Determinação enzimática de dopamina em formulações farmacêuticas utilizando sistema de análise por injeção em fluxo com extrato bruto de abacate (Persea americana)

Abstract

Recebido em 16/4/02; aceito em 4/9/02 ENZIMATIC DETERMINATION OF DOPAMINE IN PHARMACEUTICAL FORMULATIONS USING A FLOW INJECTION ANALYSIS SYSTEM WITH AVOCADO (Persea americana) CRUDE EXTRACT. In this work, a spectrophotometric flow injection analysis system using a crude extract of avocado (Persea americana) as a source of polyphenol oxidase to dopamine determination was developed. The substrates and enzyme concentrations from 2.4x10-7 to 5.3x10-4 mol L-1 and 28 to 332 units mL-1 were evaluated, respectively. In addition, the FIA parameters such as sample loop (50 to 500 µL), flow rate (1.4 to 4.3 mL min-1) and reactor length (100 to 500 cm) were also evaluated in a 0.1 mol L-1 phosphate buffer solution (pH 7.0). Dopamine solution concentrations were determined using 277 units mL-1 enzyme solution, 400 mL enzyme loop, 375 µL sample loop, 2.2 mL min-1 flow rate and a reactor of 350 cm. The analytical curve showed a linearity from 5.3x10-5 to 5.3x10-4 mol L-1 dopamine with a detection limit of 1.3x10-5 mol L-1. The analytical frequency was 46 h-1 and the RSD lower than 0.5% for 5.3x10-4 mol L-1 dopamine solution (n=10). A paired t-test showed that all results obtained for dopamine in commercial formulations using the proposed flow injection procedure and a spectrophotometric procedure agree at the 95% confidence level.

Gene expression of antioxidant enzymes and coffee seed quality during pre- and post-physiological maturity

“…In coffee, the concentrations of antioxidant enzymes vary in accordance with the different tissues (Brandão Junior et al, 2002;Lupetti et al, 2003;Lima et al, 2004). Reduced activity of the enzymes is related to a loss of seed viability (Hoekstra et al, 1997) caused by an increase in lipid peroxidation and free radical accumulation during dehydration, the consequential reduction in berry quality (Brandão Junior et al, 1999Lima et al, 2004), and loss of biological activity in seeds that are sensitive to desiccation (Nkang et al, 2000;Alscher et al, 2002).…”

“…Enzymes, including catalase (CAT) and superoxide dismutase (SOD), are protective systems that take part in removing reactive oxygen species (ROS) (Kibinza et al, 2011). The polyphenol oxidase (PPO) enzyme in coffee berries is bonded to the cell membranes and, in the presence of oxygen, causes oxidation of certain compounds (Lupetti et al, 2003) such as quinones (Pimenta et al, 2004).…”

Nota Científica: Caracterização físico-química do óleo de abacate extraído por centrifugação e dos subprodutos do processamento

“…Segundo Tango et al (2004), as sementes dos frutos das cultivares ricas em óleo nas polpas apresentam teores de amido acima da média geral. Quanto à fase de sólidos, que contempla a polpa de abacate após extração dos lipídios, observa-se em maior volume a presença de carboidratos, com rápido escurecimento perceptível a olho nu, provocado pela ação da enzima polifenoloxidase, presente em alta concentração no abacate, conforme relatado por Lupetti et al (2003).…”

Theoretical Study of the Binuclear Complexes of Manganese (Ii) With Ligand 2-Hydroxybenzylglycine, Possibles Mimics for Catechol Oxidase

“…4 No trabalho de Lupetti e colaboradores a enzima foi usada para determinação de dopamina em formulações farmacêuti-cas. 5 Outra possível aplicação é como agente oxidante de compostos poluentes em efluentes de despolpa do café, no caso, catecóis. 6 Muitas vezes é praticamente impossível estudar teoricamente a própria enzima, o que acaba gerando a busca de moléculas que venham mimetizar a ação destas enzimas.…”