Chemical characterization and determination of in vivo and in vitro antifungal activity of essential oils from four Eucalyptus species against the Hemileia vastatrix Berk and Br fungus, the agent of coffee leaf rust

Abstract

Essential oils, also known as volatile oils, are substances produced through the secondary metabolism of plants. In this study, we determined the chemical composition and the in vitro and in vivo antifungal activity of the essential oils from four species of Eucalyptus, Eucalyptus citriodora, Eucalyptus camaldulensis, Eucalyptus grandis and Eucalyptus microcorys, against the Hemileia vastatrix fungus. The essential oils from these four species of Eucalyptus were extracted from their leaves by the hydrodistillation technique using a modified Clevenger apparatus. The chemical characterization was performed by gas chromatography coupled with a mass spectrometer detector and by gas chromatography using a flame ionization detector. The antifungal activities of the essential oils against H. vastatrix were studied by evaluating the percentage of spore germination using the microdilution test for in vitro assays. The curative and preventive effects were evaluated in in vivo tests. The principal constituents of the essential oil from E. citriodora were citronellal, citronellol and isopulegol, while E. camaldulensis produced 1,8-cineole, α-terpineol and α-pinene. 1,8-cineole, α-pinene and α-terpineol were obtained from E. grandis and 1,8-cineole, α-pinene and trans-pinocarveol were the principal components in the essential oil of E. microcorys. In vitro and in vivo antifungal activities against the fungus under study were observed for most of the essential oils, except the essential oil from E. microcorys, for which no preventive antifungal activity was observed. Only the curing of infection by the H. vastatrix fungus was observed with this oil.