Óleos essenciais de Backhousia citriodora e Lippia origanoides Kunth.: composição química, atividade fungicida e antiocratoxigênica sobre os fungos Aspergillus carbonarius e Aspergillus ochraceus

Abstract

The fruits of coffee plants present favorable organic substances for the development of fungus of the genus Aspergillus, which are responsible for the deterioration of the beverage and occurrence of ochratoxin A. Therefore, studies applying natural products or metabolites of these, like the essential oils for the control of the pathogens and inhibition of the released toxin has intensified. The objective of this study, was to analyze the chemical composition of the essential oils extracted from the leaves of Backhousia citriodora and Lippia origanoides Kunth., as well as to evaluate their fungicidal and ochratoxigenic potential by means of in vitro and in vivo tests on coffee fruits. The essential oils were extracted by hydrodistillation, characterized and quantified by CG / MS and CG / FID. The in vitro antifungal evaluation of the essential oils was carried out on the species A. carbonarius and A. ochraceus; the inhibition of ochratoxin A production, by A. carbonarius and A. ochraceus was evaluated at different concentrations of the oils; the antifungal activity of the essential oils in the coffee fruits, was studied using the plating of the pericarp and the beans; and the inhibition of ochratoxin A synthesis in the coffee bean pericarp and beans was quantified by HPLC. In the essential oil from Backhousia citriodora, the neral and geranial isomers were the principal compounds, whereas the compounds p-cymene, thymol, and carvacrol were the most abundant in the essential oil from L. origanoides Kunth. In vitro antifungal activity against the Aspergillus species studied was observed for both the essential oils in a dose-dependent relationship. These oils inhibited the synthesis of ochratoxin A in the culture medium by both A. carbonarius and A. ochraceus at the concentrations studied. In the evaluation of the antifungal activity of the coffee pericarp, the reduction in the quantity of microorganisms was observed in the presence of the essential oils. In no treatment did the fungi affect the bean. The essential oils had a low antitoxigenic effect on coffee fruits. In the pericarp, the highest concentration of ochratoxin A was verified for both fungi, but it was only quantified in the bean for A. ochraceus. The results obtained were below the limit established by the legislation.