Synergistic interactions of cinnamaldehyde in combination with carvacrol against food-borne bacteria

In order to select effective and safe natural antibacterial ingredients, more than 30 kinds of plant extracts were selected for their suitability as antibacterial agents. A standard broth microdilution method was used to evaluate their antimicrobial activity, a cytotoxicity test was used to detect their safety, and a synergy assay was used to determine which combinations have a synergistic effect. Then time-kill curves were used to further verify their bactericidal capacity. As a result of these tests, cinnamaldehyde and carvacrol were identified first, then subsequently verified to be the most effective and safe natural active substances. It was found that all of the tested bacteria strains were sensitive to cinnamaldehyde and carvacrol. The combination of cinnamaldehyde with carvacrol also showed good synergistic antibacterial effect against 7 of the 11 tested bacterial strains. The time-kill assay verified synergism for the cinnamaldehyde/carvacrol combination toward Escherichia coli and Staphylococcus aureus. These results indicated that the combination of cinnamaldehyde and carvacrol may serve as a promising naturally sourced food preservative with excellent bactericidal activity against common food spoilage microorganisms.