The in vitro antibacterial activity of dietary spice and medicinal herb extracts

The in vitro antibacterial activities of a total of 46 extracts from dietary spices and medicinal herbs were investigated by agar-well diffusion method against five foodborne bacteria (Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, and Salmonella anatum). Their total phenolic contents were also evaluated. Many herb and spice extracts contained high levels of phenolics and exhibited antibacterial activity against foodborne pathogens. Gram-positive bacteria were generally more sensitive to the tested extracts than Gram-negative ones. S. aureus was the most sensitive, while E. coli was the most resistant. There were highly positive relationships (R(2)=0.73-0.93) between antibacterial activities and phenolic content of the tested extracts against each bacterium. This suggested that the antibacterial activity of the tested extracts was closely associated with their phenolic constituents.