Evaluation of Combined Antibacterial Effects of Eugenol, Cinnamaldehyde, Thymol, and Carvacrol against E. coli with an Improved Method

摘要

In this study, the antibacterial activities of eugcnol, cinnamaldehyde, thymol, carvacrol, and their combinations against E. coli were investigated separately. First, broth marro-dilution assay was adopted to ileter-mine the minimal inhibitory concentration (MIC) of the 4 components. Second, the combination testing was performed using rhequerboard method. Finally, the combined effects were evaluated with an improved method, which was based on the Indices of fractional inhibitory concentration (FIC) and Effect of the Combination (EC) jointly. The results indicated that MICs of the 4 components wen 1600, 400, 400, and 400 mg/K, respectively; treatments with cinnamaldehyde/eugenol, thymol/eugeuol, earvacrol/eugeiiol, and thymol/carvacrol revealed sybergistic effects according to the 2 indices. By means of combination, MIGs of eugenol, ilnnamaldchyde, thymol, and carvaerol decreased to 400,100,100, and 100 mg/L, respectively. Consequently, the negative Impacts of unpleasant smell of these 4 components could be minimized, making it possible to add them to foods as preservatives. In addition, thisrnM proved evaluation method provided a more accurate and comprehensive way to evaluate combined effects.