ABSTRACT
This study aimed to determine the chemical composition and antibacterial activity screening of the volatile oil of Thymus Syriacus. The aerial parts of Thymus Syriacus were collected from the summit of Prophet Abel [a place in the countryside of Damascus], which were done in different stages of the plant growth, before and during blossom stage. Every single sample was divided into two sections: In the first section the plant materials was dried and later extracted using water distillation method, whereas in the second section the volatile oil extracted from water distillation method, whereas in the second section the volatile oil extracted from fresh-green plant material with the former extraction method. The output of the extracted oil was determined in the four collected samples of plant material [fresh-green sample before blossoming, fresh-green sample during blossoming, dry sample before blossoming, and dry sample during blossoming] and the extracted volatile oils were analyzed using gas chromatography GC. The antibacterial activities of the extracted volatile oils in Thymus Syriacus samples were screened against two gram negative bacteria: Pseudomonas aeruginosa and Escherichia coli, and against three gram positive bacteria Staphylococcus aureus, Bacillus subtilis and Micrococcus luteus. Disk diffusion method was used to determine the antibacterial activity and the minimum inhibitory concentrations [MICs] of the active volatile oils were tested using agar dilution method, and broth dilution method; and the minimum bactericidal concentrations [MBCs] were tested using broth dilution method. Results showed that, the percentage of the volatile oil in the aerial plant parts almost doubled at the beginning of the blossoming stage when compared with the results during the pre-blossoming stage and drying of the plant materials made rather insignificant rise in the percentage. The main compound of the volatile oil in Thymus Syriacus was no more than the compound of Carvacrol [74%] and the composition of volatile oils was the same in all tested samples, and their antibacterial activities were similar likewise. Staphylococcus aureus was the most sensitive among the bacterial strains, while Pseudomonas aeruginosa was the most resistant bacteria. In addition, the minimum inhibitory concentrations [MICs] using broth dilution method were: Escherichia coli: 1.25 microlitre/ mililitre and Bacillus subtilis, Staphylococcus aureus: 0.3 microlitre/ mililitre, Micrococcus luteus: 0.6 microlitre/ mililitre. In conclusion, this study insure the antibacterial activity of the volatile oil of Thymus Syriacus, which can be acted and used for medical purposes, and as additive preservatives in food