Exploring Chemical Variability in the Essential Oil of <i>Artemisia absinthium</i> L. in Relation to Different Phenological Stages and Geographical Location

The plant essential oils (EOs) play a fundamental role in the adaptation to different habitats and environmental conditions. To verify the influence of these factors on the EO of Artemisia absinthium L., we conducted a pharmacognostic study on this species, collected during both the vegetative (V) and flowering (F) stages, in two different sites: Cogne (Northern Italy) and Ogliastro Cilento (Southern Italy). At the morphological level, only the shape of the leaf was affected, resulting in smaller and more deeply incised leaves in the Ogliastro samples. Considering the EOs, those from Cogne showed oxygenated monoterpenes as the main class of compounds in both non-flowering (63.88%) and flowering (51.63%) stages, while those from Ogliastro had oxygenated sesquiterpenes (42.17%) as the main class of compounds in the non-flowering stage, and monoterpene hydrocarbons (51.05%) in the flowering one. Moreover, the EOs of plants from the two regions showed qualitative differences; that is, elevated concentrations of myroxide and 3,6-dihydrochamazulene were found in both Cogne samples, while camphor and davanone were found in Ogliastro-V and β-myrcene and β-phellandrene were found in Ogliastro-F. Overall, our data highlighted that both geographical locations and phenological stages influence the phytochemical profile of A. absinthium EOs, suggesting optimal harvesting conditions for maximizing certain bioactive compounds.