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8-Chlorotheophylline

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Jhonys Machado Freitas – One of the best experts on this subject based on the ideXlab platform.

  • Simultaneous determination of three species with a single-injection step using batch injection analysis with multiple pulse amperometric detection.
    Talanta, 2016
    Co-Authors: Jhonys Machado Freitas, Thiago Da Costa Oliveira, Denise Tofanello Gimenes, Rodrigo A.a. Munoz, Eduardo M. Richter

    Abstract:

    In this work, the possibility of simultaneous determination of three compounds with a single-injection step using batch injection analysis with multiple pulse amperometric detection (BIA-MPA) is demonstrated for the first time. A sequence of three potential pulses (+1.25 V, +1.60 V, and +1.80 V) was applied with the acquisition of three separate amperograms. 8-Chlorotheophylline was detected selectively at +1.25 V, both 8-Chlorotheophylline and pyridoxine at +1.60V and 8-Chlorotheophylline, pyridoxine, and diphenhydramine at +1.80 V. Subtraction between the currents detected at the three amperograms (with the help of correction factors) was used for the selective determination of pyridoxine and diphenhydramine. The proposed method is simple, inexpensive, fast (60 injections h(-1)), and present selectivity for the determination of the three compounds in pharmaceutical samples, with results similar to those obtained by HPLC (95% confidence level).

  • Fast determination of diphenhydramine, pyridoxine, and 8-Chlorotheophylline by capillary electrophoresis with capacitively coupled contactless conductivity detection
    Analytical Methods, 2016
    Co-Authors: Michelle M. A. C. Ribeiro, Jhonys Machado Freitas, Rodrigo A.a. Munoz, Claudimir Lucio Do Lago, Eduardo M. Richter

    Abstract:

    This work reports a new and fast method for the simultaneous determination of diphenhydramine (DIP), pyridoxine (PYR), and 8-Chlorotheophylline (CTP) by capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D). Samples containing DIP as the cation and both PYR and CTP as anions were analysed simultaneously in a single run (in less than 3 minutes). The separation by CE-C4D was achieved on a fused silica capillary (50 cm length – 40 cm effective, 50 μm i.d.) using an optimized background electrolyte (BGE) composed of 20 mmol L−1 boric acid + NaOH (pH 9.0). Detection limits were 0.6, 1.3 and 1.3 μmol L−1 for DIP, PYR and CTP, respectively. The proposed CE-C4D method is inexpensive, simple, fast (20 injections per h), environmentally friendly (minimal waste generation) and accurate (recovery values between 98 and 100%). The results obtained by the CE-C4D method were statistically similar to those obtained by HPLC (95% confidence level).

  • Determinação estequiométrica de dimenidrinato e simultânea de 8-cloroteofilina, difenidramina e piridoxina usando análise por injeção em batelada com detecção amperométrica de múltiplos pulsos
    Universidade Federal de Uberlândia, 2015
    Co-Authors: Jhonys Machado Freitas

    Abstract:

