Composição química e atividade antifúngica de óleos essenciais de cinco espécies de Eucalyptus sobre Hemileia vastatrix e Penicillium citrinum

Abstract

Plants have been used by humans since ancient times as spices or as a quick, effective and inexpensive way to combat diseases and microorganisms. Essential oils are formed by the secondary metabolism of plants and can be extracted from all the organs of the plant. They are complex mixtures of several constituents that can present several activities, including antifungal activity. The Coffea sp. coffee tree is a shrub of the Rubiaceae family of the genus Coffea L. The seed contained in its fruit is used to make coffee, one of the most widely consumed beverages in the world, directly influencing the Brazilian economy because this country is the largest producer of coffee. Two fungi that cause losses in the production of these grains are Hemileia vastatrix and Penicillium citrinum. The former is known as the coffee tree rust, and it attacks the crop, causing a peeling of the bushes and directly affecting the next fruit production. The Penicillium citrinum fungus attacks the coffee beans during the transportation and storage period, changing the visual, qualitative aspect and the quantitative analysis of the grains. The objective of this work was to characterize the in vitro and in vivo antifungal activity of the essential oils of Eucalyptus torelliana, Eucalyptus citriodora, Eucalyptus camaldulensis, Eucalyptus grandis and Eucalyptus microcorys against Hemileia vastatrix and Penicillium citrinum. The essential oils were extracted by the hydrodistillation technique, using the modified Clevenger apparatus; the chemical characterization was performed by GC/MS and GC/FID; the in vitro antifungal activity of the essential oils against Hemileia vastatrix was studied by evaluating the percentage of germination; The in vitro antifungal activity of the essential oils against Penicillium citrinum was studied by evaluating the mycelial growth. In vivo antifungal activity was performed using the Hemileia vastatrix fungus, and the curative and preventive effect of the essential oils were evaluated. The principal constituents of the essential oils of E. citriodora (citronellal, citronellol and isopulegol); E. torreliana (α-pinene, 1,8-cineol and β-pinene); E. camaldulensis (1,8-cineole, α-terpineol and α-pinene); E. grandis (1,8-cineole, α-pinene and α-terpineol) and E. microcorys (1,8-cineole, α-pinene and transpinocarveol) were determined. In vitro and in vivo antifungal activity against the two fungi under study was observed for all the essential oils, except the essential oil from E. microcorys, which did not present antifungal activity in vivo, but acted as a preventive agent against the fungus Hemileia vastatrix.