Estudo da estabilidade e do efeito fungitóxico do óleo essencial de capim-limão (Cymbopogon citratus (D.C.) Stapf)

Abstract

Essential oils have been increasingly employed in the foods (aromas and spices for food and beverages) and cosmetics (perfumes and hygiene products). Most of these compounds have important biological action, making of them the objective of research in the agrochemical industry, in the search for natural fungicides, bactericides and insecticides. Lemongrass (Cymbopogon citratus), is an aromatic plant raised for the commercial production of essential oil. The present research was designed to evaluate the chemical composition, the stability to light and temperature, and the antifungal activity of this oil on the plant pathogens Fusarium oxysporum, Colletotrichum gloeosporioides and Rhizoctonia solani. The identification of the chemical compounds of the essential oil was performed on a gas chromatograph coupled to a mass spectrometer. To evaluate the stability of the oil, it was submitted to the presence and absence of light and to different temperatures. The yields of the major compounds, citral and myrcene, were evaluated every fifteen days in a gas chromatograph with a FID detector using analytical curves constructed with standard solutions. The in vitro bioassay method was used to determine the fungitoxic activity, in which the essential oil, the major compounds and the commercial fungicide (Tebuconazole) were applied in several concentrations to the plant pathogens. The major compounds of the essential oil of lemongrass, citral and myrcene, were degraded with time in both the presence and absence of light, but temperature only influenced the degradation of myrcene. The essential oil completely inhibited the mycelial growth of the plant pathogens at the concentration of 250 ppm for Rhizoctonia solani, and at 500 ppm for Fusarium oxysporum and Colletotrichum gloeosporioides, suggesting that this activity can be a result of the presence of citral.