Document Type : Research Paper
Authors
1 Hamadan Research Center of Agriculture and Natural Resources, Hamadan, Iran
2 Sari agricultural sciences and natural resources university
3 Department of Rangeland, University of Agricultural Sciences and Natural Resources, Sari, Mazandaran, Iran
4 Research Institute of Forests and Rangeland, Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran
Abstract
Background and objectives: Thymus lancifolius Celak. is one of the exclusive species of thyme genus in Iran, possessing high economic and medicinal value due to its high phenolic compounds. Considering the indiscriminate harvesting from thyme habitats, low production and non-standard quantity and quality of bioactive ingredients due to the high genetic diversity of thyme, the domestication of T. lancifolius Celak. species and its standardization is one of the goals of this study. In this regard, the quantity and quality of this species' essential oil (EO) were investigated and compared in habitat and field conditions.
Methodology: In order to investigate the effects of environmental factors on the quantitative and qualitative production of T. lancifolius Celak. in the field and habitat conditions (five habitats of Rezen, Asadabad, Hamedan, Malayer, and Toyserkan), this species was planted in the Ekbatan station through seed propagation, in the form of a complete randomized block design with three replications. The EO of plants at the full flowering stage were extracted using the hydrodistillation method, and the chemical compounds of EO were measured and identified by GC and GC/MS devices.
Results: The comparison of the EO percentage of T. lancifolius populations shows that there is a significant difference in the habitat, so the Asadabad habitat had the highest EO percentage (3.85%), and the Malayer habitat had the lowest EO (1.94%). The amount of EO of the populations in the field also has a significant difference, so the highest percentage of
EO (4.18%) is related to the Asadabad population and the lowest is related to Malayer (1.78%). In the populations of Asadabad and Toyserkan, the percentage of EO from the field was more than that of the habitat, but in the populations of Razan, Hamedan, and Malayer, the higher EO belongs to the habitat. Compounds in all populations are almost similar in habitat and field conditions but differ in the type of dominant compounds and their amount. The result of the cluster analysis of the important bioactive constituents of the EO in the five studied populations indicates the existence of two types of chemical types (chemotypes), including thymol (chemotype 1) and geraniol/geranyl acetate (chemotype 2) in both field and habitat conditions. In the EO of four populations of T. lancifolius related to chemotype 1, the main compounds include thymol (habitat: 52.2-71.4%, field: 49.4-68.1%), carvacrol (habitat: 4.5-23.5%, field: 3.9-25.5%), p-cemen (habitat: 4.3-6.1%, field: 4.6-6.6%), and γ-terpinene (habitat: 3.9-9.3%, field: 5.7-8.9%). In this chemotype, the highest amount of thymol (71.4%) was observed in the Hamedan habitat, and the highest amount of phenolic compounds (80%) was found in the Malayer habitat. In the Razan population related to chemotype 2, bioactive constituents including geraniol (habitat: 52.1%, field35.8%), geranyl acetate (habitat: 22%, field: 16%), linalool (habitat: 6.3%, field: 14.7%), and thymol (habitat: 7%, farm: 12%) formed the main compounds of the EO.
Conclusion: According to the results of examining the quantity and quality of EO of different populations of T. lancifolius Celak., two main chemotypes, including the thymol chemotype and the geraniol/geranyl acetate chemotype, can be introduced for the domestication and cultivation of this species in Hamadan province to prevent the destruction of thyme plants while using them in the pharmaceutical industry.
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