Comparative study of chemical compositions and antimicrobial effect of different genius of Thymus harvested during two period of development

The essential oils obtained by steam distillation of the aerial parts of Thymus taxa collected before and during the flowering period in different region of eastern Algeria, were analyzed by gas chromatography coupled with mass spectrometry (GC-MS). The extraction yields of essential oils of T. numidicus species are 1.28 % during pre-flowering. This yield is better during the flowering period with 2.85%. T. algeriensis gave extraction yields 1.156 % and 1.79 % in the two periods respectively. T. ciliatus produced oil with yields of 1.002 % before flowering and 1.79 % during flowering. Chromatographic analysis (GC-MS) showed that these essential oils are rich with oxygenated monoterpene compounds with 54.07 % and 80.37% of the composition for T. ciliatis, 61.86 % and 73.02 % for T. algeriensis, 54.48 % and 77.56 % for T. numidicus, corresponding to the two periods mentioned above respectively. The antimicrobial activity was tested against 3 gram positive and gram negative bacterial by the use of the disc diffusion method. The thymus taxa have shown great sensitivity. The three essential oils are effective against Escherichia. coli 22, while essential oil of T. ciliatus obtained before flowering and essential oil of T. numidicus in flowering period are most effective against Staphyllococcus 23.