    No presente trabalho investigou-se a potencialidade do sistema de Análise por Injeção em Batelada com detecção por Amperometria de Múltiplos Pulsos (BIA-MPA) usando diamante dopado com boro (BDD) na determinação simultânea de 8-cloroteofilina (CTF) e difenidramina (DIF), e destes simultaneamente com piridoxina (PIR) ou cafeína (CAF), em formulações farmacêuticas.
    A determinação simultânea de CTF e DIF por BIA-MPA foi realizada através da aplicação de três pulsos de potenciais em função do tempo ao eletrodo de BDD usando NaAc/HAc 0,05 mol L-1(pH = 4,7) como eletrólito suporte. Em +1,35 V/50ms, CTF foi detectada (oxidação) sem a interferência de DIF. Em +1,80 V/50ms, ambos os compostos (CTF + DIF) foram oxidados. A corrente de oxidação da DIF foi obtida pela subtração entre as correntes detectadas em ambos os pulsos de potenciais mediante uso de um fator de correção. O pulso de 0,7 V/200 ms foi aplicado para evitar a contaminação/passivação da superfície do eletrodo de trabalho (BDD). O método proposto apresentou estabilidade (RSD = 2,4 e 2,5% para CTF e DIF, respectivamente; n=20), alta frequência analítica (70 injeções h-1), faixa linear de resposta entre 10 e 60 μmol L-1 (r > 0,998) e os LD e LQ de 2,2 e 7,3 μmol L-1 para CTF e em 0,5 e 1,7 μmol L-1 para DIF, respectivamente. O método proposto foi aplicado na determinação simultânea de CTF e DIF em formulações farmacêuticas e os resultados obtidos foram similares ao obtidos por HPLC, a um nível de confiança de 95%.
    O mesmo sistema (BIA-MPA) também foi adaptado para a determinação simultânea de PIR, CTF e DIF. Neste método, os seguintes pulsos de potenciais foram aplicados sequencialmente ao eletrodo de BDD usando H2SO4 0,1 mol L-1 como eletrólito suporte: a) + 1,25 V/50 ms: oxidação da CTF sem interferência dos demais compostos; b) + 1,60 V/50 ms: oxidação de CTF e PIR sem a interferência de DIF; c) + 1,80 V/50 ms: oxidação de CTF, PIR e DIF; d) + 1,0 V (150 ms): aplicado para evitar a contaminação do eletrodo de trabalho de BDD. Expressões matemáticas simples e fatores de correção foram utilizados para obtenção das correntes de oxidação de cada analito. Este método proposto apresentou os seguintes resultados: estabilidade (RSD= 0,9, 1,5 e 1,5% para CTF, PIR e DIF, respectivamente; n=20), alta frequência analítica (~60 injeções h-1), faixa linear de resposta entre 20,0 e 60,0 μmol L-1 para CTF e DIF e entre 10,0 e 30,0 μmol L-1 para PIR e os LD e LQ de 0,19 e 0,62 μmol L-1 para CTF, 0,54 e 1,81 μmol L-1 para PIR e 0,18 e 0,60 μmol L-1 para DIF. O método proposto foi aplicado na determinação simultânea de CTF, PIR e DIF em amostras farmacêuticas comerciais e os resultados obtidos foram similares ao obtidos por HPLC a um nível de confiança de 95%.
    Um terceiro método (similar ao segundo) foi proposto para a determinação simultânea de CAF, CTF e DIF. Os pulsos de potencial aplicados foram + 1,10 V (oxidação da CTF), +1,40 V (oxidação de CTF e CAF) e + 1,70 V (oxidação de CTF, CAF e DIF) usando NaAc/HAc 0,05 mol L-1(pH = 4,7) como eletrólito suporte. O sistema BIA-MPA proposto apresentou alta frequência analítica (120 injeções h-1), elevada precisão (DPRs < 1,0%, n = 20) e baixos valores de LD e LQ, (0,31 e 1,03 μmol L-1 para CTF; 0,49 e 1,63 μmol L-1 para CAF e 0,76 e 4,09 μmol L-1 para DIF, respectivamente). O método proposto foi aplicado na determinação de CTF, CAF e DIF em uma amostra farmacêutica manipulada e os resultados obtidos foram similares ao obtidos por HPLC, a um nível de confiança de 95%.In this work, the potentiality of batch injection analysis with multiple pulse amperometric (BIA-MPA) detection using boron doped diamond (BDD) electrode was investigated for simultaneous determination of 8-Chlorotheophylline (CTF) and diphenhydramine (DIP), and these simultaneously with pyridoxine (RIP) or caffeine (CAF) in pharmaceutical formulations.
