Thymol, as a dietary monoterpene, is a phenol derivative of cymene, which is the major component of the essential oil of Trachyspermum ammi (L.). It shows multiple biological activities: antifungal, antibacterial, antivirus and anti-inflammatory. T. ammi, commonly known as ajowan, belongs to Apiaceae and is an important medicinal seed spice. To identify the putative genes involved in thymol and other monoterpene biosynthesis, we provided transcriptomes of four inflorescence tissues of two ajowan ecotypes, containing different thymol yield. This study has detected the genes encoding enzymes for the go-between stages of the terpenoid biosynthesis pathways. A large number of unigenes, differentially expressed between four inflorescence tissues of two ajowan ecotypes, was revealed by a transcriptome analysis. Furthermore, differentially expressed unigenes encoding dehydrogenases, transcription factors, and cytochrome P450s, which might be associated with terpenoid diversity in T. ammi, were identified. The sequencing data obtained in this study formed a valuable repository of genetic information for an understanding of the formation of the main constituents of ajowan essential oil and functional analysis of thymol-specific genes. Comparative transcriptome analysis led to the development of new resources for a functional breeding of ajowan.

The essential oil chemotype of an Iranian ecotype of ajowan was identified using gas chromatography mass spectrometry (GC-MS) analysis. Fifteen chemical compounds of essential oils were identified using GC-MS analysis. Thymol, ρ-cymene and γ-terpinen were identified as major components in essential oil of investigated ecotype with 54.32, 21.74, and 19.38 percentages, respectively. Only 0.42 % of the decomposed essential oil was related to carvacrol. Based on the results of the present study, thymol was the predominant composition in the essential oil of investigated ecotype of ajowan and these results can help to purposeful use of this ecotype in pharmaceutical industry, traditional medicine, and other industries.

Essential oil of a native Yarrow (Achillea millefolium) ecotype from Iran was isolated by hydrodistillation from aerial parts and its compounds were identified by gas chromatography. GC/MS analysis was used to investigate thirty-two different essential oil components in this ecotype of which most of them were sesquiterpenes (48.91 %) and monoterpenes (31.22 %). Active components such as caryophyllene oxide, camphor, γ-muurolene, γ-eudesmol, borneol, β-eudesmol, spatulenol, germacrene D and γ-gurjunene were the major compounds in the essential oil of this Yarrow ecotype. The specialized active ingredient and the essential oil profile of Iranian Yarrow make it more valuable for medicine and industry uses.