Carvacrol and cymene, phenolic compounds naturally present in the essential oil of oregano and thyme, were examined for their antimicrobial activity against Vibrio cholerae (ATCC 14033, VC1, and VC7) inoculated in carrot juice. Carvacrol exhibited a dose dependent inhibitory effect on the bacteria. Although cymene did not have antimicrobial activity against the bacteria, it enhanced the inhibitory ability of carvacrol. At 25 degrees C, the lowest concentrations of carvacrol and cymene required for zero detectable viable count varied depending on bacterial strains; 5 and 5 ppm, respectively, for VC7; 5 and 7.5 ppm, respectively, for VC1; and 7.5 and 7.5 ppm, respectively, for ATCC 14033. This study also examined several factors influencing the antimicrobial activity of carvacrol and cymene against V. cholerae ATCC 14033, including temperature, bacterial cell number, and food substrate. Carvacrol and cymene inhibited the bacterium in carrot juice at 25 C more efficiently than at 15 and 4 C. The doses of both compounds required for zero detectable viable count increased as the number of the bacterial cells in the carrot juice increased. The fat content and the complexity of foods were shown to decrease the antimicrobial activity of the compounds. 0 2010, The Society for Biotechnology, japan. All rights reserved.