Abstract
The antibacterial activities of peppermint oil and its 53 constituents against Escherichia coil were examined in a preliminary screening test. Peppermint oil and 15 of its constituents had significant bactericidal activity against non-pathogenic E. coil and enterohemorrhagic E. coil O157: H7. Polyphenols from green tea and four catechins from green tea also had antibacterial activity aganist E. coil O157: H7 in liquid culture medium. Peppermint oil and three of its constituents, namely, menthol, menthone and neomenthol, killed the bacteria within one hour at concentrations above 400 μ g/ml in phosphate-buffered saline. Polyphenols from green tea showed bacteriostatic activity in the culture medium, and bactericidal activity in PBS. This latter effect only became evident after several hours. A synergistic effect was observed for peppermint oil and for menthol when combined with green-tea polyphenols. These results suggest that the antibacterial activities of peppermint oil and green-tea polyphenols might involve different mechanisms and combinations of peppermint oil or the active constituents of peppermint oil with green-tea polyphenols might be useful as natural antibacterial agents against E. coil 0157: H7.
