Determination of etoricoxib in human plasma using automated on-line solid-phase extraction coupled with LC-APCI/MS/MS

A liquid chromatography-tandem mass spectrometry method with atmospheric pressure chemical ionization (LC-APCI/MS/MS) was validated for the determination of etoricoxib in human plasma using antipyrin as internal standard, followed by on-line solid-phase extraction. The method was performed on a Luna C18 column and the mobile phase consisted of acetonitrile:water (95:5, v/v)/ammonium acetate (pH 4.0; 10 mM), run at a flow rate of 0.6 mL/min. The method was linear in the range of 1-5000 ng/mL (r²>0.99). The lower limit of quantitation was 1 ng/mL. The recoveries were within 93.72-96.18%. Moreover, method validation demonstrated acceptable results for the precision, accuracy and stability studies.

Desenvolvimento e validação de um método analítico rápido por cromatografia líquida de alta eficiência para determinação de nimesulida em estudos de liberação in vitro

A high performance liquid chromatography (HPLC) method has been developed for a rapid determination of nimesulide in dissolution studies. Nimesulide was analyzed using 5 µm Lichrospher® RP-18 column (125 x 4 mm i.d.) and mobile phase acetonitrile: phosphate buffer pH=6.0 (55:45) at a flow-rate of 1.0 mL min-1. Detection was carried out at 300 nm at 25 ºC. The method was applied to analysis of nimesulide in in vitro release studies and showed a rapid and efficient analytical alternative for evaluation of dissolution profile of nimesulide.

Estudo da degradação fotocatalítica de dimetil dissulfeto: avaliação estatistica do efeito do pH da temperatura e concentração do contaminante orgânico

This work aimed to assess the photocatalytic degradation of a model odor compound (dimethyl disulfide, DMDS), found in liquid and gaseous wastes of plants for processing poultry byproducts. The effect of pH and temperature on adsorption and photocatalytic degradation was evaluated through factorial experimental designs. The results suggest the presence of an optimum region for adsorption, at 45.0 ºC and pH 4.0. In the photocatalytic runs an optimum for temperature and pH was also observed. At 45 ºC and pH 4.0 the removal of DMDS was 99% after 60 min of irradiation.

Voltammetric determination of sibutramine in beverages and in pharmaceutical formulations

A simple and sensitive method has been proposed for the determination of sibutramine-HCl in energy drinks, green tea and pharmaceutical formulations using differential pulse voltammetry performed on a hanging mercury drop electrode. In the chosen experimental condition (Mcllvaine pH 4.0 buffer, 50 mV pulse amplitude and 40 mV s-1 scan velocity), sibutramine-HCl presented a reversible behavior and a peak maximum at -80 mV. Detection limit was 0.4 mg L-1 and the working linear range extended up to 33.3 mg L-1 (r = 0.99). Analysis of real and fortified samples enabled recoveries between 91 and 102%. The electroanalytical method was compared with a HPLC method which indicated it accuracy.

Influência do pH nas propriedades físico-químicas, térmicas e mecânicas de filmes de poli(vinil álcool)/poli(ácido acrílico)/aciclovir

Drug-loaded films represent an alternative method for the treatment of skin lesions caused by Herpes simplex, since they facilitate delivery of the drug directly at the site of lesion. The objective of this work was to prepare PVA/PAA films containing AC at pH 2.0 and 4.0. The results show that the pH of the film preparations influences the polymer¾drug interaction kinetic order and the degree of swelling. The mechanism of release of AC from the films obtained at pH 4.0 was anomalous, whereas for the films prepared at pH 2.0 the release followed zero-order kinetics.

Stability-indicating RP-HPLC method for simultaneous determination of gatifloxacin and flurbiprofen in binary combination

A stability-indicating RP-HPLC method is presented for determination of gatifloxacin and flurbiprofen in binary combination. Gatifloxacin, flurbiprofen and their degradation products were detected at 254 nm using a BDS Hypersil C8 (250 X 4.6 mm, 5 µm) column and mixture of 20 mM phosphate buffer (pH 3.0) and methanol 30:70 v/v as mobile phase. Response was linear over the range of 15-105 mg mL-1 for gatifloxacin (r² > 0.998) and of 1.5-10.5 mg mL-1 for flurbiprofen (r² > 0.999). The developed method efficiently separated the analytical peaks from degradation products (peak purity index > 0.9999). The method developed can be applied successfully for determination of gatifloxacin and flurbiprofen in human serum, urine, pharmaceutical formulations, and their stability studies.

