Antibacterial and biostimulatory activity of urtica magellanica extract on fish pathogenic bacteria and CHSE-214 salmonid cell line

This study evaluated the antibacterial activity and bio-stimulation activity of the nettle (Urtica magellanica) methanolic extract. The leaf extract contained a high polyphenol content (633.394 mg gallic acid equivalence (GAE)/100 g, Folin–Ciocalteu method) and compounds such as gallic, chlorogenic, ferulic, and synaptic acids, quercetin, coumarin, fumaric acid, rutin, kaempferol, and isorhamnetin. Antibacterial effect on Aeromonas salmonicida and Flavobacterrium psychrophilum showed a minimal inhibitory concentration (MIC) of ≤3.0 mg/mL. In contrast, Vibrio anguillarum showed a MIC ≤0.75 mg/mL. Regarding the biological activity of the extract on salmonid CHSE-214 cells, 0.012–0.023 mg/mL reduced their viability by 50%, while 0.375 mg/mL increased their viability to 182%. Thus, U. magellanica methanolic extract demonstrated activity against fish pathogenic bacteria and a dose-dependent effect on CHSE-214 cells. Therefore, considering the demonstrated effect of the extract and its potential interactions within complex systems, in vivo validation of the extract is required to consider it a sustainable strategy against aquatic pathogens.