    The simultaneous determination of (CTF) and (DIF) was performed with the application of three sequential pulses in function of time to the BDD electrode using NaAc/HAc 0.05 mol L-1(pH = 4.7) as supporting electrolyte. At 1.35 V/50 ms, CTF was detected (oxidation) without interference of DIF. At 1.80 V/50 ms, both compounds (CTF + DIF) were oxidized. The current of DIF can then be obtained by subtraction of the currents detected during application of both potential pulses using a correction factor. The potential pulse of 0.7 V/200 ms was applied to avoid contamination/passivation of the BDD electrode surface. The proposed method presented stability (RSD = 2.4 e 2.5% for CTF e DIF, respectively; n=20), high analytical frequency (70 injections h-1), linear concentration range between and LOD and DOQ of 2.2 and 7.3 μmol L-1 for CTF and 0.5 e 1.7 μmol L-1 for DIF, respectively. The proposed method was used for simultaneous determination of CTF and DIF in pharmaceutical formulations and the obtained results were similar to those obtained by HPLC (confidence interval = 95%).
    The same system (BIA-MPA) has also been adapted for simultaneous determination of PIR, CTF e DIF. In this method, the following potential pulses were applied sequentially to the BDD working electrode using H2SO4 0.1 mol L-1 as supporting electrolyte: (a) + 1.25 V/50 ms: oxidation of CTF without interference of the other compounds; b) + 1.60 V/50 ms: oxidation of CTF e PIR without interference of DIF; c) + 1.80 V/50 ms: oxidation of CTF, PIR and, DIF; d) + 1.0 V (150 ms): applied to avoid contamination/passivation of the BDD electrode surface. Simple mathematical expressions and correction factors were used to access the oxidation current of each analyte. The proposed method presented the following results: stability (RSD= 0.9, 1.5 e 1.5% for CTF, PIR and DIF, respectively; n=20), high analytical frequency (~60 injections h-1), linear concentration range between and 20.0 and 60.0 μmol L-1 for CTF and DIF and between 10.0 and 30.0 μmol L-1 for PIR and the LD and LQ of 0.19 and 0.62 μmol L-1 for CTF, 0.54 and 1.81 μmol L-1 for PIR and 0.18 e 0.60 μmol L-1 for DIF. The proposed method was applied for simultaneous determination of CTF, PIR and DIF in pharmaceutical samples and the obtained results were similar to those obtained by HPLC (confidence interval = 95%).
    A third method (similar to the second) was proposed for simultaneous determination of CAF, CTF e DIF. The applied potential pulses were + 1.10 V (CTF oxidation), +1.40 V (oxidation of CTF and CAF) and, + 1.70 V (oxidation of CTF, CAF and, DIF) using NaAc/HAc 0.05 mol L-1(pH = 4.7) as supporting electrolyte. The proposed BIA-MPA system presented high analytical frequency (120 injections h-1), precision (RSDs < 1.0%, n = 20) and low LD and LQ values (0.31 e 1.03 μmol L-1 for CTF, 0.49 and 1.63 μmol L-1 for CAF and 0.76 and 4.09 μmol L-1 for DIF, respectively. The proposed method was applied for determination of CTF, CAF and, DIF in pharmaceutical sample and the obtained results were similar to those obtained by HPLC (confidence interval = 95%)

