GELEYS BRAIDO AVANÇO
Título da Dissertação: COMPOSIÇÃO E EFEITO ANTIOXIDANTE DO ÓLEO ESSENCIAL DE Curcuma longa L. E AÇÃO SOBRE O
DESENVOLVIMENTO E PRODUÇÃO DE FUMONISINAS POR Fusarium verticillioides
Orientador: Prof. Dr. Miguel Machinski Junior
Data da Defesa: 27/03/2014
RESUMO GERAL
INTRODUCTION: The essential oil of turmeric (Curcuma longa) has shown toxicity against fungi involved in food spoilage. Among these, Fusarium verticillioides, cosmopolitan fungus of great economic importance in agriculture because it infects and causes damage to various crops. F. verticillioides is fumonisin producer mainly fumonisin B1 (FB1), responsible for causing diseases in animals such as equine leukoencephalomalacia, and possibly carcinogenic in humans (class 2B), according to the International Agency for Research on Cancer - IARC. Studies in humans have shown a high incidence of esophageal cancer and association with liver cancer related to consumption of contaminated food with high levels of FB1. The use of synthetic fungicides in the control of plant pathogens has shown problems in relation to the development of microbial resistance as well as undesirable effects to consum ers, increasing attention to the use of antimicrobial drugs of natural origin. Essential oils from plants like tumeric, can become an alternative to synthetic chemicals used to combat these fungi, reducing the environmental impact and risks to human and animal health.
OBJECTIVES: This study aimed to evaluate the chemical composition and antioxidant activity of essential oil from fresh rhizomes of Curcuma longa L. and its antifungal activity and antimycotoxigenic in Fusarium verticillioides ( Sacc. ) Niremberg. MATERIAL AND METHODS: The essential oil of C. longa was obtained by hydrodistillation by Clevenger apparatus. The identification of the composition of the oil was performed by gas chromatography coupled to mass spectrometry (GC -MS) and nuclear magnetic resonance (NMR). The turmeric oil was evaluated the antioxidant activity for the methods of DPPH (2,2-diphenyl-1-picryl-hydrazyl) , ABTS (2,2'- azinobis-3-ethylbenzthiazoline-6-sulfonic acid), power reducer and chelating effect of the ferrous ion. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of the essential oil of turmeric were determined according to Norm M38 from Reference Method for Broth Dilution Tests for Determining the Sensitivity to Therapy Antifungal Filamentous Fungi. The action of the essential oil on the development and morphology of F. verticillioides was observed by cultivation in medium rich in sugars and amino acids, ergosterol determination, optical microscopy and scanning electron microscopy. Antimycotoxigenic activity of the turmeric essential oil in F. verticillioides was evaluated by determination of FB1 and FB2 by high liquid chromatography coupled to mass spectrometry (LC-MS/MS). Results were analyzed statistically using GraphPad Prism, version 5 program.
RESULTS AND DISCUSSION: The main volatile compounds identified in the essential oil of C. longa were α - turmerona (42.6 %), β - turmerona (16.0%) and ar - turmerona (12.9%). The oil showed good antioxidant activity for ABTS radical and the concentration of essential oil needed to inhibit 50% of the radical (IC50) of 0.54 mg/mL activity. In relation to reducing power oil also showed activity, being lowest for the DPPH radical (IC50 = 10.03 mg/mL) with no chelating activity for ferrous ion. The development of F. verticillioides was inhibited in the presence of turmeric oil compared to fungal control, with a reduction from 56.0 to 79.3 % in its growth, with concentrations ranging between 17.9 and 294.9 μg/mL respectively. The oil was able to alter the production of conidia and hyphae. The ergosterol production o decreased significantly (p<0.05) in the groups treated with the essential oil in relation to the control, demonstrating the oil activity in fungal biomass. FB1 and FB2 production was inhibited significantly (p<0.05) in groups treated with essential oil. Therefore, there is a direct relationship between the inhibitory effect caused by the essential oil of turmeric in the development and fumonisins biosynthesis.
CONCLUSIONS: C. longa essential oil showed antifungal activity and antimycotoxigenic in the concentrations evaluated, and good antioxidant activity compared to the tested radicals. The major compounds determined in this study were similar to those found by other authors, when they analyzed the chemical composition of essential oil of fresh turmeric rhizomes. Therefore, the essential oil of turmeric grown in Brazil may be an alternative to the use of synthetic fungicides to control toxigenic fungi such as F. verticillioides.
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