RESUMO
O objetivo deste estudo foi avaliar os efeitos do timol e carvacrol contra Aspergillus flavus e a produção de aflatoxinas. Foram determinadas a concentração inibitória mínima (CIM), o espectro fungitóxico e a atividade inibidora de micotoxinas pelo timol e carvacrol. Os resultados mostraram que timol e carvacrol exibiram ação fungicida de acordo com a CIM de 2500 e 30 µg mL-1, respectivamente. Tanto o timol quanto o carvacrol inibiram significativamente o crescimento de A. flavus (p<0,05) a partir de 600 e 15 µg mL-1, respectivamente. A biomassa fúngica, estimada pela determinação da concentração de ergosterol, foi significativamente reduzida (p <0,05) em 2500 µg mL-1 de timol e 250 µg mL-1 de carvacrol. O timol e o carvacrol exibiram efeitos antiaflatoxigênicos em 600 e 125 µg mL-1, respectivamente. O timol e o carvacrol exibiram atividade antifúngica, mas não exibiram alta atividade antiaflatoxigênica. Carvacrol e timol podem ser considerados como potentes compostos naturais antifúngicos contra A. flavus.
The aim of this study was to evaluate the effects of thymol and carvacrol upon production of aflatoxins by Aspergillus flavus and upon its growth. Minimal inhibitory concentration (MIC), fungitoxic spectrum and mycotoxin inhibition were assessed. Results showed thymol and carvacrol exhibited fungicidal action, as determined by MIC values of 2500 and 30 µg mL-1, respectively. Both thymol and carvacrol significantly inhibited growth of A. flavus (p<0.05) at concentrations of 600 and 15 µg mL-1, respectively. Fungal biomass, as estimated by determination of ergosterol concentration, was significantly reduced (p<0.05) at thymol concentrations of 2500 µg mL-1 and at carvacrol concentrations of 250 µg mL-1. Thymol and carvacrol exhibited antiaflatoxigenic effects at concentrations of 600 and 125 µg mL-1, respectively. While both thymol and carvacrol showed possessing antifungal activities, neither were highly antiaflatoxigenic. Carvacrol and thymol might be considered for use as potential antifungal natural compounds against A. flavus.
RESUMO
The increased risk to health by diverse pathologies, such as cancer, liver diseases, and endocrine alterations, caused by chemical residues in food, has led to the search for sustainable agricultural management alternatives, such as the use of essential oils for the development of natural and eco-friendly fungicides. The aim of this study was to evaluate the antifungal and antiaflatoxigenic activity of Rosmarinus officinalis L. essential oil (REO) against Aspergillus flavus Link. REO was obtained by hydrodistillation and its major components were identified as 1,8-cineole (eucalyptol, 52.2%), camphor (15.2%) and α-pinene (12.4%) by GC/MS and NMR. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were both 500 µg/mL. REO reduced the mycelial growth of A. flavus at a concentration of 250 µg/mL (15.3%). The results obtained from scanning electron microscopy (SEM) demonstrated a reduction in the size of conidiophores and in the thickness of hyphae in A. flavus caused by treatment with REO (250 µg/mL). The production of ergosterol and the biomass of mycelium were both reduced as the REO treatment concentration increased. The production of aflatoxins B1 and B2 was inhibited after treatment with 250 µg/mL REO, a concentration below the MIC/MFC, indicating that the antiaflatoxigenic effect of REO is independent of its antifungal effect and is likely due to its direct action upon toxin biosynthesis. The data demonstrated that REO may be used as an alternative to synthetic fungicides.
