Evaluation of Antimicrobial Activity of Essential Oil and Ethanolic Extract of 10 Medicinal Plants on Rathayibacter tritici and Xanthomonas translucens

Diseases caused by various drug-resistant strains in plants are increasing in many countries, so many efforts have been made to find new compounds as a suitable alternative to chemical drugs and pesticides. In this study, the antimicrobial effect of essential oils and ethanolic extracts of 10 medicinal plants were investigated on Rathayibacter tritici and Xanthomonas translucens.

 Alcoholic extracts of medicinal plants were extracted using a rotary apparatus. Two standard bacteria R. tritici and X. translucens were prepared from Persian Type Culture Collection. The minimum inhibitory concentration and the minimum inhibitory concentration of essential oils and ethanolic extracts of plants used at a concentration of 50 mg/ ml were determined by dilution in liquid medium on pathogens.

Based on the results, the lowest inhibitory concentration of thyme essential oil was 6.25 ppm, which was inhibited by R. tritici, and the lowest concentration of Hypericum perforatum essential oil against X. translucens was 6.25 ppm. The lowest concentrations of essential oils of yew and fennel were 6.25 ppm, which were inhibited by both bacteria. Rubia tinctorum leaf essential oil in a concentration of 6.25 only inhibited R. tritici bacteria. The antibacterial properties of the essential oils of the studied plants were higher than the extract.

Essential oils of yew and oleander were the most effective against R. tritici and X. translucens, followed by thyme and rosemary against R. tritici and herring flower against X. translucens.  Although the clinical use of ethanolic extracts and essential oils of the studied plants seems valuable due to side effects, but for the clinical use of essential oils and extracts, more research should be done on the mechanism of action of effective compounds of these plants on microbial agents.