Phytochemical Variation of the Essential Oils of Different Populations of Thyme (Thymus spp.)

Thyme is one of the medicinal plants that is cultivated in some parts of the world and some of its species are native to Iran. The evaluation of the phytochemical diversity of the essential oil of these species is one of the important steps in the breeding of thyme, and such diversity in essential oil compositions is caused by the different effects of environmental and habitat factors. The present research was carried out in order to understand the phytochemical diversity of the essential oil of different populations of thyme.

In this study, the percentage essential oli compounds in 15 populations (8 populations of T. kotschyanus species, 3 populations of T. migricus, 2 populations of T. fedtschenkoi and a population of T. fallax and T. pubescens) from natural habitats of northwest and west regions of Iran, were studied. In order to evaluate the essential oil percentage and components, flowers of the populations were harvested during flowering season. Identification of essential oil components was performed by gas mass spectrometer (GC/MS) gas chromatography.

A total of 27 compounds were observed in the essential oils of the studied populations, and there was considerable diversity among them. According to the results, Thymol, P-cymene, and Gamma-terpinene were the dominant components of the essential oil. The highest essential oli percentage was related to Thymol taht Bukan- Kouhbardzard (69.75%) and Barugh-Takaghaj (62.13%) had the highest amount. The superiority of West-Azarbaijan populations was significant in Thymol components. In addition, Carvacrol was high in Urmia-Qushchi (58.29%), Sardasht (44.77%), and Linalool was high in Saghez (53.21%) population. By principal component analysis (PCA) it was determined that the first three components explained 60% of the variations in the data. Also, the cluster analysis of the populations of West Azerbaijan province and Kurdistan province was divided into two separate groups. Thymol was negatively correlated with 1,8-cineole. Gamma-terpinene, which was one of the other dominant compounds of the essential oil, with 1,8-cineole and Beta. Ocimene compounds showed a negative correlation. The strongest positive correlation between 1,8-cineole with Beta. Ocimene, Caryophyllene oxide with Camphor, and Lavandulyl acetate with Camphene were observed. Alpha-thujen had the highest negative correlation with other essential oil compounds and Carvacrol did not have a high correlation with other compounds.

Bukan and Barugh case of high amount of Thymol, and Sardasht, Urmia-Qushchi and Naghadeh populations because of their high levels of Thymol and Carvacrol, are superior and can be useful in pharmaceutical industry, products and breeding programs.