Antibacterial and Antiviral Activities of Essential Oils of Northern Moroccan Plants

Aims: This study was designed to evaluate the antimicrobial activity of five essential oils (EOs) extracted from the aerial parts (leaves and flowering tops) of three species growing in the north of Morocco: Origanum elongatum, Thymus capitatus and Mentha suaveolens.

Study Design: Chemical analysis of EOs, antibacterial and antiviral activities of EOs.

Place and Duration of Study: Department of Biology (Faculty of Sciences), Institute of Agrochemistry and Food Technology (IATA), between September 2009 and December 2009.

Methodology: The EO constituents were extracted by hydrodistillation and analysed by GC-MS. The antibacterial activity of EOs was tested against three reference strains, Salmonella enterica subsp. enterica CECT 915T, Listeria monocytogenes CECT 4031T, and Escherichia coli O157:H7 CECT 4267, and two food isolated strains Salmonella sp. S64 and Listeria monocytogenes L23, using the diffusion method and the microtitration assays. The antiviral effect of EOs was evaluated for the inactivation of murine norovirus (MNV-1), a human norovirus surrogate.

Results: GC and GC/MS analyses revealed that thyme EO predominantly contains carvacrol (58.77-68.63%), p-cymene (4.84-5.63%), γ-terpinene (2.78-3.75%) and β-caryophyllene (2.62-2.91%). Oregano EO was mainly constituted by carvacrol (19.21-40.12%), thymol (3.57-14.24%), p-cymene (16.08-16.19%) and γ-terpinene (7.27-13.48%). While, mint EO was characterized by piperitenone oxide (41.84%), (-)-isopulegol (11.95%) and limonene (7.35%). All extracts exhibited an antibacterial activity at different levels against strains reported as the causal agents of foodborne diseases, but a low antiviral activity (0.87-0.50 log10 TCID50/ml reduction) was observed.

Conclusion: Results suggest the potential use of tested EOs as bio-preservatives in the food industry. However, their antiviral activity needs to be further investigated