Chemical composition and in vitro evaluation of antioxidant and antibacterial activities of the root oil of Ridolfia segetum (L.) Moris from Tunisia

The present work describes the chemical composition and evaluates the antibacterial and the antioxidant properties of root oil from Ridolfia segetum, a traditional medicinal plant widely distributed in Tunisia. The essential oil, analysed by combination of GC, GC/MS and 13C-NMR, was dominated by dillapiole (47.4%) and myristicin (19.2%). The antioxidant potential of the essential oil was evaluated using the 2,2'-diphenyl-1-picrylhydrazyl free radical scavenging method. The phenylpropanoid-rich root oil possesses good antioxidant properties (IC50 = 38 mg mL-1). The essential oil was evaluated for its antibacterial activity using the microdilution assay, resulting in the inhibition of a number of common human pathogenic bacteria as well as of some clinical and environmental isolated strains. The minimum inhibitory concentrations of the essential oil varied between 1.25 and 5 mg mL-1 and the minimum bactericidal concentrations were superior to 5 mg mL-1 of oil for most strains. These results may suggest that the root oil of R. segetum possesses compounds with antibacterial and antioxidant capacities, and therefore can be explored as a natural preservative ingredient in food and/or for pharmaceutical preparations.