Flow Injection Spectrophotometric Determination of L-Dopa and Carbidopa in Pharmaceutical Formulations Using a Crude Extract of Sweet Potato Root [Ipomoea batatas (L.) Lam.] as Enzymatic Source

Fatibello‐Filho, Orlando; Vieira, Iolanda Cruz

doi:10.1039/a606852i

Cited by 67 publications

(35 citation statements)

References 31 publications

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“…A similar phenomenon is also observed in the presence of Zn 2+ . 51,52 The formation rate of DC from DOPA oxidation catalyzed by iron in the presence of a great quantity of aluminum approximates to that in the absence of aluminum in the early reaction process. However, aluminum can keep the catalytic ability of iron for more time and the formation rate of DC catalyzed by iron in the presence of aluminum decreases more slowly than in the absence of aluminum ( Fig.…”

Section: Aluminum Facilitation Of Iron-mediated Dopa Oxidationmentioning

confidence: 99%

Aluminum Facilitation of the Iron-Mediated Oxidation of DOPA to Melanin

2004

ANAL. SCI.

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Aluminum, a trivalent cation unable to undergo redox reactions, is shown to faciliate iron-initiated DOPA oxidation in the melanin pathway under acidic condition of pH 5.5, which is a favored medium for aluminum facilitation of iron-induced lipid peroxidation. In the process of oxidation of DOPA to melanin in the presence of the metal ions, Fe 3+ and H2O2 oxidize DOPA to dopachrome (DC), then Al 3+ catalyzes the conversion of DC to 5,6-dihydroxyindole (DHI) and finally Fe 3+ oxidizes DHI to indole-5,6-quinone (IQ), which polymerizes immediately to melanochrome and melanin. The reactions involve the intermediate complexes of metal ions and DOPA or its derivative. The present results indicate that aluminum can enhance the oxidative stress on iron-mediated DOPA oxidation in melanin pathway under acidic condition through the cooperation of iron and aluminum ions.

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Section: Aluminum Facilitation Of Iron-mediated Dopa Oxidationmentioning

confidence: 99%

Aluminum Facilitation of the Iron-Mediated Oxidation of DOPA to Melanin

2004

ANAL. SCI.

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“…Cross-linked polyvinylpyrrolidone was purchased from Acros Chemical Company and purified as described in the literature. 34 4-Aminoantipyrine was purchased from Merck and its stock solution was prepared in water.…”

Section: Reagentsmentioning

confidence: 99%

“…In recent years the use of plant tissue materials and crude extracts of various vegetables as novel biocatalysts has also received considerable interest for replacing isolated enzymes. [30][31][32][33][34][35][36][37] The use of such biological materials is very attractive because of their simplicity, high stability, very low cost and fewer cofactor requirements in comparison with the pure enzymes.…”

mentioning

confidence: 99%

Application of Crude Extract of Kohlrabi (Brassica oleracea gongylodes) as a Rich Source of Peroxidase in the Spectrofluorometric Determination of Hydrogen Peroxide in Honey Samples

2006

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Crude extract of kohlrabi (Brassica oleracea gongylodes) was prepared by a simple procedure and its enzymatic activity and total protein concentration were determined. It was found that this crude extract is a rich source of peroxidase (POx) and has high specific activity. Cross-linked polyvinylpyrrolidone was used as a stabilizer in the preparation of the crude extract. The POx activity of kohlrabi crude extract did not vary for at least 2 months when deoxygenated and stored at 4˚C. This extract was applied for the spectrofluorometric determination of hydrogen peroxide using homovanillic acid as a fluorogenic substrate. POx catalyzes the hydrogen peroxide oxidation of homovanillic acid to produce a dimer which shows strong fluorescence at 420 nm with excitation at 312 nm. In the optimum conditions, the calibration graph for hydrogen peroxide was linear up to 190 ng mL -1 , with a detection limit of 4.4 ng mL -1 . The relative standard deviation (RSD) was 1.48% for 50 ng mL -1 hydrogen peroxide. The proposed method was successfully applied to the determination of hydrogen peroxide in honey. The concentration-time profile of H2O2 produced upon dilution of honey was studied and H2O2 contents of some different honeys from various areas of Iran were determined.

