Antimicrobial activity of ethanolic and aqueous extracts of Urtica dioica, Mentha piperita, Plantago lanceolata and Cynara scolymus leaves

Abstract

Natural antimicrobial agents, particularly plant extracts from Urtica dioica, Mentha piperita, Plantago lanceolata and Cynara scolymus, have attracted considerable attention due to their broad biological activity driven by diverse bioactive compounds and synergistic effects. The efficacy of these extracts depends on plant species, chemical composition, extraction method, and solvent, emphasizing the need for systematic evaluation of ethanolic and aqueous extracts as potential alternatives to synthetic antimicrobials. The aim of this study was to determine and compare the antimicrobial activity of ethanolic and aqueous leaf extracts of Urtica dioica, Mentha piperita, Plantago lanceolata and Cynara scolymus. Reliability was ensured through triplicate testing and standardised methodology (well diffusion method, 100 mg/ml concentration), confirming that the results are representative and statistically valid. Findings indicate that ethanolic extracts demonstrated significantly stronger antimicrobial activity than aqueous extracts (p < 0.05), particularly against Gram-positive bacteria (Staphylococcus epidermidis, Bacillus cereus, Enterococcus faecalis) and the fungus Candida albicans, while Gram-negative bacteria (Salmonella enteritidis, Yersinia enterocolitica) were largely resistant except Pseudomonas aeruginosa. Mentha piperita and P. lanceolate ethanolic extracts exhibited the broadest and most potent antimicrobial spectrum, U. dioica and C. scolymus leaves showed weaker activity but remain valuable sources of bioactive compounds.