Natural plant-derived terpenes: antioxidant activity and antibacterial properties against foodborne pathogens, food spoilage and lactic acid bacteria

The objective of this study was to conduct an in vitro examination of the antioxidant and the antibacterial activities of thymol, carvacrol, linalool, and cinnamaldehyde to evaluate their potential applications in strategies aimed at maintaining food nutritional quality and enhancing food shelf life. The investigation included five common potentially foodborne pathogens (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Listeria monocytogenes, and Salmonella typhimurium), two less-studied food spoilage bacteria (Shewanella putrefaciens and Brochothrix thermosphacta), and four pro-technological bacteria (Lactobacillus plantarum, Lactobacillus rhamnosus, Lactobacillus casei, and Lactobacillus fermentum), associated with food contamination, spoilage, and technology, respectively. Carvacrol and thymol showed the highest antiradical activity, scavenging 50 % of DPPH and ABTS radicals at concentrations in the order of units and hundredths of mmoles/L, respectively. Carvacrol, thymol and cinnamaldehyde showed the highest antibacterial efficacy. Spoilage bacteria (IC_50s=0.35–0.75 mM) were more sensitive than pathogens (IC_50s=0.85–2.35 mM), in particular the highest sensitivity was observed in S. putrefaciens, with IC₅₀ in the order of tenths of mmoles/L. Carvacrol, thymol and cinnamaldehyde resulted in a similar IC_50s in pathogens, except for cinnamaldehyde against P. aeruginosa. In contrast, 90 % inhibition of growth was achieved with the following order of efficacy: cinnamaldehyde>thymol>carvacrol. Lactobacilli exhibited greater resistance compared to that of spoilage bacteria and pathogens. All bacterial strains showed minimal sensitivity (very low % of growth inhibition) to linalool. Due to their antioxidant and antibacterial properties, thymol and carvacrol could be considered as promising phytochemicals for preserving food and extending its shelf life.