121 0009-3130/10/4601-0121  2010 Springer Science+Business Media, Inc. Chemistry of Natural Compounds, Vol. 46, No. 1, 2010 CHEMICAL COMPOSITION OF THE ESSENTIAL OILS FROM Thymus transcaspicus IN NATURAL HABITATS L. Tabrizi, 1* A. Koocheki, 2 P. Rezvani Moghaddam, 2 UDC 547.913 and M. Nassiri Mahallati 2 Thymus from Lamiaceae contains different species with variable chemical constituents 1. Due to interspecific hybridization, the number of species from this genus is reported to be 350 2 with 14 species from Iran 3. The genus Thymus have been widely used in folk medicine in the world and also in medicinal and nonmedicinal aspects in the food, pharmaceutical, and cosmetic industries as a flavoring agent (condiment and spice), culinary herb, and herbal medicine in the treatment of a variety of illnesses 2, 4, 5. These species are rich in monoterpenoid phenols, which contain important constituents such as thymol and carvacrol. The ecological role of secondary metabolites in Thymus can be associated with adaptation to the environment and interactive competition with other plants and also a chemical defense against herbivory and plant pathogens. There is evidence indicating the importance of the diversity of monoterpenes as an adaptation strategy to different environments 2. There is evidence on the antifungal 6, antibacterial and antiparasitic 7, 8, antioxidant 9, 10 and antispasmodic 2, 11 activities from chemical extracts of Thymus genus. Thymol, carvacrol, p-cymene, and -terpinene are the main constituents of the Thymus genus 12–15. Khorasan thyme (Thymus transcaspicus Klokov) 16 is native to Iran and Turkmenistan with a limited distribution in the Northeast of Iran from 1700 to 2800 m altitude 17, 18. Although this species is native to Iran, there is not much information on the chemical composition, particularly its essential oil constituents. Miri et al. 19 reported 56.4% thymol, 7.7% -terpinene, 7.6% carvacrol, and 6.3% p-cymene from this species. The purpose of the present investigation was to analyze the chemical constituent of plant material from T. transcaspicus in different habitats in Khorasan, Northeast of Iran. Table 1 shows that the range of essential oils was from 1.2% to 2.3% in different habitats, with the highest in Tiwan (2.3%). In general, 51 constituents were identified in the essential oils (Table 1) with 43 (representing 100% of the total amount) in Reiin, 36 (representing 96.3% of the total amount) in Pakotal, 43 (representing 99.4% of the total amount) in Laeen Kohneh, and 40 (representing 99.0% of the total amount) in Tiwan. Thymol and carvacrol were the main constituents. This has also been reported elsewhere 20. The thymol content for Pakotal, Laeen Kohneh, and Reiin were 54.3, 45.3, and 44.9%, respectively, and these values were 8.4, 13.1, and 13.3% for carvacrol. However, the trend was somehow different for the Reiin habitat where the content of carvacrol and thymol were 47.3 and 5.3%, respectively. The borneol content for this area was 7.1%. Based on these findings, two distinct chemotypes were recognized, where the thymol chemotype was from Pakotal, Laeen Kohneh, and Tiwan, and the carvacrol chemotype was from Reiin. These differences can be associated with the probable hybridization of different species in the area. This has also been reported in the literature 21. Pluhar et al. 22 studied the essential oil variability of T. pannonicus and T. praecox growing wild in natural habitats and reported that the most common chemotype of T. pannonicus was thymol/p-cymene, while for T. praecox a geraniol/germacrene D/-caryophyllene chemotype was also recorded. The thymol concentration was positively correlated with humus and Na, K, Mg, and Cd contents of the soil. 1) Department of Horticultural Science, Faculty of Agriculture, University of Tehran, Karaj, 31587, Iran, fax: +98 261 224 87 21, e-mail: Leila81152@yahoo.com; 2) Department of Agronomy, Faculty of Agriculture, Ferdowsi University of Mashhad, P. O. Box: 91775-1163, Mashhad, Iran. Published in Khimiya Prirodnykh Soedinenii, No. 1, pp. 103–105, January–February, 2010. Original article submitted July 10, 2008.