Variability in Chemical Composition and Biochemical Activities of Mentha x piperita L. Essential Oil, in Response to Mycorrhizal Symbiosis and Heavy Metal Stress

Abstract The present paper highlights the effect of Pb/Cd‐stress and/or mycorrhizal colonization by Glomus Intraradices on yield, chemical composition, cytotoxicity and antimicrobial activity of Mentha x piperita L. essential oil. Our findings showed that mycorrhizal colonization could be used to improve the essential oil yield of M. x piperita , either in non‐stressed or Pb/Cd‐stressed plants. GC–MS analysis revealed three chemotypes: linalool/pulegone (32.6/30.8 %) chemotype in essential oils of non‐mycorrhizal Pb‐stressed plants, menthone/menthyl acetate (30.3/25.1 %) chemotype in essential oils of non‐mycorrhizal Cd‐stressed plants and menthol (44.6 %) chemotype in essential oils of non‐mycorrhizal non‐stressed plants, mycorrhizal non‐stressed plants and mycorrhizal Pb/Cd‐stressed plants. The cytotoxicity of M. x piperita essential oil, evaluated by brine shrimp lethality bioassay, was increased in presence of Pb/Cd‐stress (from 379.58 to 72.84 μm/mL) and decreased in mycorrhizal plants (from 379.58 to 482.32 μm/mL). The antimicrobial activity of M. x piperita essential oil, evaluated by disc diffusion method and determination of Minimum Inhibitory Concentration against ten microorganisms, was enhanced by the mycorrhizal colonization and deceased by the Pb/Cd‐stress. In conclusion, the inoculation of medicinal plants with mycorrhizal fungi is a real avenue for alleviating abiotic stress and/or increasing the quantity and quality of secondary metabolites in terms of biological activities.