Bioatividade de extrato de folhas de Corema album L. em Drosophila melanogaster: um estudo de genotoxicidade e stresse oxidativo
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2015-04-23
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Os radicais que derivam do O2, conceptualmente chamados de espécie reativas de oxigénio (ROS), podem conduzir a um saldo negativo entre oxidantes e antioxidantes, provocando desta forma o stresse oxidativo. O stresse oxidativo pode causar vários danos como a peroxidação lipídica e está associado a processos cancerígenos e genotóxicos. Utilizando Drosophila melanogaster Oregon K como organismo modelo, analisamos o efeito que os extratos foliares de Corema álbum provocam nesse organismo modelo e foram consideros vários aspetos: i) a toxicidade revelada pelos número de mutações e recombinações somáticas; ii) a capacidade antioxidante dos extratos foliares; iii) o nível de danos basais em neuroblastos; iiii) e o papel do stresse oxidativo, avaliando as atividades da Superóxido Dismutase, da Catalase, da Glutationa-S-Transferase e a peroxidação lipídica. Os extratos mostraram-se bastante antioxidantes, em 1 g de folha existem 7,3 mg de equivalentes de GAE ou 36,9 micromoles de equivalentes de Trolox, mas em concentrações mais elevadas não se conseguiu a obtenção de qualquer descendência. Os danos basais detetados sofrem reduções à medida que a concentração do extrato vai diminuindo ocorrendo o inverso nas atividades antioxidante e na peroxidação lipídica. Nos tratamentos onde temos o controlo positivo (paraquato), em conjunto os extratos foliares o comportamento observado continua existir e a ocorrer da mesma forma. No caso do tratamento da concentração mais baixa de extrato observa-se uma resposta antioxidante mais elevada que em qualquer outro tratamento na Superóxido Dismutase e na Glutationa-S-Transferase. Verificou-se nesse mesmo tratamento uma das maiores percentagens de mutação e recombinação somática mas verificou-se também o mais baixo nível de danos basais. Embora os extratos tenham uma grande capacidade antioxidante eles mostram um efeito dual pois para além de promoverem o stresse oxidativo, também causaram toxicidade e genotoxicidade independentemente da relação oxidante/antioxidante.
The radicals deriving from O2, known as reactive oxygen species (ROS), can lead to a negative balance between oxidants and antioxidants, thereby causing oxidative stress. Oxidative stress can cause damages like lipid peroxidation and is also associated with genotoxic and carcinogenic processes. Using Drosophila melanogaster Oregon K as a model organism, we analyzed the effect of Corema album leaf extracts and considered the following aspects: i) the toxicity revealed by the number of somatic mutations and recombinations, ii) the antioxidant capacity of the plant extracts; iii) the basal level of damage in neuroblasts; iiii) and the role of oxidative stress, assessing the activities of Superoxide Dismutase of Catalase, Glutathione-S-transferase and lipid peroxidation. The antioxidant capacity of the extracts was substantial with1 g of leaf extract equivalent to 7.3 mg of GAE or to 36,9 micromoles Trolox equivalents. At higher concentrations it was not able to obtain offsprings. The observed basal damage decreased as the concentration of the extract decreased and the opposite was true in relation to the antioxidant activities and lipid peroxidation. In the treatments where the positive control (paraquat) was applied in addition to the plant extract, the observed behaviour still existed and occurred in the same way. In the case of the treatment with lower concentrations of extract, the antioxidant response is higher than any other treatment in the superoxide dismutase and glutathione-S-transferase. This same treatment caused one of the highest percentages of somatic mutation and recombination but showed the lowestlevel of basdal damage. Although the extracts have a great antioxidant capacity they show a dual effect because they promoted oxidative stress as well as a toxic and genotoxic effect that was independent of the oxidant / antioxidant ratio.
The radicals deriving from O2, known as reactive oxygen species (ROS), can lead to a negative balance between oxidants and antioxidants, thereby causing oxidative stress. Oxidative stress can cause damages like lipid peroxidation and is also associated with genotoxic and carcinogenic processes. Using Drosophila melanogaster Oregon K as a model organism, we analyzed the effect of Corema album leaf extracts and considered the following aspects: i) the toxicity revealed by the number of somatic mutations and recombinations, ii) the antioxidant capacity of the plant extracts; iii) the basal level of damage in neuroblasts; iiii) and the role of oxidative stress, assessing the activities of Superoxide Dismutase of Catalase, Glutathione-S-transferase and lipid peroxidation. The antioxidant capacity of the extracts was substantial with1 g of leaf extract equivalent to 7.3 mg of GAE or to 36,9 micromoles Trolox equivalents. At higher concentrations it was not able to obtain offsprings. The observed basal damage decreased as the concentration of the extract decreased and the opposite was true in relation to the antioxidant activities and lipid peroxidation. In the treatments where the positive control (paraquat) was applied in addition to the plant extract, the observed behaviour still existed and occurred in the same way. In the case of the treatment with lower concentrations of extract, the antioxidant response is higher than any other treatment in the superoxide dismutase and glutathione-S-transferase. This same treatment caused one of the highest percentages of somatic mutation and recombination but showed the lowestlevel of basdal damage. Although the extracts have a great antioxidant capacity they show a dual effect because they promoted oxidative stress as well as a toxic and genotoxic effect that was independent of the oxidant / antioxidant ratio.
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Dissertação de Mestrado em Biologia Clínica e Laboratorial
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Stress oxidativo , Genotoxicidade , Drosophila melanogaster , Antioxidantes , Corema album