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“…4,5 Adrenaline reference solutions from 6.0 x 10 -6 to 6.0 x 10 -4 mol L -1 and dopamine reference solutions from 6.0 x 10 -6 to 3.0 x 10 -4 mol L -1 were prepared from stock solutions in 0.1 mol L -1 phosphate buffer solutions at pH 7.0 and pH 6.0, respectively. In the construction of the biosensors an Acheson 38 graphite powder from Fisher and mineral oil from Sigma were used throughout.…”

Section: Reagents and Solutionsmentioning

confidence: 99%

“…3 On the other hand, catecholamines are present in relatively larger amounts in pharmaceuticals and much effort has been done to develop precise, accurate, rapid and simple analytical procedures. 4,5 Electroanalytical techniques applied to the determination of catecholamines are good alternatives. [6][7][8][9] Nevertheless, the selectivity can be poor, unless the electrodes are conveniently modified.…”

Section: Introductionmentioning

confidence: 99%

Determination of catecholamines in pharmaceutical formulations using a biosensor modified with a crude extract of fungi laccase (Pleurotus ostreatus)

Leite¹,

Fatibello‐Filho²,

Barbosa-Dekker³

2003

J. Braz. Chem. Soc.

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Um biossensor de pasta de carbono modificado com extrato bruto enzimático do fungo Pleurotus ostreatus como fonte de lacase é proposto para a determinação de catecolaminas em formulações farmacêuticas. Essa enzima catalisa a oxidação de adrenalina ou dopamina nas quinonas correspondentes e a corrente obtida na redução eletroquímica de cada um dos produtos é relacionada a concentração dessas catecolaminas em solução da amostra. O efeito da concentração de lacase de 0,29 a 1,8 U/mg de pasta de carbono, do pH de 3,0 a 8,0, da velocidade de varredura de 10 a 40 mV s -1 e amplitudes de pulso de potencial de 10 a 60 mV sobre a resposta voltamétrica de pulso diferencial foi investigado. O desvio padrão relativo foi menor que 1,8% para solução de hidroquinona 2,8 x 10 -4 mol L -1 em pH 7 (n=10). Recuperações variando de 97,3 a 101% para adrenalina e de 95,8 a 102% para dopamina foram obtidas. As curvas analíticas foram lineares no intervalo de concentração de adrenalina de 6,0 x 10 -5 a 7,0 x 10 -4 mol L -1 e de 7,0 x 10 -5 a 4,0 x 10 -4 mol L -1 para dopamina, com limites de detecção de 7,9 x 10 -6 mol L -1 e 9,8 x 10 -6 mol L -1 , respectivamente. Esse biossensor foi empregado para a determinação de adrenalina e dopamina em formulações farmacêuticas. Os resultados obtidos com o biossensor para a determinação dessas catecolaminas em formulações farmacêuticas estão em concordância a um nível de confiança de 95% com o procedimento da Farmacopéia americana.A carbon paste biosensor modified with a crude enzymatic extract of the Pleurotus ostreatus fungi as a laccase source is proposed for catecholamine determination in pharmaceutical formulations. This enzyme catalyzes the oxidation of adrenaline or dopamine in the corresponding quinones and the current obtained in the electrochemical reduction of each of the products is related to the concentration of these catecholamines in the sample solution. The effect of the laccase concentration from 0.29 to 1.8 U/mg of carbon paste, pH from 3.0 to 8.0, scan rate from 10 to 40 mV s -1 and potential pulse amplitude from 10 to 60 mV on the differential pulse voltammetric response was investigated. The relative standard deviation was smaller than 1.8% for a 2.8 x 10 -4 mol L -1 hydroquinone solution at pH 7.0 (n=10). Recoveries varied from 97.3 to 101% for adrenaline and from 95.8 to 102% for dopamine. The analytical curves were rectilinear in the adrenaline concentration range from 6.0 x 10 -5 to 7.0 x 10 -4 mol L -1 and 7.0 x 10 -5 to 4.0 x 10 -4 mol L -1 for dopamine, with detection limits of 7.9 x 10 -6 mol L -1 and 9.8 x 10 -6 mol L -1 , respectively. This biosensor was used for adrenaline and dopamine determinations in pharmaceutical formulations. The results obtained using the proposed biosensor are in close agreement with those obtained using an American Pharmacopoeia procedure at a 95% confidence level. Keywords: laccase, Pleurotus ostreatus, catecholamines, biosensor IntroductionCatecholamines play an important role in the central nervous system as neurotransmitters. They als...

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Flow Injection Spectrophotometric Determination of L-Dopa and Carbidopa in Pharmaceutical Formulations Using a Crude Extract of Sweet Potato Root [Ipomoea batatas (L.) Lam.] as Enzymatic Source

Cited by 67 publications

References 31 publications

Aluminum Facilitation of the Iron-Mediated Oxidation of DOPA to Melanin

Aluminum Facilitation of the Iron-Mediated Oxidation of DOPA to Melanin

Application of Crude Extract of Kohlrabi (Brassica oleracea gongylodes) as a Rich Source of Peroxidase in the Spectrofluorometric Determination of Hydrogen Peroxide in Honey Samples

Determination of catecholamines in pharmaceutical formulations using a biosensor modified with a crude extract of fungi laccase (Pleurotus ostreatus)

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