AVALIAÇÃO DO RADICAL N,N-DIETIL-1,4-FENILENODIAMINO (DEPD•+) COMO SONDA ESPECTROFOTOMÉTRICA PARA DETERMINAÇÃO DA CAPACIDADE ANTIOXIDANTE EM BEBIDAS

AbstractMany well-established methods for determining the antioxidant capacities in several samples have been described in literature. However, DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)) are the main two methods that utilize radicals as spectrophotometric probes for analysis. Nevertheless, these methods have certain limitations because of their slower kinetics, solvent polarity effects, the hydrophilicity and lipophilicity of the compounds, chemical costs, etc. In this study, a spectrophotometric method for determining the antioxidant capacity in beverages was developed based on an exploration of the cation radical derived from DEPD. This method was based on the oxidation of aromatic amines with Fe(III) ions at pH 4.0, which leads to their corresponding purple cation radicals (DEPD•+) with λmax values at 500 and 540 nm. The addition of an antioxidant after the formation of the radical leads to a reduction in color intensity that is proportional to the antioxidant concentration in the medium. Results obtained using this method were compared with the Folin-Ciocalteau, ABTS and DPPH methods in terms of applications in wines, teas, and infusions samples. Linear correlation analysis at a 95% confidence level was employed to compare the results, which were in good agreement with a correlation coefficient of r > 0.9000. Thus, the developed method was simple, accurate, and consistent with other assays for the determination of the total amount of phenolic compounds and antioxidant capacity.

Simulação das perdas de água por evaporação e arraste, no aspersor NY-7 (4,6 mm x 4,0 mm), em sistemas de aspersão convencional

As perdas de água por evaporação e arraste em sistemas de irrigação por aspersão podem assumir valores consideráveis, reduzindo a eficiência do sistema. Os objetivos do presente trabalho foram avaliar a capacidade preditiva de cinco modelos empíricos para estimar perdas de água por evaporação e arraste em aspersores modelo NY-7 (bocais de 4,6 mm x 4,0 mm), trabalhando sob diferentes condições operacionais e ambientais, e ajustar modelos específicos para o aspersor NY-7. Comparando os resultados medidos em ensaios de campo, com os resultados simulados, foi possível concluir que os cinco modelos empíricos considerados apresentaram pouca ou nenhuma adequação, tanto para os ensaios com um único aspersor (quadrado do erro-médio de 5,27; 20,70; 5,07; 6,95 e 7,06% para os modelos empíricos 1; 2; 3; 4 e 5, respectivamente) quanto para os ensaios com linhas laterais contendo aspersores (quadrado do erro-médio de 7,41; 24,43; 6,72; 3,16 e 2,9% para os modelos empíricos 1; 2; 3; 4 e 5, respectivamente). Comparados aos cinco modelos empíricos considerados, os novos modelos ajustados apresentaram menores erros, indicando que a aplicação de modelos empíricos deve ser limitada às condições de operação (diâmetro de bocal, pressão de operação, etc.) similares àquelas em que os modelos foram desenvolvidos.

Estudo experimental comparando o uso do 2-octil cianoAcrilato ao nylon 4-0 na sutura da pele

OBJETIVO: Comparar o 2-octil cianoacrilato com o fio de "nylon" no fechamento da pele em ratos. MÉTODOS: Vinte e cinco ratos da linhagem Wistar, foram submetidos à incisão de 3 cm de cada lado do abdome. A síntese foi feita utilizando em um dos lados o "nylon" 4.0, pontos intradérmicos, e do outro o 2-octil cianoacrilato. Após sete dias, o fio foi removido e as incisões, analisadas quanto às complicações. Após 40 dias, o resultado da cicatriz foi avaliado. Os ratos foram sacrificados, as cicatrizes foram ressecadas, fixadas e enviadas ao patologista, sem informação sobre qual o método utilizado. RESULTADOS: Houve dois óbitos durante a anestesia e um tardio. O tempo de operação foi de 136 segundos com a cola e 176 segundos, com o "nylon" (P=0,003). Dentre as 50 operações realizadas, as complicações foram: um hematoma com cada método (P=0,80), quinze deiscências da cola contra 11 do "nylon" (P=0,20), sete cicatrizes de aspecto ruim ou razoável da cola contra quatro do "nylon" (P=0,30), três infecções na cola contra duas (P=0,40). Ao exame patológico, a mediana da largura da cicatriz foi de 1.119 micra com a cola e 1.800 com o "nylon" (P=0,40). A espessura foi de 1.795 contra 1.705 micra (P=0,40). CONCLUSÃO: O 2-octil cianoacrilato apresentou o mesmo aspecto cicatricial, a mesma resistência e as mesmas complicações que a sutura com o "nylon" 4.0, porém permitindo redução no tempo cirúrgico.

