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Abstract(s)
Os radicais livres formam-se naturalmente nos organismos vivos, pois a sua produção/geração está interligada com o processo de produção de energia (respiração), processos inflamatórios (fagocitose), regulação do crescimento celular, sinalização intercelular e síntese de substâncias biológicas relevantes. Estes também podem ser introduzidos por vias exógenas (poluição, radiação, tabaco, alimentação, etc). Os radicais livres têm capacidade de reagir com o material nucleico (ADN e ARN), proteínas e substâncias oxidáveis, causando danos oxidativos responsáveis pelo envelhecimento e originar doenças degenerativas, tais como, o cancro, arteriosclerose, artrite reumatoide, entre outras. De forma a combater os efeitos pejorativos provocados pelos radicais, os organismos vivos desenvolveram complexos sistemas de defesa antioxidante. Estes sistemas são constituídos por antioxidantes endógenos, produzidos pelos seres vivos, tais como enzimas ou por antioxidantes exógenos obtidos por via da alimentação (por exemplo o ácido ascórbico). Neste sentido, um antioxidante tem capacidade de eliminar ou reduzir a propagação da cadeia de geração de radicais livres.
Neste trabalho foi desenvolvido um biossensor enzimático para a quantificação da capacidade antioxidante total de matrizes alimentares. A construção deste biossensor consistiu na eletroimobilização da adenina no elétrodo de pasta de carbono (EPC) ou na adsorção física da dA20 na superfície do EPC. O dano oxidativo foi induzido pelo radical hidroxilo gerado pela reação de Fenton. Nesta dissertação, foi estudada a capacidade de alguns antioxidantes em eliminar o efeito pejorativo dos radicais livres e combater a integridade das bases de adenina ou do dA20.Os antioxidantes estudados foram o ácido ascórbico e alguns ácidos fenólicos como o ácido hidroxibenzoico (ácido gálico) e ácidos hidroxicinâmicos (ácido cafeico e ácido cumárico). Estes antioxidantes têm a capacidade de neutralizar o radical hidroxilo e proteger a adenina/dA20 imobilizado na superfície do EPC. O comportamento da Lacase foi estudado na presença do ácido gálico e do ácido ascórbico. Os estudos eletroquímicos foram realizados através da voltametria de onda quadrada (VOQ), sendo que a interação entre a adenina/ou o dA20 imobilizada na superfície do EPC e os radicais livres na ausência e presença de antioxidantes foi avaliada por meio de mudanças no pico anódico produzido pela oxidação da adenina /dA20.
Os resultados demonstraram que estes biossensores permitem a avaliação da capacidade antioxidante total em águas aromatizadas.
Free radicals are formed naturally in living organisms , since the production/ generation is interconnected with the process of energy production (respiration), inflammatory response (phagocytosis), regulation of cell growth, intercellular signaling and synthesis of relevant biological substances. Radicals may also be introduced by exogenous pathways (pollution, radiation, tobacco, diet, etc.). The free radicals are capable of reacting with nucleic material (DNA and RNA), proteins and oxidizable substances causing oxidative damage responsible for aging and lead to degenerative diseases such as cancer, atherosclerosis, and rheumatoid arthritis, among others. In order to combat the derogatory effects caused by radicals, living organisms have developed complex antioxidant defense systems. These systems are composed by endogenous antioxidants, produced by living organisms, such as enzymes or exogenous antioxidants obtained by means of diet (for example ascorbic acid). In this context, an antioxidant is capable to eliminate or reduce the spread of the generation chain radicals. In this thesis we developed a biosensor to quantify enzymatic antioxidant capacity of food matrices. The construction of the biosensor consists on the adenine eletroimobilization in the carbon paste electrode (CPE) or physical adsorption of dA20 on the CPE surface. Oxidative damage was induced by hydroxyl radical generated by the Fenton reaction. The ability of certain antioxidants to eliminate the derogatory effect of free radicals and combat the integrity of the adenine bases or dA20 was studied. Ascorbic acid and some phenolic acids such as hydroxybenzoic acid (gallic acid) and hydroxycinnamic acids (caffeic acid, coumaric) were used as antioxidants. These have the capability to neutralize the hydroxyl and protect adenine/ dA20 on the EPC surface.The behavior of laccase was studied in the presence of gallic acid and ascorbic acid. Electrochemical studies were performed by square wave voltammetry (swv), and interaction between adenine/dA20 and free radicals in the absence and presence of antioxidants were evaluated by changes in the anodic peak produced by the oxidation of adenine/dA20. The results demonstrated that these biosensors allow the assessment of total antioxidant capacity in flavored waters.
Free radicals are formed naturally in living organisms , since the production/ generation is interconnected with the process of energy production (respiration), inflammatory response (phagocytosis), regulation of cell growth, intercellular signaling and synthesis of relevant biological substances. Radicals may also be introduced by exogenous pathways (pollution, radiation, tobacco, diet, etc.). The free radicals are capable of reacting with nucleic material (DNA and RNA), proteins and oxidizable substances causing oxidative damage responsible for aging and lead to degenerative diseases such as cancer, atherosclerosis, and rheumatoid arthritis, among others. In order to combat the derogatory effects caused by radicals, living organisms have developed complex antioxidant defense systems. These systems are composed by endogenous antioxidants, produced by living organisms, such as enzymes or exogenous antioxidants obtained by means of diet (for example ascorbic acid). In this context, an antioxidant is capable to eliminate or reduce the spread of the generation chain radicals. In this thesis we developed a biosensor to quantify enzymatic antioxidant capacity of food matrices. The construction of the biosensor consists on the adenine eletroimobilization in the carbon paste electrode (CPE) or physical adsorption of dA20 on the CPE surface. Oxidative damage was induced by hydroxyl radical generated by the Fenton reaction. The ability of certain antioxidants to eliminate the derogatory effect of free radicals and combat the integrity of the adenine bases or dA20 was studied. Ascorbic acid and some phenolic acids such as hydroxybenzoic acid (gallic acid) and hydroxycinnamic acids (caffeic acid, coumaric) were used as antioxidants. These have the capability to neutralize the hydroxyl and protect adenine/ dA20 on the EPC surface.The behavior of laccase was studied in the presence of gallic acid and ascorbic acid. Electrochemical studies were performed by square wave voltammetry (swv), and interaction between adenine/dA20 and free radicals in the absence and presence of antioxidants were evaluated by changes in the anodic peak produced by the oxidation of adenine/dA20. The results demonstrated that these biosensors allow the assessment of total antioxidant capacity in flavored waters.
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Keywords
Radicais livres Biossensor enzimático ADN Antioxidantes Eletroquímica Elétrodo de pasta de carbono Free radicals Enzymatic biosensor DNA Antioxidants Electrochemical Carbon paste electrode