Phytochemical variations in Stachys lavandulifolia populations and the role of ecological and edaphic factors

Abstract

Geographic location, environmental conditions, and edaphic factors are interconnected, and collectively influence the total content of some plant-based compounds. Mountain tea (Stachys lavandulifolia Vahl) is a perennial plant in the Lamiaceae family, having prominent medicinal properties due to its unique chemical composition. The current research evaluated effective traits that shape the content of essential oil (EO) and phytochemical compounds in S. lavandulifolia populations (P). Samples were collected from 20 different habitats located in the west and northwest of Iran. The results indicated that the Heris (P3) and Sarab (P7) populations exhibited high levels of EOs and phytochemical properties. In the studied areas, principal component and cluster analyses considered environmental factors like climate and soil, thus revealing significant findings. Soil characteristics, including organic matter content, total nitrogen (N), potassium (K), and soil phosphorus (P) content, were identified as the most influential factors, with average annual rainfall following closely. The highest average annual temperatures largely contributed to distinguishing the areas, thus categorizing the habitats into three distinct groups. EO from 20 populations analyzed using GC/MS showed 41 compounds, the most important of which were α-pinene (1.21–33.29 %), α-bisabolol (0.71–53.05 %), and spathulenol (2.8–18.8 %), germacrene-D (1.13–12.18 %), β-phellandrene (0.09–16.72 %), myrcene (1.01–13.34 %), phytol (1.19–10.14 %), and viridiflorol (0.93–6.19 %). Grouping the S. lavandulifolia populations based on their main compounds in the EO divided them into two distinct habitats. The first habitat had eleven S. lavandulifolia populations, whereas the second had nine. Comparison of mean values among habitats showed that the first habitat was superior to the second, regarding sesquiterpene chemical compounds such as spathulenol, viridiflorol, α-muurolol, α-cadinol, and valeranone. The second habitat was more suitable than the first because of higher amounts of monoterpene chemical compounds, such as α-pinene, myrcene, and β-phellandrene. Overall, in this study, Heris (P3), Azarshahr (P4), and Sarab (P7) populations were favorable because of their EO yield and compounds. Our approach to identifying environmental and edaphic cues that shape the EO content, chemotype, or the presence of high amounts of specific compounds can help to select regions for sampling plant material while prioritizing desirable chemical profiles for direct use or in breeding programs.