JAC Advance Access originally published online on April 21, 2008
Journal of Antimicrobial Chemotherapy 2008 62(2):345-348; doi:10.1093/jac/dkn178
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Original research |
Plant phenolic compounds as ethidium bromide efflux inhibitors in Mycobacterium smegmatis
1 Institute of Pharmaceutical Sciences, Department of Pharmacognosy, Karl-Franzens-University of Graz, Universitaetsplatz 4/I, A-8010 Graz, Austria 2 Centre for Pharmacognosy and Phytotherapy, The School of Pharmacy, University of London, 29-39 Brunswick Square, London WC1N 1AX, UK
Received 27 November 2007; returned 30 January 2008; revised 28 February 2008; accepted 1 April 2008
* Corresponding author. Tel: +43-316-3805531; Fax: +43-316-3809860; E-mail: franz.bucar{at}uni-graz.at
Background: One-third of the world's population is infected with the dormant tuberculosis bacillus, and there have been no new antimycobacterial compounds with new modes of action for over 30 years. Extensively drug-resistant tuberculosis is resistant to first- and second-line drugs, which can have severe side effects, and requires the breakthrough of new antituberculotics and resistance-modifying agents. Efflux pumps can cause multidrug resistance and have recently evoked much interest as promising new targets in antimicrobial therapy.
Objectives: The study was performed to set up an ethidium bromide (EtBr) efflux assay in Mycobacterium smegmatis mc2155 for testing plant natural compounds as mycobacterial efflux pump inhibitors (EPIs).
Methods: After determining the MICs of the putative EPIs, they were tested for synergistic effects with EtBr prior to the efflux assay.
Results: We established an EtBr efflux assay in M. smegmatis mc2155. The isoflavone biochanin A exhibited efflux pump inhibiting activity comparable to that of verapamil. The flavone luteolin and the stilbene resveratrol were less active.
Conclusions: A new assay was established to observe the EtBr efflux in M. smegmatis and was applied to evaluate plant phenolic compounds. Our results highlighted that the isoflavonoid biochanin A exhibited better EPI activities than other flavonoids in mycobacteria.
Keywords: isoflavonoids , biochanin A , efflux pumps , mycobacteria