Invasive non-native plant species are of ecological concern globally, as they may negatively affect biodiversity, the economy, and human health. At the same time, invasive non-native plants comprise an underutilised biomass that contains valuable natural bioactive compounds, which could find various biomedical applications and potential medicinal uses. In this paper, we aimed to systematically review the published data surrounding four selected invasive non-native plant species in a medical and therapeutic context. The search was conducted using PubMed and PRISMA guidelines, and strict criteria were employed to provide a thorough framework for the study selection process. After rigorous screening of the 53 selected articles, we were able to summarise the main findings and current knowledge regarding the valorisation opportunities for the selected plants in a medical context and to identify research gaps and highlight further research opportunities. Finally, we concluded that the selected invasive non-native plant species may provide valuable services in the biomedical field if the focus of future research is concentrated on their potential applicability in clinical settings. Furthermore, the valorisation of invasive non-native plant species may prove to be a viable strategy for controlling their spread.

Eupatorium cannabinum L. (Asteraceae) is a medicinal plant with incompletely characterized phytochemical and biological properties. This study optimized ultrasound-assisted extraction (UAE) of phenolic compounds from its aerial parts, using total phenolic content (TPC) as the only response, and evaluated the extract in exploratory in vitro assays. A D-optimal design assessed the effects of extraction time, ultrasound amplitude, and ethanol concentration. The regression model showed good fit and predictive ability (R² = 0.979, Q² = 0.798), and ethanol concentration was the dominant factor. The optimum (30% ethanol, 20 min, 40% amplitude) was confirmed experimentally, yielding 31.32 ± 0.58 mg GAE/g dried plant in the liquid extract. The lyophilized optimized extract (OpEU), analyzed separately, contained 64.64 ± 2.64 mg GAE/g dry extract; because the two values are expressed on different mass bases (dried plant vs. dry extract), they are not directly comparable. Luteolin-7-O-glucoside and ellagic acid were the main targeted phenolics in OpEU (UHPLC-PDA). OpEU scavenged DPPH and ABTS radicals (IC₅₀ of 5.59 and 0.83 mg dry extract/mL) and weakly inhibited α-glucosidase, α-amylase, and pancreatic lipase (IC₅₀ of 3.031, 3.553, and 2.665 mg dry extract/mL). It inhibited Staphylococcus aureus, methicillin-resistant S. aureus, Escherichia coli, and Klebsiella pneumoniae only at the highest concentration tested (5.09 mg/mL), but not Enterococcus faecalis or Pseudomonas aeruginosa, and it was not bactericidal. These preliminary results do not support health-related applications, which would require pyrrolizidine alkaloid and toxicological evaluation.