Background: Essential oils derived from medicinal plants have attracted increasing attention as natural alternatives to synthetic antimicrobial agents, especially in food safety and preservation. Urtica dioica (nettle) and Malva spp. (mallow) are traditionally known for their medicinal properties, yet their combined antibacterial effects remain underexplored. This study investigated the in vitro antibacterial activity of nettle and mallow essential oils, both individually and in combination (1:1 ratio), against ten common foodborne pathogens responsible for spoilage and contamination.
Methods: Essential oils were extracted from U. dioica and Malva spp., then tested alone and in a 1:1 (v/v) combination for their antibacterial efficacy using agar disk diffusion and broth microdilution assays. The tested bacterial strains included Pseudomonas aeruginosa, Streptococcus pyogenes, Alcaligenes faecalis, Serratia marcescens, Salmonella enteritidis, Staphylococcus aureus, Shigella dysenteriae, Listeria monocytogenes, Klebsiella pneumoniae, and Escherichia coli. Gentamicin (10 µg/disk) was used as a positive control. Data were analyzed to calculate the inhibition zone diameter (DIZ), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). All experiments were performed in triplicate (n = 3), and results were expressed as mean ± standard deviation (SD). Statistical analysis was carried out using one-way ANOVA followed by Tukey’s post hoc test to compare differences among treatment groups.
Results: All essential oil formulations showed antibacterial activity, with MIC values for nettle essential oil (NEO) ranging from 1,250 to 5,000 µg/mL and for mallow essential oil (MEO) from 2,500 to 10,000 µg/mL. The 1:1 combination of NEO and MEO retained NEO’s favorable MIC and delivered a lower MBC for K. pneumoniae compared to MEO alone. Across strains, MIC differences were not uniformly significant. For L. monocytogenes, NEO showed equal MIC and MBC (1,250 µg/mL), indicating its bactericidal activity.
Conclusion: Nettle and mallow essential oils possess significant antibacterial activity against key foodborne pathogens. Their simultaneous application yielded additive effects against some pathogens. These findings support the potential of these essential oils as natural antimicrobial agents to be used in food preservation systems, including for antimicrobial packaging and as edible coatings or surface sanitizers.
