Confirmation was made using the GC-MS technique, and isolation was done using a preparative HPLC, equipped with an aliquots collector. The microdilution broth susceptibility assay was utilized to determine minimum inhibitory concentrations (MICs). Results: Our in vitro study demonstrated the antibacterial activity

of the Thymus syriacus Boiss essential oil and its components against the tested isolates at levels between 0.375 and 50 µl/ml. The main components of the T. syriacus essential oil were carvacrol, γ-terpinene, and ß–caryophyllene. MIC90 values for the T. syriacus essential oil against the gram-negative organisms varied between 3.125 and Inhibitors,research,lifescience,medical 12.5 µl/ml. The most effective components against the gram-negative bacteria were thymol, carvacrol, dihydro-carvon, and linalool respectively. Conclusions: The T. syriacus essential oil and some of its components exhibited very good inhibitory effects Inhibitors,research,lifescience,medical against Syrian gram-negative isolates. Key Words: Essential oils, Gram-negative bacteria, Minimum inhibitory concentration Introduction Safety testing on essential oils, when used as directed, shows very few bad side effects or risks. Some essential oils have Inhibitors,research,lifescience,medical been approved as ingredients in food and are classified and generally recognized as safe.1 Essential oils should be regarded as one of the several available

feed additives that have been demonstrated to have antibacterial activity against undesirable pathogenic bacteria such as Salmonella spp.2 Essential oils consist of a number of active Inhibitors,research,lifescience,medical compounds, some of them comprising more than 60 individual components that can inhibit the growth of certain microorganisms.3 Besides flavoring, aromatic plants have been drawn upon for their medicinal properties for Inhibitors,research,lifescience,medical centuries.4 As natural products with well-documented

and repeatedly demonstrated efficiency against a wide range of microorganisms, essential oils receive particular attention as agents suitable for prophylactic and medical treatment.5 Many essential oil isolates exhibit inhibitory Bumetanide properties in challenge tests against microorganisms.6 Herbs have been found to possess antimicrobial activity and anti-viral properties.7 The genus Thymus (Bosutinib molecular weight Lamiaceae) consists of more than 300 evergreen species of herbaceous perennials and sub shrubs, native to Southern Europe and Asia.8 This genus is represented by 38 species and altogether 64 taxa.9 The Thymus genus species (Lamiaceae) are well known in Syria, where their common name is Zattar.10 They are native plants and can be found wildly or cultivated in most Syrian provinces, especially in the north-west, coastal, and south-west regions. Five species of Thymus are found in Syria. Thymus syriacus Boiss are used as herbal tea and condiments. Fresh leaves are used for aromatization of home-made jams, candies, and similar confections.