Evaluation of antifungal activity of the essential oils from Baccharis dracunculifolia and Lippia sidoides on fungal growth and aflatoxin B1 production by Aspergillus flavus

Abstract

Alternatives to synthetic pesticides used in agriculture, including in grains storage, have been thoroughly studied worldwide. Among several possibilities of natural compound sources, essential oils are an alternative with a rich variety of bioactive compounds. The essential oils to be studied in this research will be extracted from leaves of Baccharis dracunculifolia and Lippia sidoides, which are species abundantly found in some Brazilian regions. Antifungal activity will be assessed using the fungus Aspergillus flavus, which is responsible for many losses in grain storage, as result of its growth and aflatoxin production. The objective of this study will be to evaluate the capacity that in vitro treatment with the essential oils Baccharis dracunculifolia and Lippia sidoides, separately and in combination, has on fungal growth and aflatoxin B1 production, and, at a later stage, to evaluate the best treatment in vivo, using as substrate irradiated and natural (with natural microflora) maize grains, with added inoculum. The evaluation of in vitro fungal growth will be carried out visually when the method M38A of CLSI, formerly NCCLS (NCCLS, 2002) is used, and by radial growth measurement of colonies when the method of ALVAREZ-CASTELLANOS et al (2001) is used. In the in vivo evaluation, the intensity of microflora will be evaluated by mould and yeast count. The effect of the treatments on aflatoxin production will be evaluated by High Performance Liquid Chromatography (HPLC).The identification of the chemical composition of the essential oils will be carried out by gas chromatography. The statistical analysis will be carried out by analysis of variance and Tukey test for comparison of means, using Statistical Analysis System (SAS, 2003). (AU)