Desenvolvimento de metodologia enzimático-espectrofotométrica baseada em tirosinase para quantificação de catequina e epicatequina em alimentos

• Autor(a) principal: Dias, Tiago
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• dARK ID: ark:/38995/0013000001tp2
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/9910
• topic: Catequina; Epicatequina; Espectrofotometria; Método; Tirosinase; Catechin; Epicatechin; Spectrophotometry; Method; Tyrosinase; CIENCIAS AGRARIAS::CIENCIA E TECNOLOGIA DE ALIMENTOS

Catechin and epicatechin are phenolic compounds of the flavanols class, acting as antioxidants and present in seeds of fruits, like cocoa and apples, in tea leaves and in certain nuts and legumes. The current spectrophotometric methods for catechin and epicatechin analysis are prone to interferences and have low selectivity, requiring to purify and derivatize them before their quantification. Catechin and epicatechin, as o-diphenols, may be derivatized oxidizing them with the tyrosinase enzyme, that catalyzes the conversion of o-diphenols to o-quinones. This work had the purpose of developing an enzymatic spectrophotometric method, to determine total catechin and epicatechin in foods, based on the oxidative derivatization of these substances, by tyrosinase. Seeds of cocoa (Theobroma cacao) were used as the matrix, during the development. The method was evaluated, by analytical validation and was, also, applied to analyze the catechin and epicatechin content in apples with peels (Malus domestica), powdered guarana seeds (Paullinia cupana) and camellia's dried leaves (Camellia sinensis) in sachets, used for the preparation of teas (white, black and green). The method was selective and had high precision, with coefficients of variation below 4%. The accuracy ranged from 84.3% to 90.7%. Total catechin and epicatechin contents, found in the cocoa seeds and guarana powder, approached to the literature data. The method was not adequate to the analysis in apples and in tea leaves, whose total catechin and epicatechin contents were lower than the limit of quantification (1.61 mg g-1 dried basis). The developed method is applicable, with reasonable accuracy, to samples with total catechin and epicatechin contents higher than the limit of quantification. In this condition, selectivity, linearity and precision meet the method's acceptance criteria.