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.