Enhancement of the antibiotic activity against a multiresistant Escherichia coli by Mentha arvensis L. and chlorpromazine

Chemotherapy. 2008;54(4):328-30. doi: 10.1159/000151267. Epub 2008 Aug 12.


Background: This is the first report testing the antibiotic resistance-modifying activity of Mentha arvensis.

Methods: In this study an ethanol extract of M. arvensis L. and chlorpromazine were tested for their antimicrobial activity alone or in combination with conventional antibiotics against strains of Escherichia coli.

Results: The growth of two E. coli strains tested was not inhibited by the extract. The minimum inhibitory concentration and minimal bactericide concentration values were >or=1 mg/ml for both strains of E. coli used. A potentiating effect of this extract on gentamicin was demonstrated. Similarly, there was a potentiating effect of chlorpromazine on kanamycin, amikacin and tobramycin, indicating the involvement of an efflux system in the resistance to these aminoglycosides.

Conclusions: It is therefore suggested that extracts from M. arvensis could be used as a source of plant-derived natural products with resistance-modifying activity, such as in the case of gentamicin, constituting a new weapon against bacterial resistance to antibiotics, as with chlorpromazine.

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Chlorpromazine / pharmacology*
  • Drug Resistance, Multiple, Bacterial / drug effects*
  • Escherichia coli / drug effects*
  • Mentha / chemistry*


  • Anti-Bacterial Agents
  • Chlorpromazine