Antimicrobial activities of some medicinal essential oils
In this study, the antimicrobial properties of essential oils obtained from Coriandrum sativum, Foeniculum vulgare Miller, Salvia triloba, Laurus nobilis L., Citrus limon and Origanum smyrnaeum L. were investigated. A total of eight microbial organisms belonging to six species of bacteria, namely Salmonella typhimurium, Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Escherichia coli and Enterobacter aerogenes, as well as two fungi, Candida albicans and Aspergillus niger, were studied using a disc-diffusion and agar dilution (minimal inhibition concentration) method. The antimicrobial activity of essential oils obtained from the six plants turned out to be more effective in the case of bacteria than against fungi. The antimicrobial activity against Gram-positive bacteria was more pronounced than against Gram-negative ones. All the investigated plants are known as having healing properties and are used to treat various diseases. The essential oils obtained from L. nobilis and O. smyrnaeum showed the highest antifungal activity against C. albicans and A. niger, while the essential oils obtained from F. vulgare showed the highest antimicrobial activity against P. aeruginosa and E. coli. On the other hand, the essential oils obtained from O. smyrnaeum showed stronger antibacterial activity in the case of E. aerogenes and S. aureus, but were not equally effective against E. coli. The other crude essential oils showed varied levels of antibacterial and antifungal activity. The minimal inhibition concentrations (MIC ) of the essential oils obtained from O. smyrnaeum and of those obtained from L. nobilis ranged from 1.17 to 4.71 mg/ml, and 2.4 to 19.2 mg/ml, respectively.