Influência pH na reposta de sementes de plantas daninhas a substâncias promotoras de germinação

Determinou-se o efeito do pH na ação de algumas subst âncias promotoras de germinação em sementes de Chenopodium album L., Avena fatua L. e Rumex crispus L. A azida de sódio (A), nitrato de potássio + etileno (NE), NE + A, NE + A + tiuréia + peróxido de hidrogênio foram testados em solo (em bandej as) e em papel (in vitro) com soluções tampão em ambiente controlado. O efeito do NE no estímulo à germinação de sementes não foi afetado pelo pH na faixa de 3 a 9. A azida de sódio foi a substância que mais afetou as sementes, sendo este efeito pH dependente. Este composto foi extremamente deletério em sementes de C. album e A. fatua em solo ácido (pH 4,0), enquanto em solo básico ele estimulou a germinação em sementes de A. fatua, através da superação da dormência A combinação de NE + A em pH 6,2 inibiu a germinação de C. album e A. fatua, mostrando um antagonismo entre estes compostos. A mistura dos cinco compostos reduziu a influência do pH na ação deletéria da azida de sódio. O efeito deletério da azida foi menos afetado pela temperatura do que sua ação como superador de dormência. A solução extraída do solo não afetou a resposta de tratamentos químicos in vitro em diferentes temperaturas comparado a soluções tampão em pH semelhante. Discute-se a influência das características do solo na eficácia de substâncias químicas como superadores de dormência ou tratamentos deletérios às sementes.

Induction of neutralizing antibodies in mice immunized with scorpion toxins detoxified by liposomal entrapment

The possibility of producing neutralizing antibodies against the lethal effects of scorpion toxins was evaluated in the mouse model by immunization with an immunogen devoid of toxicity. A toxic fraction (5 mg) from the venom of the scorpion Tityus serrulatus was entrapped in sphingomyelin-cholesterol liposomes. The liposomes were treated for 1 h at 37oC with a 1% (w/w) trypsin solution in 0.2 M sodium carbonate buffer, pH 8.3. This treatment led to a strong reduction in venom toxicity. Immunization was performed as follows: mice were injected sc with 20 µg of the liposome-entrapped toxic fraction on days 1 and 21 and a final injection (20 µg) was administered ip on day 36. After injection of the immunogen, all mice developed an IgG response which was shown to be specific for the toxic antigen. The antibodies were measured 10 days after the end of the immunization protocol. In an in vitro neutralization assay we observed that pre-incubation of a lethal dose of the toxic fraction with immune serum strongly reduced its toxicity. In vivo protection assays showed that mice with anti-toxin antibodies could resist the challenge with the toxic fraction, which killed, 30 min after injection, all non-immune control mice

Immunization by subcutaneous implants of polyester-polyurethane sponges coupled with antigen

A new protocol is described for immunization of outbred Swiss mice. The procedure is based on subcutaneous implantation of antigen-coupled polyester-polyurethane sponges cut into disks of 10 mm in diameter vs 2 mm in thickness. Antigen coupling was performed by overnight incubation of the sponge with a solution of ovalbumin (Ova) (2 mg/ml) diluted in sodium carbonate buffer, pH 9.6. The amount of ovalbumin that was taken up by the sponge was between 71.4 to 82.5 µg. This was estimated by comparing the Ova absorbance at 280 nm in coating buffer solutions before and after incubation. To compare the efficiency of the proposed method, experimental groups immunized with the antigen in the presence of adjuvants (10 µg in Al(OH)3 or 100 µg in complete Freund's adjuvant (CFA)) were run in parallel. The data obtained after the 3rd week of immunization indicate that both cellular and humoral immune responses were achieved. These were assayed by antigen-induced footpad swelling and ELISA (specific antibodies), respectively. The levels of both immune responses elicited were similar to the responses observed in mice immunized with ovalbumin in the presence of Al(OH)3. The method might represent an advantage when immunizing with pathogenic antigens. Preliminary experiments have suggested that the antigen remains immobilized or bound to the sponge for a long period of time, since there is an increment on the cell population inside the sponges after boosting the animals. If so, the undesirable effects of immunization would be reduced.

