Title : Phytochemical profiling, antibacterial activity and antibiofilm activity of wild Tunisian rosemary (Rosmarinus officinalis L.) and thyme (Thymbra capitata L.) essential oils against pathogenic bacteria
Abstract:
The excessive use of antibiotics in several fields, such as agriculture, food and pharmaceutical industries and medicine leads to the emergence of multi-resistant bacteria and the evolution of antimicrobial resistance genes with serious consequences on environment and human health. The bacteria adopted many drug-resistance strategies such as drug molecules inactivation, mutant proteins synthesis, and biofilm production. Therefore, controlling bacteria biofilm formation’s still a challenging issue that requires discovery and development of effective and safe alternative antimicrobials that may be used for the prevention of antibiotic resistance and infection recurrence. In fact, aromatic and medicinal plant essential oils have been used for thousands of years as natural medicines to fight against a multitude of pathogens, such as bacteria, fungi and viruses. Rosemary (Rosmarinus officinalis L.) and Thym (Thymbra capitata L.) essential oils have been used in food, pharmaceutical, cosmetics, and industries. Indeed, these oils have several biological properties: antioxidant, antibacterial, antifungal, antiviral and antibiofilm. The present study was conducted to investigate the phytochemical composition, to evaluate the antibacterial activity and anti-biofilm effect of Tunisian wild rosemary and thyme essential oils (REOs and TEOs). The phytochemical composition was analyzed by GC-MS. The antibacterial activity, evaluated by disc diffusion and micro-dilution method, and the anti-biofilm activity assessed using a crystal violet test, were tested against two Gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis) and two Gram-negative strains (Escherichia coli and Salmonella typhimurium). GC-MS analysis revealed thirty-one compounds in REOs. The main components that define the chemotype were eucalyptol, α-pinene and camphor (48.98, 13.84 and 6.22, respectively). For TEOs, twenty compounds were identified in which represent 99.8% of the oil. The main component of the TEOs that define the chemotype was carvacrol (85.41%). The inhibition zone diameter values were determined and the results showed that all the tested REOs showed a strong activity against all bacterial strains. The minimum inhibitory concentration (MIC) varied between <0.97 and 1.95 and the minimum bactericidal concentration (MBC) ranged from 0.97 to 15.62 μL/mL. Moreover, the studied REOs showed potential anti-bifilm activities. The percentages of inhibition varied from >50% to more than 90%. Similarly, in the eradication activity, the majority of the tested REOs were able to eradicate the bacterial preinstalled biofilms with rates attending 92%. Furthermore, the studied TEOs exhibited interesting antibacterial activity against all tested bacterial strains. Also, the studied TEOs showed potential anti-biofilm activity. The percentages of inhibition varied from 57.92% to 83.72%. Similarly, in the eradication activity, the tested TEOs were able to eradicate the bacterial preinstalled biofilms with rates attending the 88.41%. Overall, the results demonstrate that REOs and TEOs present strong antibacterial and antibiofilm activities and could be, explored for food pharmaceutical and cosmetics industries with appreciable human health-promoting properties.
Key words: Rosemary (Rosmarinus officinalis L.), Thyme (Thymbra capitata L.), Essential Oils, Phytochemical Profile, Pathogenic Bacteria, Antibacterial Activity, Antibiofilm Effect.
