Variation of thymol, carvacrol and thymoquinone production from wild and cultivated Origanum syriacum of South Lebanon

Essential oils from wild and cultivated Origanum syriacum were prepared monthly by hydrodistillation. Their composition in thymol, carvacrol and thymoquinone were studied byGas chromatography–mass spectrometry (GC-MS). Essential oils extraction ranged from 3.82 and 3.44% in February to 8.4 and 6.8% in may, from cultivated and wild samples respectively. The essential oil composition for all samples was dominated by carvacrol. The cultivated populations harvested in April just before flowering had a higher peak content in thymol (31.5%) and carvacrol (49.8%). Thymoquinone was detected in traces only in February, and was not found in any other population studied from O. syriacum of South Lebanon.   Key words: Origanum syriacum, essential oil, carvacrol, thymol, thymoquinone.