Avalia??o das atividades antif?ngicas de subst?ncias sint?ticas frente a fungos micotoxig?nicos de interesse agropecu?rio

• Autor(a) principal: Paiva, Rojane de Oliveira
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFRRJ
• Texto Completo: https://tede.ufrrj.br/jspui/handle/jspui/3178
• topic: Antif?ngicos; Aspergillus; Fusarium,; Penicillium; Micotoxicologia; Antifungal; Mycotoxicology; Medicina Veterin?ria

Fungi mycotoxigenic cause economic losses in the agricultural sector. The aim of this study was to evaluate the antifungal activity of synthetic substances against fungi mycotoxigenic of agricultural interest in Brazil and Argentina. They were measured the minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) of the classes of substances semicarbazones, monosubstituted thiosemicarbazones, disubstituted thiosemicarbazones, Schiff bases and the class mesoionic compounds against Aspergillus flavus, Aspergillus nomius, Aspergillus ochraceus, Aspergillus parasiticus, Fusarium verticillioides and Penicillium citrinum. Substances with antifungal activity were selected to study the possible routes of action mechanism. The influence of the substances on the ergosterol content, in the fungal development of the vegetative system, and chelating effect of Fe2+ and cytotoxicity were evaluated. The MIC and MFC were determined for 9 semicarbazones (SM 1-9), and SM-1 and SM-4 had fungistatic effect against A. flavus and F. verticillioides. The 8 monosubstituted thiosemicarbazones (TS 1-8) were evaluated, and 7 substances have fungistatic effect, TS-6 had fungistatic effect against all species of the genus Aspergillus and fungicidal showed effect against F. verticillioides. A. parasiticus was more sensitive to the action of these substances. In this class, 36 disubstituted thiosemicarbazones were evaluated, (TS 1-36) whence 13 substances have antimicrobial activity against A. parasiticus and Candida albicans yeast. Sevemn substances from Schiff base class derived from aldehydes and aminopyridine were evaluated, all of which had fungistatic effect, but (BS-7) presented fungicidal action. The substances showed antibacterial activity. Antifungal activities of 16 mesoionic compounds (MI 1-16) were investigated. Most of mesoionic compounds showed antifungal activity against all fungi evaluated. F. verticillioides had higher sensitivity with MIC values varied from 7.8 to 125 ?g/mL. Phenyl-substituted with groups of electron donors (MI-11 and 16) was the series of mesoionic compounds with the highest antifungal effect; followed by esteryl-substituted with ring directly linked to the heterocyclic ring-carbon (MI- 1-3 and 5). MI-11 and 3 derivatives have the most prominent MIC values of 7.8 and 15.6 ?g/mL, respectively. A. flavus, A. nomius and A. parasiticus had MICs = 250 ?g / mL for MI- 5 and MIC = 31.2 ?g / mL and MFC = 125 ?g / mL for F. verticillioides. The substances thiosemicarbazones (TS-3 and TS-6) and mesoionic compounds (MI-2, MI-11 e MI-16) decreased ergosterol content, evaluated by high performance thin layer chromatography (HPTLC) in A. parasiticus and F. verticillioides. The thiosemicarbazones TS-3 and TS-6 altered the development of the vegetative system of A. parasiticus.The quelant effect determined by UV-Visible spectroscopy for TS-6 against Fe2+ ions was confirmed. Finally, the cytotoxicity evaluation of substance from the monosubstituted thiosemicarbazone classes (TS-6) was performed with Vero cells and maximum non-cytotoxic concentration (MNCC) was calculated (MNCC = 75 ?g/ml). In addition, 50% cytotoxic concentration (CC50) was also determined (CC50 = 136 ?g/ml) by neutral-red uptake and (CC50 = 344 ?g/ml) by MTT metabolic reduction. Results suggest antifungal activities against mycotoxigenic fungi of the substances from all the researched classes.