ABSTRACT
The morphological features of a Penicillium, isolated from Brazilian cerrado soil, were characterized and showed to be distinctly different from all well-defined Penicillium species. Chemical and biological investigation on the ethyl acetate extract of this Penicillium isolate resulted in the isolation of three new naphthalenoids: a major metabolite, methyl 6-acetyl-4-methoxy-5,7,8-trihydroxynaphthalene-2-carboxylate and two minor ones, methyl 6-acetyl-4-methoxy-7,8-dihydroxynaphthalene-2-carboxylate and methyl 6-acetyl-4-methoxy-5,8-dihydroxynaphthalene-2-carboxylate. Their structures were determined based on their mono and bidimensional nuclear magnetic resonance data. Acetyl, allyl and methoxyl derivatives of the major metabolite were prepared in order to establish structure-activity relation. Antimicrobial activity of the major natural product and its semi-synthetic derivatives was screened by macro dilution methodology and the corresponding minimum inhibitory concentrations were determined. Natural secondary metabolite methyl 6-acetyl-4-methoxy-5,7,8-trihydroxynaphthalene-2-carboxylate, isolated in a very high yield (0.3175 mg.L-1) showed to be the most active compound, possessing expressive activity against Candida albicans (minimum inhibitory concentration (MIC) 32 ug/mL), Listeria monocitogenes and Bacillus cereus (MIC 64 µg/mL for both).
Subject(s)
Animals , Fungi/isolation & purification , Penicillium/isolation & purification , Penicillium/classification , Penicillium/metabolism , Brazil , Magnetic Resonance Spectroscopy/methods , Methylation , Disk Diffusion Antimicrobial Tests/methodsABSTRACT
As a part of a research program that aims to identify antibacterial and antifungal substances from fungus specimen of Brazilian's cerrado soil samples, Penicillium sclerotiorum was identified as a source of secondary metabolites possessing antibiotic activities. This microorganism was cultured in a liquid medium rich in glucose for fifteen days. The resulting ethyl acetate extract was chemically fractionated leading to the isolation of three metabolites pencolide, sclerotiorin and isochromophilone VI. The antimicrobial disc assay activity of these substances towards Candida albicans, Streptomyces pyogenes, Staphylococcus aureus, Salmonella typhimurium and Escherichia coli was performed. Minimum inhibitory concentration (MIC) of the compounds was determined. All compounds showed distinguished antimicrobial activities.
Como parte de um programa de pesquisa visando a identificação de substâncias antibacterianas e antifúngicas a partir de espécies fúngicas isoladas de solo do cerrado, foi estudado o fungo Penicillium sclerotiorum van Beyma. Este microrganismo foi cultivado em meio líquido rico em glicose e, após extração com acetato de etila, este foi quimicamente fracionado levando ao isolamento de três metabólitos pencolídeo, esclerotiorina e isocromofilona VI. A atividade destas três substâncias, por meio de teste de difusão em discos, contra Candida albicans, Streptomyces pyogenes, Staphylococcus aureus, Salmonella typhimurium e Escherichia coli foi avaliada. A concentração inibitória mínina das substâncias ativas foi determinada.