Abstract
This study explored the chemical composition, antioxidant activity, and total phenol content of aerial parts from 25 accessions of three Achillea species (Achillea wilhelmsii C. Koch, Achillea vermicularis Trin., and Achillea tenuifolia Lam.). The plants were collected from various natural habitats across Iran, encompassing regions such as Central, Western, Southern, Northern, Western, and Northwestern parts of the country. Subsequently, they were grown together under field conditions. The study revealed significant variation in essential oil yields among accessions of A. wilhelmsii, ranging from 0.01 to 0.107%, A. vermicularis with a range of 0.075 to 1.5%, and A. tenuifolia showing a variation of 0.1 to 2%. The study utilized Gas Chromatography-Mass Spectrometry (GC-MS) analysis, revealing 75, 49, and 75 compounds in the essential oils of A. wilhelmsii, A. tenuifolia, and A. vermicularis, respectively. Major components included camphor, 1,8-cineole, anethole, α-pinene, and phytol in A. wilhelmsii, 1,8-cineole, camphor, levo-carvone, and δ-terpinene in A. vermicularis, and β-cubebene, elixene, β-sesquiphellandrene, 1,8-cineole, camphor, and δ-terpinene in A. tenuifolia. The essential oil compositions of A. wilhelmsii and A. vermicularis were predominantly characterized by oxygenated monoterpenes, whereas that of A. tenuifolia was characterized by sesquiterpenes. Cluster analysis grouped accessions into three clusters, with A. tenuifolia forming a distinct group. Principal Component Analysis (PCA) triplot (62.21% of total variance) confirmed these results and provided insights into compound contributions. Furthermore, total phenolic content and antioxidant activity of the accessions of three species were assessed over 2 years. A. tenuifolia exhibited the highest levels in both categories, with statistically significant linear regression between antioxidant activity and total phenol content for A. tenuifolia and A. wilhelmsii. These findings emphasize significant phytochemical diversity within Achillea species, positioning them as promising natural sources of antioxidants. Further exploration and selection of specific accessions within each species are crucial for unlocking their medicinal potential and supporting cultivation and conservation efforts.