Estudo da estrutura e da atividade biológica do pigmento melanina produzido pelo fungo Aspergillus nidulans

Abstract

Do fungo Aspergillus nidulans foi isolado um mutante que apresenta producao aumentada do pigmento melanina. Este pigmento, formado pela polimerizacao oxidativa de compostos fenolicos e/ou indolicos, pode estar presente na parede celular ou no meio de cultura. Embora nao seja essencial para o crescimento dos fungos, a melanizacao parece aumentar a capacidade de sobrevivencia das especies em condicoes desfavoraveis, fornecendo protecao contra radiacao UV, altas temperaturas, enzimas hidroliticas, metais pesados e agentes oxidantes. A obtencao deste pigmento, na forma pura, tem despertado interesse biotecnologico devido a sua utilizacao em formulacoes cosmeticas, principalmente pela sua propriedade fotoprotetora e antioxidante. Tendo em vista o potencial farmacologico do pigmento melanina, este trabalho tem como objetivos fazer a caracterizacao estrutural e funcional do pigmento extraido do fungo A. nidulans. Os resultados de espectrometria de massas indicam que a estrutura da melanina do fungo A. nidulans e composta de duas grandes unidades, representadas pelos fragmentos de massas moleculares igual a 573 e 550, com grupamentos diidroxindol e aneis pirrolicos substituidos. Os ensaios de citotoxicidade mostram que a melanina extraida do fungo A. nidulans nao causa danos significativos aos componentes celulares, tanto antes como pos metabolizacao. Os ensaios de mutagenicidade sugerem que a melanina nao apresenta propriedades mutagenicas para as linhagens TA 97a, TA 98, TA 100 e TA 102 de Salmonella thyphimurium. No teste antimicrobiano, observase que a melanina do fungo nao apresenta potencial como antibacteriano frente a Staphylococcus aureus, Escherichia coli e Enterococcus faecalis, quando comparadas com as substancias de referencia, ampicilina e cloranfenicol. Quanto...

A mutant that presents increased production of the melanin pigment was isolated from the Aspergillus nidulans fungus. This pigment, formed by the oxidative polymerization of phenolic and/or indolic compounds, can be present in the cellular wall or culture medium. Although it is not essential for the fungal growth, melanization seems to increase the survival capacity of the species in unfavorable conditions, supplying protections against UV radiation, high temperatures, hydrolytic enzymes, heavy metals and oxidants agents. The attainment of this pigment, in its pure form, has taken biotechnological interest due to its use in cosmetic formulations, mainly for its photoprotector and antioxidant property .Considering the pharmacological potential of the melanin pigment, this study aims to make the structural and functional characterization of the pigment extracted from A. nidulans fungus. The results of mass spectrometry indicate that the melanin structure of the A. nidulans fungus is composed of two large units, represented by the fragments of molecular mass equal to 573 and 550, with dihydroxyindole groups and substituted pyrrolic rings. The cytotoxicity assays have shown that the melanin extracted from the A. nidulans fungus does not cause significant damages to the cellular components, before and after metabolization. The mutagenicity assays suggest that the melanin does not present mutagenic properties for the strains TA 97a, TA 98, TA 100 and TA 102 of Salmonella thyphimurium. In the antimicrobial test, it is observed that the fungal melanin does not present antibacterial potential facing Staphylococcus aureus, Enterococcus faecalis and Escherichia coli, when compared to the reference substances, ampicilin and cloranphenicol. Regarding the immunomodulatory activity, it was verified that the melanin does not stimulate NO release... (Complete abstract click electronic access below)