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Abstract(s)
As alergias alimentares são um problema cada vez mais recorrente e a sua prevalência parece estar a aumentar. A alergia alimentar resulta de uma reação imunológica que é desencadeada por um alergénio, nomeadamente proteína, que esteja presente numa bebida, alimento ou aditivo consumido. As alergias, resultantes da resposta imunológica, podem ser mediadas ou não por imunoglobulina E (IgE), sendo que as mediadas por IgE são as mais frequentes. A alergia ao leite, é muito comum em crianças de tenra idade, e os seus principais alergénios são as caseínas e as proteínas do soro. O caseinato de sódio (Cas) resulta da junção das quatro frações de caseínas e é usado numa ampla gama de produtos alimentares, nomeadamente como aditivo alimentar. Com o intuito de diminuir o impacto da alergia ao leite, a indústria tem procurado arranjar soluções para este problema, através do desenvolvimento de técnicas para tentar diminuir a alergenicidade das proteínas do leite, uma vez que não há cura para as alergias, a não ser evitar o consumo do produto alergénico. Os compostos fenólicos têm vindo a requerer elevado interesse, uma vez que a sua interação com as proteínas pode provocar alterações na sua estrutura nativa e assim alterar a sua alergenicidade. Estes compostos podem ser encontrados em frutas, vegetais e sementes. Este trabalho teve como objetivo estudar as interações entre os compostos fenólicos e o caseinato de sódio, e analisar o efeito destas interações na estrutura desta proteína através de técnicas espectroscópicas. Para tal, foram utilizados seis compostos fenólicos, nomeadamente ácido cafeico, ácido gálico, ácido ferúlico, ácido clorogénico, quercetina e ácido tânico. Assim, procedeu-se à fase experimental colocando Cas em contacto com cada um dos compostos fenólicos e analisou-se a ocorrência de alterações na estrutura da proteína. A fim de estudar possíveis alterações na estrutura terciária do Cas promovidas pelos seis compostos fenólicos, foi utilizada a técnica de fluorescência. Os resultados obtidos demonstraram que havia extinção de fluorescência envolvendo maioritariamente um mecanismo estático, o que significa que ocorreu devido à formação de um complexo. O dicroísmo circular foi usado para o estudo das alterações promovidas pela quercetina na estrutura secundária do Cas, tendo sido observado um aumento de hélices-a e uma diminuição de folhas-ß. Foi também realizado um estudo de docking molecular, com a ß-lactoglobulina (ß-LG) e dois compostos fenólicos (quercetina e o ácido tânico) com objetivo de analisar qual o local de ligação destes compostos fenólicos à ß-LG. Esta é uma proteína do soro do leite e uma das principais proteínas alergénicas do leite. A análise por docking molecular demonstrou que o complexo ácido tânico–ß-LG era o mais estável. Este trabalho poderá vir a ser um ponto de partida, para a utilização de compostos fenólicos para a redução da alergenicidade do leite, uma vez que a interação de compostos fenólicos pode promover alterações na estrutura da proteína e assim alterar a sua alergenicidade.
Food allergies are a recurrent problem, and their prevalence appears to be increasing. Food allergy results from an immune reaction that is triggered by an allergen, namely a protein, that is present in a drink, food, or consumer additive. Allergies result from an immune response and those mediated by immunoglobulin E (IgE) are the most frequent. Milk allergy is very common in young children, and its main allergens are caseins and whey proteins. The sodium caseinate (Cas) results from the joining of the four casein fractions and is used in a wide range of food products, namely as a food additive. In order to reduce the impact of milk allergy, the industry has sought to address this problem through the development of techniques to reduce the allergenicity of milk proteins, since there is no cure for allergies and only the eviction of the food is possible. Phenolic compounds are of great interest since their interaction with proteins can cause changes in their native structure and thus alter their allergenicity. These compounds can be found in fruits, vegetables, and seeds. This work aimed to study the interactions between phenolic compounds and Cas and analyze the effect of these interactions on the structure of this protein through spectroscopic techniques. For this, six phenolic compounds were used, namely caffeic acid, gallic acid, ferulic acid, chlorogenic acid, quercetin and tannic acid. Thus, the experiments were carried out by placing Cas with each phenolic compound and analyze the occurrence of alterations in protein structure. In order to study possible changes in the tertiary structure of Cas caused by the six phenolic compounds, a fluorescence technique was used. The results showed that there was fluorescence extinction mostly by static mechanism, which means that the fluorescence extinction occurred due to the formation of a complex. Circular dichroism was used to study the alterations promoted by quercetin in the secondary structure of Cas and demonstrated an increase in a-helix and a decrease in ß-sheets. A molecular docking was carried out with ß-lactoglobulin (ß-LG) and two phenolic compounds (quercetin and tannic acid) in order to analyze the binding site of these phenolic compounds to ß-LG. This is a whey protein and one of the main allergenic milk proteins. Molecular docking analysis showed that the tannic acid – ß-LG complex was the most stable. This work could be a starting point for the use of phenolic compounds to reduce milk allergenicity since the interaction of these compounds can promote changes in the protein structure and thus alter its allergenicity.
Food allergies are a recurrent problem, and their prevalence appears to be increasing. Food allergy results from an immune reaction that is triggered by an allergen, namely a protein, that is present in a drink, food, or consumer additive. Allergies result from an immune response and those mediated by immunoglobulin E (IgE) are the most frequent. Milk allergy is very common in young children, and its main allergens are caseins and whey proteins. The sodium caseinate (Cas) results from the joining of the four casein fractions and is used in a wide range of food products, namely as a food additive. In order to reduce the impact of milk allergy, the industry has sought to address this problem through the development of techniques to reduce the allergenicity of milk proteins, since there is no cure for allergies and only the eviction of the food is possible. Phenolic compounds are of great interest since their interaction with proteins can cause changes in their native structure and thus alter their allergenicity. These compounds can be found in fruits, vegetables, and seeds. This work aimed to study the interactions between phenolic compounds and Cas and analyze the effect of these interactions on the structure of this protein through spectroscopic techniques. For this, six phenolic compounds were used, namely caffeic acid, gallic acid, ferulic acid, chlorogenic acid, quercetin and tannic acid. Thus, the experiments were carried out by placing Cas with each phenolic compound and analyze the occurrence of alterations in protein structure. In order to study possible changes in the tertiary structure of Cas caused by the six phenolic compounds, a fluorescence technique was used. The results showed that there was fluorescence extinction mostly by static mechanism, which means that the fluorescence extinction occurred due to the formation of a complex. Circular dichroism was used to study the alterations promoted by quercetin in the secondary structure of Cas and demonstrated an increase in a-helix and a decrease in ß-sheets. A molecular docking was carried out with ß-lactoglobulin (ß-LG) and two phenolic compounds (quercetin and tannic acid) in order to analyze the binding site of these phenolic compounds to ß-LG. This is a whey protein and one of the main allergenic milk proteins. Molecular docking analysis showed that the tannic acid – ß-LG complex was the most stable. This work could be a starting point for the use of phenolic compounds to reduce milk allergenicity since the interaction of these compounds can promote changes in the protein structure and thus alter its allergenicity.
Description
Keywords
Alergia ao Leite de Vaca Caseinato de Sódio Compostos Fenólicos ß-Lactoglobulina Técnicas Espectroscópicas