Óleos essenciais e extratos vegetais de plantas cultivadas no Brasil: impacto no crescimento de Aspergillus ochraceus e Aspergillus carbonarius

Abstract

Essential oils and plant extracts from aromatic plants are recognized for its antimicrobial properties and effectiveness as food antioxidants. The mycotoxins are toxic metabolites produced by filamentous fungi in feed, being particularly harmful to animals and humans. The mycotoxin occurrence happens after an oxidation process, consequently, the oxidation prevention is a way to avoid mycotoxins production, like ochratoxin A, which is a nephrotoxic toxin, mainly produced by Aspergillus ochraceus, Aspergillus niger and Aspergillus carbonarius in tropical areas. There is evidence that syntetic antioxidants can be prejudicial to animals and humans health. Thus, this study aimed to evaluate the effectiveness of Brazilian plant extracts (essential oils hydrodistillation and hexanic extraction; and vegetal extracts: aqueous and ethanolic) to inhibit the growth of A. ochraceus NRRL 3174 and A. carbonarius RC 2054 (UNRC). A total of 40 plant extracts from ten vegetable species: basil (Ocimum basilicum), cinnamon (Cinnamomum zeylanicum), clove (Eugenia caryophyllata), cumin (Cuminum cyminum), marjoram (Origanum majorana), nutmeg (Myristica fragrans), oregano (Origanum vulgare), rosemary (Rosmarinus officinalis), spearmint (Menta piperita) and sweet fennel (Pimpinella anisum) were screened by diffusion agar test for the best results on mycelial growth inhibition. Oregano essential oils (obtained by hydrodistillation and hexanic extraction), the rosemary essential oil and the clove ethanolic extract were chosen to obtain the growth rate and the lag phase at concentrations of 0, 50, 100, 150, 300 and 600 mg/kg on yeast extract-sucrose agar (YES). Strains were centrally inoculated and the radial growth (mm/day) was daily measured. The growth rate decreased as the essential oil concentration increased in all treatments and fungal strains assayed. The oregano essential oil showed the best results among the other essential oils. Comparing all four treatments, the best result was for clove ethanolic extract and the worst one was for oregano essential oil produced by hexanic extraction. The concentration of 600 mg/kg exerted the best inhibitory effect. These results are interesting related to the prevention of fungi contamination in many foods and they could be used instead of synthetic antifungal products. Future studies should be conducted to determine the ability of these oils and extracts to reduce the ochratoxin A production.