the tested bacteria and yeast strains with the highest activity and the MICs and MBCs values were lower as compared to the methanolic extract. The essential oil showed anti-quorum sensing activity against Chromobacterium violaceum, and the IC50 value for violacein inhibition was 0.23 mg/ml. Both the essential oil and the methanolic extract also showed antioxidant activities. The results obtained highlight the potential use of C. copticum as a possible source of antimicrobial and antioxidant compounds to be used both as food flavor and as a broad spectrum antibiotic.