Inhibitory effect of essential oils on growth and on aflatoxins production byAspergillus parasiticus

Abstract

The aim of this work was to assess the inhibitory effect of essential oils on the growth and aflatoxin production ofAspergillus parasiticus, as well as to correlate it with the chemical composition of the essential oils. Essential oils from six aromatic species (Cymbopogon citratus,Eucalyptus globulus,Origanum vulgare,Ruta graveolens,Salvia officinalis, Satureja montana) were characterised by gas chromatography and tested for their inhibitory effect againstA. parasiticus strain MUM 92.02. Furthermore, thein vitro inhibitory effects of these essential oils on the production of aflatoxins were evaluated by HPLC. Results showed that all essential oils retarded the time for visible growth. Growth rate was affected differently depending on the essential oil.S. montana essential oil prevented growth in all cases. The essential oil ofR. graveolens inhibited most of the aflatoxin production even though growth inhibition was low, while withC. citratus essential oil trace levels of aflatoxins were detected. Essential oils containing carvacrol and/or thymol (S. montana andO. vulgare) have the highest activity against fungal growth, while an essential oil (R. graveolens) containing 2-undecanone and 8-phenyl-2-octanone inhibited the synthesis of aflatoxins. Although the main component of this essential oil was 2-undecanone (91%), when pure 2-undecanone was tested, it did not inhibit aflatoxin production. Inhibition activity is probably due to the recently identified minor compound or to a synergistic effect. Essential oils seem to be a good alternative to fungicides not only because of environmental issues but also because they do not seem to enhance mycotoxin production as it has been reported for some fungicides.