Anti-Staphylococcal Activities of Rosmarinus officinalis and Myrtus communis Essential Oils through ROS-Mediated Oxidative Stress.

Rosmarinus officinalis and Myrtus communis essential oils (EOs) are well-known for their ethno-pharmaceutical properties. In the present study, we have analyzed the chemical composition of both EOs by gas chromatography-mass spectrometry. Then we assessed their antibacterial, antibiofilm, and anti-virulence actions against the opportunistic pathogen Staphylococcus aureus. The cytotoxic effect of agents tested against this bacterium was investigated by monitoring reactive oxygen-species (ROS) generation and antioxidant-enzyme (catalase) production. Regarding the antistaphylococcal effects, our results showed antibacterial efficacy of both Eos and their combination, where the minimum inhibitory concentrations ranged between 0.7 and 11.25 mg/mL. A combination of tested agents showed the highest anti-hemolytic and anti-protease effects. Additionally, association between EOs displayed more potency against the development of biofilm performed by S. aureus, with percentage of removal reaching 74%. The inhibitory impacts of EOs on S. aureus virulence factors were discovered to be concentration-dependent. Furthermore, our results provide insight on the abilities of R. officinalis and M. communis EOs, as well as their potential in combination, to generate ROS and affect oxidative stress enzyme catalase in S. aureus, leading to their antagonistic effect against this pathogen.

Characterization of Turpentine nanoemulsion and assessment of its antibiofilm potential against methicillin-resistant Staphylococcus aureus.

Turpentine essential oil (TEO) is a commercially available product having application as food additive, due to its ethno-botanical and ethnopharmacological properties. In the present study, we performed chemical composition of TEO by Gas Chromatography-Mass Spectrometry (GC-MS). Further, TEO was nanoemulsified, encapsulated and characterized by droplet size, PDI, Zeta potential and transmittance. The obtained turpentine nanoemulsion (TNE) was investigated for its antibacterial and antibiofilm potentiality against methicillin-resistant Staphylococcus aureus (MRSA), a model biofilm-forming microorganism. Small micellar TEO nanoparticles were succesfully formed with a mean droplet size ranging from 22.52 to 26.54 nm. Thermodynamic stability studies revealed homogeneous dispersion of the droplets size confirming the stability of TNEs. The developed nano-emulsions displayed two fold enhanced antagonistic activity against S. aureus in comparison with TEOs, with minimum inhibitory concentration (MIC) values at 0.039% (v/v) against MRSA. Additionally, TNEs displayed potent antibiofilm activity against MRSA strains with percent biofilm disruption of around 70.83%. Findings from this study validates the phytomedicinal significance of turpentine nanoemulsions and envisage its exploration as a natural and cost-effective strategy against bacterial biofilms in medical and industrial sectors.

Correlation between chemical composition and antibacterial activity of some Lamiaceae species essential oils from Tunisia.

BACKGROUND: Lamiaceae family is one of the most diverse and common plant families in terms of ethnomedicine due to their potential therapeutic effects. The aim of this study is to investigate the correlation between the chemical composition and the antibacterial effect of five essential oils from this family against five reference bacterial strains responsible of nosocomial diseases and foodborne illnesses. METHODS: The commercial essential oils of Tunisian Rosmarinus officinalis, Thymus capitatus, Origanum majorana and Salvia officinalis were analyzed by GC/FID and GC-MS. Essential oils were evaluated for their antibacterial activities by disc diffusion and microbroth dilution methods against five reference bacterial strains: Pseudomonas aeruginosa, Escherichia coli, Salmonella enterica, Bacillus subtilis and Staphylococcus aureus. The inhibition zone diameter values and the twenty major compounds of the selected essential oils were subjected to PCA and HCA analysis. RESULTS: Analysis by GC/FID and GC/MS allowed the identification of ninety-one components representing 96.0 to 98.2% of the total oils. The different component contents varied according to the species. The main components were carvacrol, 1,8-cineole, α-thujone, α-terpineol and α-pinene. The PCA and the HCA of the selected essential oil components and the inhibition zone diameter (IZD) values identified four species groups and subgroups. Each essential oils group constituted a chemotype responsible for their bacterial inhibition ability. Thymus capitatus essential oil showed the strongest antibacterial activity with MBC ranging from 0.73 to 2.94 mg mL- 1. CONCLUSION: Rosmarinus officinalis, Thymus capitatus, Origanum majorana and Salvia officinalis essential oils have shown promising antibacterial activities against reference bacterial strains responsible for nosocomial diseases and foodborne illnesses.

Chemical Characterization of Five Tunisian Eucalyptus Essential Oils Species.

Hydrodistillation of the dried leaves of five Eucalyptus species, E. alba Reinw. ex Blume, E. citriodora Hook., E. paniculata Sm., harvested from Choucha arboreta (region of Sejnane, northwest of Tunisia), E. pimpiniana Maiden from Mjez Elbab arboreta (north east of Tunisia) and E. bicolor A.Cunn ex Hook from Sidi Smail arboreta (center of Tunisia), in March 2017, afforded essential oils in yields varying from 1.3±0.2 to 6.0±0.9 % according to the species. E. citriodora provided the highest mean percentage of essential oil amongst all the species. Analysis by GC (RI) and GC/MS allowed the identification of 138 components representing 84.6-98.7 % of the total oil. The content of the different samples varied according to the species. The main components were citronellol, followed by 1,8-cineole, α-pinene, τ-cadinol, 7-epi-α-eudesmol, trans-pinocarveol, spathulenol, aromadendrene, γ-cadinene and δ-cadinene. The principal components and the hierarchical cluster analyses separated the five leaf essential oils into three groups, each group constituted a chemotype.