Antifungal activity of eugenol against Botrytis cinerea

The antifungal properties of eugenol were tested against ten plant pathogenic fungal species and detailed studies were conducted regarding in vitro activity of eugenol on Botrytis cinerea. The EC50 value of eugenol on mycelial radial growth of B. cinerea was 38.6 μg/mL; however, eugenol had no bioactivity against conidia germination. B. cinerea hyphae treated with eugenol showed strong propidium iodide fluorescence in the cytosol. Eugenol increased the concentration of potassium ion and cellular materials in the medium. Furthermore, light and scanning electron microscopy observations on hyphae exposed to eugenol revealed considerable morphological alterations in hyphae, such as cytoplasmic coagulation, vacuolation, and hyphal shriveling. Eugenol induced the generation of H2O2 and increased free Ca2+ in the cytoplasm. These results strongly support the idea that the antifungal activity of eugenol is due to membrane binding and permeability alteration, leading to destabilization and disruption of the plasma membrane.