In vitro susceptibility of Microsporum spp. and mammalian cells to Eugenia caryophyllus essential oil, eugenol and semisynthetic derivatives.

Background: Microsporum spp. are keratinophilic dermatophytes that mainly invade the stratum corneum of the skin and hair causing clinical symptoms associated with tinea. Its treatment has several limitations, and the search for new active molecules is necessary.
Objective: To evaluate the antifungal and cytotoxic potential of Eugenia caryophyllus essential oil (EO), eugenol, isoeugenol and methylisoeugenol against Microsporum canis, M. gypseum and Vero cells.
Methods: The EO was extracted by conventional heating-assisted hydrodistillation, the eugenol obtained commercially and the derivatives through Williamson synthesis. Minimal inhibitory concentration (MICs), minimum fungicidal concentration, inhibition of radial mycelial growth and germination inhibition were used to evaluate the antifungal activity. In addition, a colorimetric test was conducted to evaluate cytotoxic activity.
Results: MIC and MFC values for all compounds were 62.5-500 μg/mL for both of the species of Microsporum evaluated. Also, concentrations of 300 μg/mL of the compounds inhibited 100% of M. canis mycelium. The inhibition of germination was observed after 6 hours of treatment (11.86 ± 3.46-85.31 ± 0%). No cytotoxicity was observed in Vero cells (CC ₅₀  > 105 μg/mL), whereas terbinafine showed CC ₅₀ 31.00 ± 0.61 μg/mL.
Conclusions: Our study indicates an interesting bioactivity of isoeugenol and methylisoeugenol against M. canis, M. gypseum and mammalian cells.
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