Possíveis mecanismos de atividade antifúngica de óleos essenciais contra fungos patogênicos

Abstract

A microbiological screening tested ten essential oils and three phytochemicals in solid discs with a sterile medium to evaluate the susceptibility of diferent fungal strains. Oils from C. zeylanicum, O. majorana, O. vulgare were chosen due to their efficient antifungical activity against twenty-one strains analyzed. The tests that determine CIM and CFM have proven through essential oils from C. zeylanicum and O. vulgare were able of causing death on yeast and filamentous strains. The analyze about of the inhibition mycelial growth potential by kinetics of microbial death indicates which essential oils from cinnamon and oregano obtained a important antifungal activity compared with essential oil of marjoram. The oils were able to interfere accentually in the logarithmic phase of yeast during twenty-four hours exposure. This antifungal activity was compared with fungistatic and fungicidal effect of ketoconazole. In regard to count of yeasts, there was not a significant difference (p> 0.05) between to essential oils and the standard antifungal, ketoconazol. The fumigant effect of the essential oils examined in an optical microscope indicates that the possible mechanism of action is an interference with cell wall formation. In agreement with what research suggests, this study tested the effect of sorbitol, an osmotic protector which is a complement, this way, microscopic changes, such as: decreased percentage of cytoplasm, loss of pigmentation, deficient development of hyphae and empty hyphae were observed. This present study also analyzed the essential oils tested against resistant strains caused in part by the presence of efflux proteins on the membrane of some them.