Antibacterial Activity and Major Constituents of Some Essential Oils from Aromatic Plants

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The use of natural products such as antibacterial compounds has increased an effort to reduce the prevalence of bacteria, mostly antibiotic-resistant pathogens. The purpose of this study was to assess the variability in chemical components and antibacterial effectiveness of four essential oils (EOs) from aromatic plants: Thyme (Th), Marjoram (Ma), Mint (Mi), and Dill (Di) against some pathogenic bacteria. Gas chromatography-mass spectrometry (GC-MS) techniques were used to determine the majority of oil contents. The disk diffusion technique was performed to test antibacterial activity; subsequently, the modified agar-well diffusion method was used to assess minimum inhibitory concentration for oils. The antibacterial activity performed against the standard strains Staphylococcus aureus (ATCC 29213), Staphylococcus epidermides (ATCC 12228), Enterococcus faecalies (ATCC 29212), Pseudomonas aeruginosa (ATCC 27853), Klebsiella pneumonia (ATCC 700603), and Escherichia coli. All tested essential oils showed effective antibacterial activity, particularly Th-EO which exhibited a strong antibacterial effect where the results showed that Th-EO revealed high activity against all pathogenic strains, and demonstrated a good efficacy against the antibiotics resistant strain P. aeruginosa. The results showed also that Th-EO possesses the greater antibacterial activity than other EOs with larger inhibition zones (40 mm) and lower minimum inhibitory concentrations less than (2.0 mg/ml). The main components of the Th-EO were Thymol, Benzene, 1-methyl-3-(1-methylethyl), and gamma.-Terpinene. According to the results, essential oils may represent a natural forceful source of compounds with applications in the pharmaceutical and food industries.