Determinação eletroanalítica do flavonoide glicosilado canferitrina em infusos de Bauhinia forficata utilizando eletrodos de diamante
Data
2021-12-02
Autores
Simião, Carolina Godinho 
Orientadores
Oliveira, Lucia Codognoto de
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Neste trabalho foi estudado o comportamento eletroquímico do flavonoide glicosilado canferitrina e desenvolvida uma metodologia eletroanalítica para sua determinação em infusos de Bauhinia forficata, utilizando eletrodo de diamante dopado com boro (BDD). O estudo do comportamento eletroquímico do flavonoide em voltametria cíclica, apresentou dois picos de oxidação, um em 0,80 V vs Ag/AgCl, e outro em torno de 1,0 V vs Ag/AgCl, com característica de um processo irreversível. O estudo de influência do pH do meio mostrou ser o pH 7,0 o mais adequado para o trabalho, uma vez que apresentou maior intensidade de corrente de pico. A análise da variação da velocidade de varredura mostrou que a corrente de pico varia linearmente com a raiz quadrada da velocidade de varredura, indicando que o processo é controlado por difusão (pico 1 em 0,80 V). Os estudos com a voltametria de onda quadrada (técnica selecionada para o desenvolvimento da metodologia) tiveram como parâmetros otimizados f = 100 s-1, a=90 mV e ΔEs = 8 mV. Após a otimização dos parâmetros, foi construída a curva analítica para a canferitrina no intervalo de concentração de 3,4 x10-6 mol L-1 a 5,8 x10-5 mol L-1 com linearidade de 0,99, os limites de detecção e quantificação foram de 3,6 x10-6 mol L-1 e 1,2x10-5 mol L-1, respectivamente. Em paralelo foram realizados testes com eletrodo de grafite de lapiseira, onde o perfil voltamétrico da canferitrina foi similar ao observado com o eletrodo de BDD. Os limites de detecção e quantificação obtidos foram de 1,1x10-5 e 3,6x10-5, respectivamente. No entanto, o eletrodo de BDD foi o selecionado para a quantificação da canferitrina em Bauhinia forficata, pois apresentou melhor repetibilidade dos resultados. Foi encontrada uma concentração de 20 mg L-1 de canferitrina em 2 g de amostra de folhas secas de pata-de-vaca. Por fim foi realizado testes com outros dois flavonoides (crisina e apeginina) para comparar e propor um mecanismo de oxidação para a canferitrina. Os estudos eletroquímicos permitiram a determinação da canferitrina em infusos de Bauhinia forficata e também propor um mecanismo de oxidação para este composto sobre o eletrodo de BDD.
In this work, the electrochemical behavior of the glycosylated flavonoid kaempferitrin was studied and an electroanalytical methodology was developed for its determination in infusions of Bauhinia forficata, using a boron-doped diamond electrode (BDD). The study of the flavonoid's electrochemical behavior in cyclic voltammetry showed two oxidation peaks, one at 0.80 V vs Ag/AgCl, and another around 1.0 V vs Ag/AgCl, with characteristic of an irreversible process. The study of the influence of the pH of the medium showed that pH 7.0 was the most suitable for work, since it presented higher peak current intensity. The analysis of the sweep speed variation showed that the peak current varies linearly with the square root of the sweep speed, indicating that the process is diffusion controlled (peak 1 at 0.80 V). The studies with square wave voltammetry (selected technique for the development of the methodology) had as optimized parameters f = 100 s-1, a=90 mV and ΔEs = 8 mV. After optimizing the parameters, the analytical curve was constructed for kaempferitrin in the concentration range from 3.4 x10-6 mol L-1 to 5.8 x10-5 mol L-1 with linearity of 0.99, the limits of detection and quantification were 3.6x10-6 mol L-1 and 1.2x10-5 mol L-1, respectively. In parallel, tests were performed with a pencil graphite electrode, where the voltammetric profile of kaempferitrin was similar to that observed with the BDD electrode. The detection and quantification limits obtained were 1.1x10-5 and 3.6x10-5, respectively. However, the BDD electrode was selected for the quantification of kaempferitrin in Bauhinia forficata, as it presented better repeatability of the results. A concentration of 20 mg L-1 of kaempferitrin was found in 2g of dried pata-de-vaca leaf sample. Finally, tests were carried out on two other flavonoids (chrysin and apeginin) to compare and propose an oxidation mechanism for kaempferitrin. The electrochemical studies allowed the determination of kaempferitrin in infusions of Bauhinia forficata and also to propose an oxidation mechanism for this compound on BDD electrode.
In this work, the electrochemical behavior of the glycosylated flavonoid kaempferitrin was studied and an electroanalytical methodology was developed for its determination in infusions of Bauhinia forficata, using a boron-doped diamond electrode (BDD). The study of the flavonoid's electrochemical behavior in cyclic voltammetry showed two oxidation peaks, one at 0.80 V vs Ag/AgCl, and another around 1.0 V vs Ag/AgCl, with characteristic of an irreversible process. The study of the influence of the pH of the medium showed that pH 7.0 was the most suitable for work, since it presented higher peak current intensity. The analysis of the sweep speed variation showed that the peak current varies linearly with the square root of the sweep speed, indicating that the process is diffusion controlled (peak 1 at 0.80 V). The studies with square wave voltammetry (selected technique for the development of the methodology) had as optimized parameters f = 100 s-1, a=90 mV and ΔEs = 8 mV. After optimizing the parameters, the analytical curve was constructed for kaempferitrin in the concentration range from 3.4 x10-6 mol L-1 to 5.8 x10-5 mol L-1 with linearity of 0.99, the limits of detection and quantification were 3.6x10-6 mol L-1 and 1.2x10-5 mol L-1, respectively. In parallel, tests were performed with a pencil graphite electrode, where the voltammetric profile of kaempferitrin was similar to that observed with the BDD electrode. The detection and quantification limits obtained were 1.1x10-5 and 3.6x10-5, respectively. However, the BDD electrode was selected for the quantification of kaempferitrin in Bauhinia forficata, as it presented better repeatability of the results. A concentration of 20 mg L-1 of kaempferitrin was found in 2g of dried pata-de-vaca leaf sample. Finally, tests were carried out on two other flavonoids (chrysin and apeginin) to compare and propose an oxidation mechanism for kaempferitrin. The electrochemical studies allowed the determination of kaempferitrin in infusions of Bauhinia forficata and also to propose an oxidation mechanism for this compound on BDD electrode.