A continuous fluorescent assay for the determination of plasma and tissue angiotensin I-converting enzyme activity

A continuous assay using internally quenched fluorescent peptides with the general sequence Abz-peptidyl-(Dnp)P-OH (Abz = ortho-aminobenzoic acid; Dnp = 2,4-dinitrophenyl) was optimized for the measurement of angiotensin I-converting enzyme (ACE) in human plasma and rat tissues. Abz-FRK(Dnp)P-OH, which was cleaved at the Arg-Lys bond by ACE, was used for the enzyme evaluation in human plasma. Enzymatic activity was monitored by continuous recording of the fluorescence (lambdaex = 320 nm and lambdaem = 420 nm) at 37ºC, in 0.1 M Tris-HCl buffer, pH 7.0, with 50 mM NaCl and 10 µM ZnCl2. The assays can be performed directly in the cuvette of the fluorimeter and the hydrolysis followed for 5 to 10 min. ACE measurements in the plasma of 80 healthy patients with Hip-His-Leu and with Abz-FRK(Dnp)P-OH correlated closely (r = 0.90, P < 0.001). The specificity of the assay was demonstrated by the complete inhibition of hydrolysis by 0.5 µM lisinopril or captopril. Abz-FRK(Dnp)P-OH cleavage by ACE was monitored in rat lung, kidney, heart, and liver homogenates in the presence of a cocktail of inhibitors containing trans-epoxy-succinyl-L-leucylamido-(4-guanido)-butene, pepstatin, phenyl-methylsulfonyl fluoride, N-tosyl-L-phenylalanyl-chloromethyl ketone, and N-tosyl-lysyl-chloromethyl ketone to prevent undesirable hydrolysis. ACE activity in lung, heart and kidney homogenates, but not in liver homogenates, was completely abolished by 0.5 µM lisinopril or captopril. The advantages of the method are the procedural simplicity and the high sensitivity providing a rapid assay for ACE determinations.

Efeito do pH e da hidrólise tríptica sobre as propriedades emulsionantes da globina bovina

No intuito de estudar o efeito do pH e da ação da tripsina sobre as propriedades emulsionantes da globina bovina, extraída pelo método da acetona acidificada, foram determinados neste trabalho, a capacidade emulsionante (EC), o índice de atividade emulsionante (EAI) e a estabilidade da emulsão (ES). Testaram-se os valores de pH de 3,0 a 8,0 e os tempos de hidrólise de 5,0 a 60 min. Os dados obtidos indicam que os maiores valores de EC e ES foram obtidos no pH 5,0 e 6,0, respectivamente, correspondente à faixa de alta solubilidade da proteína. Por outro lado, o EAI, além de apresentar um máximo no pH 3,0, foi igualmente elevado nos valores de pH 7,0 e 8,0, situados na zona onde a globina é praticamente insolúvel. A hidrólise tríptica, nas condições empregadas, contribuiu para melhorar a EC, em toda a faixa de pH estudada, enquanto que para o EAI somente foi benéfico em pH 4,0 e 5,0. No caso da ES, este tratamento enzimático não foi vantajoso, promovendo melhoras apenas no pH 7,0, onde a proteína é insolúvel, e somente após 60 min de hidrólise.

Estudo reológico da gelificação induzida pelo calor de proteínas do soro do leite e dos géis resultantes sob condições variadas de pH

Medidas reólogicas sob cisalhamento oscilatório foram realizadas em reômetro de tensão e deformação controladas com suspensões de concentrado de proteínas do soro do leite (WPC) a 10% (m/m) em água e a diferentes condições de pH (pH 4,0, 4,6 e 7,0). O processo de gelificação induzida pelo calor foi investigado, assim como as propriedades viscoelásticas dos géis formados a 80°C e daqueles formados após o decréscimo da temperatura a 20°C. Foi verificado que, em presença de teores significativos de sais, procedentes do próprio soro, a concentração usada nos experimentos foi suficiente para a formação de géis macroscópicos, e que o pH exerce papel importante na formação e na natureza estrutural dos géis.