Essential Oils of Six Achillea Species: Chemical Profiles, Antimicrobial Potential and Toxicity toward Crustaceans

This is the first comparative study on antimicrobial activity of essential oils (EOs) of six Achillea species (A. crithmifolia, A. distans, A. grandifolia, A. millefolium, A. nobilis, and A. lingulata) against ATCC and clinical microbial strains isolated from human swabs and on their toxicological potential on crustaceans. Oxygenated monoterpenes represented the major compound class in all six EOs, ranging from around 50 % (A. millefolium, A. nobilis, and A. lingulata) up to over 80 % (A. crithmifolia and A. grandifolia). Specific phytochemical profiles of the major volatiles were determined for each species. Still, borneol was the dominant compound in EOs of three yarrow species: A. distans, A. lingulata, and A. millefolium. Other major compounds were 1,8-cineole in A. crithmifolia, camphor in A. grandifolia, and artemisia ketone in A. nobilis EO. Antimicrobial activities of EOs were examined by a microdilution method revealing inhibitory action against all 15 studied strains in the range of 0.07-20.00 mg/mL (MICs). High toxicity (LC₅₀ <100 μg/mL) in Artemia salina acute toxicity bioassay was a shared characteristic, appearing in five out of six tested EOs, i. e., those isolated from A. lingulata, A. millefolium, A. distans, A. nobilis, and A. grandifolia. In both types of biological tests, A. lingulata EO has shown the highest and A. crithmifolia EO the lowest potential. The strongest activities, recorded for EO of A. lingulata, which was the only studied species from the section Anthemoideae, may be explained by its somewhat unusual chemical composition. According to the obtained results, the second dominant compound of this EO is γ-palmitolactone, which may be a significant agent regarding the antimicrobial activity and toxicity to crustaceans, either on its own or in union with other components, and it may be a suitable topic for further research.