Studies on bacterial efflux pump inhibitors and their distribution in land plants

Multiple plants have been identified in the literature that inhibit bacterial toxic compound efflux pumps, thus synergising the activity of antimicrobial compounds.  This phenomenon is relevant to the study of traditional botanical medicine, adding explanatory information to the use of plants in combination remedies and to observations of antibacterial medicinal plant extracts being more active than antimicrobials purified from them. This study sought to develop improved methods for the study of this phenomenon, and to determine its prevalence in land plant lineages.  Two improved assays were developed, including a mass spectrometry-based protocol which was successful in quantifying the efflux pump inhibitory activity of a wide array of plant extracts and pure compounds. These data showed that the production of efflux pump inhibitors is more widely distributed in land plants than the previous literature suggests; further, this prevalence is linked in part to the presence of flavonoids.