Morphological and phytochemical characteristics of Inula helenium L. in different altitudes of Zanjan region, Iran

In the present study, the effect of altitude on the morphological characteristics and also essential oil content and composition of Inula helenium L. was studied. This plant was collected in the flowering stage in the first half of July 2017 and 2018 in different altitudes of the Zanjan region (from 1200 to 2400 meters above sea level) and the growth traits of plant organs including leaves, stems, flowers, and roots were measured. In autumn, at the end of the annual growth period of the plants, plant rhizomes were harvested to evaluate essential oil content and composition. The Clevenger device was used for 3 hours for essential oil extraction and the GS-MS device was used to identify the constituents of Inula helenium essential oil. The results showed that there were significant differences in all growth traits and essential oil depending on the altitude of the region. Although, the growth traits of Inula helenium such as leaf and stem dry weight, leaf width and length, leaf number, and plant height decreased with increasing altitude, but the rhizome dry weight and diameter, and essential oil content increased with increasing altitude. The essential oil components of I. helenium were changed with increasing altitude so that the content of geranyl acetone, verbanol, α-pinene, isoalantolactone and valencene increased with increasing altitude. Also, the content of α-selinene decreased and no changes were observed in the content of caryophyllene oxide and β-elemene with increasing altitude. In general, the results showed that altitude is an important and influential factor affecting Inula helium's quantitative and qualitative yield.