Allelopathic Potential of Artemisia absinthium and Artemisia vulgaris from Serbia: Chemical Composition and Bioactivity on Weeds

The use of <i>Artemisia</i> species' plant extracts and essential oils, which are rich in bioactive compounds (allelochemicals), could support weed management. This study focused on the chemical analysis and evaluation of the allelopathic potential of plant extracts (PEs) and essential oils (EOs) of <i>Artemisia absinthium</i> and <i>A. vulgaris</i> on the germination and early seedling growth of weeds (<i>Amaranthus retroflexus</i> and <i>Setaria viridis</i>) <i>in vitro</i>. The plant extract from <i>A. vulgaris</i> showed higher antioxidant activity (IC₅₀ = 0.171 ± 0.01 mg/mL) and phenolic content than that from <i>A. absinthium</i> (IC₅₀ = 0.263 ± 0.01 mg/mL). Chlorogenic acid was the most abundant phenol in both extracts. However, <i>A. absinthium</i> contained a higher amount (1.694 ± 0.081 mg/g) and exhibited a stronger inhibitory effect on the germination of <i>A. retroflexus</i> (EC₅₀ = 0.54 ± 0.02%) and <i>S. viridis</i> (EC₅₀ = 1.51 ± 0.07%) compared to <i>A. vulgaris</i>. The dominant components of <i>A. absinthium</i> essential oil were β-thujone (18.9%), cis-ocimene epoxide (7.88%), and bicyclogermacrene (7.04%), while the main constituents of <i>A. vulgaris</i> essential oil included gurjunene (10.41%), cis-crysanthenyl acetate (7.17%), and γ-humulene (6.67%). The lowest EC₅₀ values for <i>A. absinthium</i> essential oil regarding seed germination and seedling length were estimated for <i>S. viridis</i> (0.28 ± 0.48% and 0.03 ± 0.00%, respectively), whereas <i>A. retroflexus</i> was the most sensitive to <i>A. vulgaris</i> essential oil (0.11 ± 0.04% and 0.02 ± 0.00%, respectively). All tested extracts showed allelopathic potential; however, the results indicate that the essential oils had a stronger inhibitory effect than the plant extracts.