Essential oil composition and antibacterial activity of Thymus caramanicus at different phenological stages

The genus Thymus L., known as „Avishan“ in Persian, is a well known aromatic perennial herb. Among 215 species of this genus grown in the world, 14 species are distributed in Iranian flora [1]. Thymus species are well known as medicinal plants because of several biological and pharmacological properties [2]. Thymus caramanicus Jalas is an endemic species in Iran. Variations in the quantity and the quality of the essential oil of wild populations of Thymus caramanicus at different phenological stages including vegetative, floral budding, flowering and seed set have beem investigated. The essential oils of air dried samples were obtained by hydrodistillation. The yields of oils (w/w %) at different stages were in the order of: flowering (2.5%), floral budding (2.1%), seed set (2%) and vegetative (1.9%). The oils were analyzed by GC and GC-MS [3]. In total 37, 37, 29 and 35 components were identified and quantified in vegetative, floral budding, full flowering and seed set, representing 99.3%, 98.6%, 99.2% and 97.8% of the oil, respectively. Carvacrol was the major compound in all samples. The ranges of major constituents were as follows: carvacrol (58.9–68.9%), p-cymene (3.0–8.9%), γ-terpinene (4.3–8.0%), thymol (2.4–6.0%) and borneol (2.3–4.0%). Antibacterial activity of the oils and their main compounds were tested against seven Gram-positive and Gram-negative bacteria. Their minimum inhibitory concentration (MIC) values were determined. The maximal inhibition zones and MIC values for bacterial strains, which were sensitive to the essential oil of T. caramanicus, were in the range of 15–36mm and 0.5–15.0mg/ml, respectively. The oils showed high activity against all tested bacteria. Thus, they represent an inexpensive source of natural antibacterial substances.

References: [1] Jalas, J. (1982) Thymus, in Flora Iranica. ed. by Rechinger, K. H., Akademische Druck-u Verlagsanstalt. Graz, Austria. No 150, pp 536–538. [2] Zargari, A. (1990) Medicinal Plants. Tehran University Press Tehran, Iran, Vol. 4, pp 28–42. [3] Adams, R. (2001) Identification of Essential Oil Components by Gas Chromatography/Quadropole Mass Spectroscopy. Allured Publishing Corporation, Carol Stream, USA.