Comparative chemical and antimicrobial study of nine essential oils obtained from medicinal plants growing in Egypt

Essential oils are one of interesting natural products group that are used in different aspects of life due to their various biological activities. This study investigate the antimicrobial activities of 9 herbal essential oils on survival and growth of selected pathogenic and spoilage microorganisms. Essential oils were obtained by hydrodistillation method and were analyzed using GC/MS technique. The oils were tested for their antimicrobial activity against 2 Gram +ve, Staphylococcus aureus (S. aureus) and Listeria innocua (L. innocua), 2 Gram −ve, Pseudomonas aeruginosa (P. aeruginosa) and Salmonella Typhi (S. Typhi) as well as 2 Fungi, Aspergillus niger (A. niger) and Candida albicans (C. albicans), using agar dilution method. Minimum inhibitory concentration (MIC) was determined. The antibiotic susceptibility test was performed against the test organisms by disc diffusion method. Results showed that Cinnamon oil was found effective against all the tested strains (MIC ≤ 1 μl/ml). Peppermint, lemon grass, caraway, anise, fennel and clove showed activity at (MIC ≤ 1 μl/ml) with all the tested organisms except for P. aeruginosa. Lavender oil exhibited antimicrobial activities against 4 strains (S. aureus, L. innocua, A. niger and C. albicans) with MIC (≤1 μl/ml) while geranium oil was inhibitory at (MIC ≤ 1 μl/ml) against S. aureus, S. Typhi, A. niger and C. albicans and with MIC ∼ 2 μl/ml against L. innocua. Although Gram −ve organisms had shown high resistance toward different essential oils, they were found to be susceptible to cinnamon oil even at lower concentration. Cinnamon oil is effective against drug resistant organisms. It can be suggested to use essential oils/constituents as potential natural preservatives and would be helpful in the treatment of various infections.