The detection of antibacterial actions of whole herb tinctures using luminescent Escherichia coli.

Two whole cell Escherichia coli luminescent biosensors were used to determine the antibacterial actions of 16 herbal tinctures. These bioassays can detect genotoxic (strain DPD2794) and general oxidative stress (DE135) events when challenged with antibacterial substances. Many of the herbal tinctures were active against these Gram-negative bacteria, affecting their metabolism without, in some cases, arresting cell growth or causing cell death. Antibacterial activity ranged from undetectable for Curcuma longa, Cinnamomum zeylanicum and Apium graveolens to highly effective against both E. coli strains in the case of Rosmarinus officinalis. Some of the results were unexpected. Althaea officinalis affected microbial metabolism in spite of the lack of literature precedent, and Cinnamomum zeylanicum did not appear to be antimicrobial, as claimed in some literature. It is concluded that studies using luminescent bacterial biosensors can provide important new insights into the potency and modes of the lethal and sub-lethal antibacterial action of whole herbs, and thereby provide crucial evidence for efficacy demanded by modern science and medicine. Copyright (c) 2007 John Wiley & Sons, Ltd.