**5. Conclusions**

The EO from *Mentha* × *piperita* cv. 'Kristinka' demonstrated promising antifungal activity against some serious phytopathogenic fungi even at low concentrations and this

result is very interesting, especially for controlling postharvest fungi. In addition, the studied EO showed acceptable antibacterial activity against the following pathogenic bacteria: *P. syringae* pv. *phaseolicola* and *C. michiganensis*; however, it showed little effect against *P. savastanoi,* and no activity against *X. campestris*. On the other hand, the biological activity of the studied EO can be highly attributed to its rich content of menthol (70.08%) and menthone (14.49%). The MFC value of the fungicidal effect achieved by the peppermint EO was 2.9 mg/mL against *B. cinerea* and the MFC value in the case of menthol was 0.8 mg/mL against *M. fructicola*, whereas menthone achieved MFC values equal to 1.3 mg/mL against *M. fructicola* and *B. cinerea*.

The obtained promising results of the antimicrobial activity of peppermint EO proved its potential to control several fungal and bacterial pathogens. Furthermore, the studied EO and its two main constituents can be used successfully in the chemical industries as natural alternatives to synthetic substances against several phytopathogens.

**Author Contributions:** Conceptualization, I.C., D.G. and H.S.E.; methodology, H.S.E., D.G. and I.C.; investigation, I.C. and D.G.; resources, D.G. and H.S.E. data curation, I.C. writing—original draft preparation, H.S.E. and D.G.; writing—review and editing, H.S.E. and I.C. and supervision, I.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.