Simone Beninati – One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of polyamines as marker of melanoma cell proliferation and differentiation by an improved high-performance liquid chromatographic method
    Amino Acids, 2019
    Co-Authors: Bruno Provenzano, Alessandro Lentini, Roberta Tatti, Angelo Martino, Ilaria Borromeo, Carlo Mischiati, Giordana Feriotto, Cinzia Forni, Claudio Tabolacci, Simone Beninati

    Abstract:

    The differentiation therapy is focused on the identification of new agents able to impair the proliferative and metastatic potential of cancer cells through the induction of differentiation. Although several markers of cell differentiation on tumor cells have been identified, their causal relationship with neoplastic competence has not been characterized in sufficient detail to propose their use as new pharmacological targets useful for the design of new differentiation agents. Polyamine level in cancer cells and in body fluids was proposed as potential marker of cell proliferation and differentiation. The main advantage of this marker is the possibility to evaluate the antineoplastic activity of new drugs able to induce cell differentiation and consequently to inhibit tumor growth and metastasis. The presented report shows a simply and highly reproducible reverse-phase high-performance liquid chromatographic (HPLC) method for the determination of ortho -phthalaldehyde (OPA) derivatives of polyamines: putrescine (PUT), cadaverine (CAD), spermidine (SPD) and spermine (SPM). The novelty of this method is the fluorescence response for OPA-derivate of SPM, generally low in other procedures, that has been significantly improved by the use of a fully endcapped packing material with minimal silanol interactions. The limits of detection for PUT, CAD, SPD and SPM were 0.6, 0.7, 0.8, and 0.4 pmol/mL, respectively. The analysis time was ≤ 20 min, and the relative recovery rate was of about 97%. To verify the usefulness of this method, it has been validated in a murine melanoma cell line (B16-F10) treated with two theophylline derivatives (namely 8-Chlorotheophylline and 8-bromotheophylline). These two compounds increased the activity of tissue transglutaminase (TG2) and the synthesis of melanin, two recognized markers of melanoma cell differentiation, and significantly reduced the levels of intracellular polyamines.

Y S Chang – One of the best experts on this subject based on the ideXlab platform.

  • Solid-phase extraction for the determination of caffeine in traditional Chinese medicinal prescriptions containing Theae folium by high performance liquid chromatography.
    Journal of Pharmaceutical and Biomedical Analysis, 1999
    Co-Authors: K C Wen, Y S Chang

    Abstract:

    A high performance liquid chromatographic method in combination with C-18 reverse phase solid-phase extraction (SPE) was developed for determination of caffeine (CA) in traditional Chinese medicinal prescriptions which contain Theae folium. The frequently used prescriptions include Shin-Yi-San, Chuan-Chyong-Char-Tyau-San, Tsang-Eel-San, San-Hwang-Shyr-Gau-Tang, Tzy-Shenn-Ming-Mu-Tang and Shiang-Chyong-San. The present HPLC system uses a Merck RP-select B column by isocratic elution with methanol and 1% (v/v) acetic acid (1:4) as the mobile phase and detected at UV 270 nm. 8-Chlorotheophylline was used as an internal standard. The extracts of prescriptions were treated by Supelclean LC-18 SPE tube for eliminating interferences. Blank decoctions of each prescription were also examined as a test for interferences. The recoveries of caffeine from the Chinese medicinal prescriptions ranged from 88.5 to 92.3%. The relative standard deviations of caffeine ranged between 0.86 and 1.97% (intraday) and 1.04 and 3.90% (interday). The contents of caffeine in standard decoctions ranged from 13.98 to 19.62 mg g^(-1). © 1999 Elsevier Science B.V. All rights reserved.

  • Solid-phase extraction for the determination of caffeine in traditional Chinese medicinal prescriptions containing Theae folium by high performance liquid chromatography.
    Journal of Pharmaceutical and Biomedical Analysis, 1999
    Co-Authors: K C Wen, Y S Chang

    Abstract:

    A high performance liquid chromatographic method in combination with C-18 reverse phase solid-phase extraction (SPE) was developed for determination of caffeine (CA) in traditional Chinese medicinal prescriptions which contain Theae folium. The frequently used prescriptions include Shin-Yi-San, Chuan-Chyong-Char-Tyau-San, Tsang-Eel-San, San-Hwang-Shyr-Gau-Tang, Tzy-Shenn-Ming-Mu-Tang and Shiang-Chyong-San. The present HPLC system uses a Merck RP-select B column by isocratic elution with methanol and 1% (v/v) acetic acid (1:4) as the mobile phase and detected at UV 270 nm. 8-Chlorotheophylline was used as an internal standard. The extracts of prescriptions were treated by Supelclean LC-18 SPE tube for eliminating interferences. Blank decoctions of each prescription were also examined as a test for interferences. The recoveries of caffeine from the Chinese medicinal prescriptions ranged from 88.5 to 92.3%. The relative standard deviations of caffeine ranged between 0.86 and 1.97% (intraday) and 1.04 and 3.90% (interday). The contents of caffeine in standard decoctions ranged from 13.98 to 19.62 mg g(-1).