Antimicrobial and Preservative Activity of Plectranthus amboinicus (Lour.) Spreng, Bacopa monnieri (L.) Wettst, Flueggea leucopyrus Willd., and Cymbopogon citratus (DC.) Stapf Plant Extracts against Some Common Milk Pathogens and Their Biocompatibili

Due to bacterial contamination, natural medicinal preservatives may be an alternative to enhance the quality of milk. Besides, thorough biocompatibility testing is deemed essential before integrating natural extracts into food products. To address this matter, our research focused on evaluating the antimicrobial potential of Plectranthus amboinicus, Flueggea leucopyrus, Cymbopogon citratus, and Bacopa monnieri against prevalent foodborne pathogens, including Staphylococcus aureus, Escherichia coli, Salmonella spp, and Pseudomonas aeruginosa and investigating the efficacy of plant extracts as natural preservatives along with biocompatibility and toxicity assessments. The methanolic extracts of plant materials were used for measuring antimicrobial activity using the agar well diffusion method, Minimum Inhibitory Concentration (MIC) and Minimum bactericidal concentration (MBC) assays. The preservative activity was tested by isolating pathogenic organisms in a sterilized milk medium and toxicity and biocompatibility was assessed using zebrafish embryo and brine shrimp lethality assays. At a concentration of 400 mg/ml, all plant extracts demonstrated notable activity against bacterial strains. B. monnieri at 400 mg/ml exhibited particularly significant effects on S. aureus (30.3 mm ± 0.6), surpassing the positive control, gentamicin (28.3 mm ± 0.6), while also displaying pronounced activity against E. coli. F. leucopyrus, at the same concentration, showed antimicrobial activity comparable to the positive control against both S. aureus (28.0 mm ± 1.0) and E. coli (27.0 mm ± 1.0). However, as there’s weak-mild toxicity in these herbs, prior to consumption, careful consideration of their toxicity and biocompatibility is imperative for ensuring their safe use.