RESUMEN
Dinoseb is a highly toxic pesticide of the dinitrophenol group. Its use has been restricted, but it can still be found in soils and waters in addition to being a component of related pesticides that, after ingestion by humans or animals, can originate the compound by enzymatic hydrolysis. As most dinitrophenols, dinoseb uncouples oxidative phosphorylation. In this study, distribution, lipid bilayer affinity and kinetics of the metabolic effects of dinoseb were investigated, using mainly the isolated perfused rat liver, but also isolated mitochondria and molecular dynamics simulations. Dinoseb presented high affinity for the hydrophobic region of the lipid bilayers, with a partition coefficient of 3.75×104 between the hydrophobic and hydrophilic phases. Due to this high affinity for the cellular membranes dinoseb underwent flow-limited distribution in the liver. Transformation was slow but uptake into the liver space was very pronounced. For an extracellular concentration of 10µM, the equilibrium intracellular concentration was equal to 438.7µM. In general dinoseb stimulated catabolism and inhibited anabolism. Half-maximal stimulation of oxygen uptake in the whole liver occurred at concentrations (2.8-5.8µM) at least ten times above those in isolated mitochondria (0.28µM). Gluconeogenesis and ureagenesis were half-maximally inhibited at concentrations between 3.04 and 5.97µM. The ATP levels were diminished, but differently in livers from fed and fasted rats. Dinoseb disrupts metabolism in a complex way at concentrations well above its uncoupling action in isolated mitochondria, but still at concentrations that are low enough to be dangerous to animals and humans even at sub-lethal doses.
Asunto(s)
2,4-Dinitrofenol/análogos & derivados , Enfermedad Hepática Inducida por Sustancias y Drogas/etiología , Metabolismo Energético/efectos de los fármacos , Hígado/efectos de los fármacos , Plaguicidas/toxicidad , 2,4-Dinitrofenol/química , 2,4-Dinitrofenol/toxicidad , Adenosina Trifosfato/metabolismo , Animales , Transporte Biológico , Enfermedad Hepática Inducida por Sustancias y Drogas/metabolismo , Enfermedad Hepática Inducida por Sustancias y Drogas/patología , Fructosa/metabolismo , Gluconeogénesis/efectos de los fármacos , Glucógeno/metabolismo , Interacciones Hidrofóbicas e Hidrofílicas , Técnicas In Vitro , Cinética , Ácido Láctico/metabolismo , Membrana Dobles de Lípidos , Hígado/metabolismo , Hígado/patología , Masculino , Lípidos de la Membrana/química , Lípidos de la Membrana/metabolismo , Mitocondrias Hepáticas/efectos de los fármacos , Mitocondrias Hepáticas/metabolismo , Modelos Biológicos , Simulación de Dinámica Molecular , Fosforilación Oxidativa/efectos de los fármacos , Plaguicidas/química , Ratas Wistar , Medición de Riesgo , Urea/metabolismoRESUMEN
Many imidazole (IMZ) derivatives of pharmaceutical interest, which are potentially catalytic in dephosphorylation reactions, are soluble solely in mixtures of water and organic solvent. In order to understand these poorly explored reactions and properly compare them, a thorough study related to solvent effects for the analogous spontaneous reaction and with common IMZ derivatives is necessary, which is lacking in the literature. Herein, we report a quantitative solvent effect analysis in DMSO/water mixtures for (i) the hydrolysis reaction of diethyl 2,4-dinitrophenylphosphate (DEDNPP) and (ii) the nucleophilic reaction of IMZ and 1-methylimidazole (MEI) with DEDNPP. The solvent effect was fitted satisfactorily with multiple regression analysis, correlating the obtained second-order rate constants with solvent parameters such as acidity, basicity, and polarity/polarizability from Catalán's scale. The contribution of these parameters can be taken into account to elucidate the reactivity in these media. Interestingly, IMZ is more reactive than MEI in DMSO, compared to water alone, which is attributed to the availability of hydrogen-bond formation. Nuclear magnetic resonance spectroscopy ((1)H, (13)C, and (31)P), mass spectrometry, thermodynamic analysis, and density functional theory calculations were carried out to corroborate the proposed nucleophilic mechanism.
Asunto(s)
2,4-Dinitrofenol/análogos & derivados , Dimetilsulfóxido/química , Imidazoles/química , Organofosfatos/química , Solventes/química , Agua/química , 2,4-Dinitrofenol/química , Catálisis , Ésteres , Cinética , Espectroscopía de Resonancia Magnética , Fosfatos/químicaRESUMEN
Electrochemical oxidation (ECOx) of 1-hydroxy-2,4-dinitrobenzene (or 2,4-dinitrophenol: 2,4-DNP) in aqueous solutions by electrolysis under galvanostatic control was studied at Pb/PbO2, Ti/SnO2, Ti/IrxRuySnO2 and Si/BDD anodes as a function of current density applied. Oxidative degradation of 2,4-DNP has clearly shown that electrode material and the current density applied were important parameters to optimize the oxidation process. It was observed that 2,4-DNP was oxidized at few substrates to CO2 with different results, obtaining good removal efficiencies at Pb/PbO2, Ti/SnO2 and Si/BDD anodes. Trends in degradation way depend on the production of hydroxyl radicals (OH) on these anodic materials, as confirmed in this study. Furthermore, HPLC results suggested that two kinds of intermediates were generated, polyhydroxylated intermediates and carboxylic acids. The formation of these polyhydroxylated intermediates seems to be associated with the denitration step and substitution by OH radicals on aromatic rings, this being the first proposed step in the reaction mechanism. These compounds were successively oxidized, followed by the opening of aromatic rings and the formation of a series of carboxylic acids which were at the end oxidized into CO2 and H2O. On the basis of these information, a reaction scheme was proposed for each type of anode used for 2,4-D oxidation.
Asunto(s)
2,4-Dinitrofenol/química , Boro/química , Diamante/química , Metales Pesados/química , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Electroquímica , Electrodos , Oxidación-Reducción , Óxidos/química , SolucionesRESUMEN
2,4-Dinitrophenol (DNP) is a neuroprotective compound previously shown to promote neuronal differentiation in a neuroblastoma cell line and neurite outgrowth in primary neurons. Here, we tested the hypothesis that DNP could induce neurogenesis in embryonic stem cells (ESCs). Murine ESCs, grown as embryoid bodies (EBs), were exposed to 20 µM DNP (or vehicle) for 4 days. Significant increases in the proportion of nestin- and ß-tubulin III-positive cells were detected after EB exposure to DNP, accompanied by enhanced glial fibrillary acidic protein (GFAP), phosphorylated extracellular signal-regulated kinase (p-ERK) and ATP-linked oxygen consumption, thought to mediate DNP-induced neural differentiation. DNP further protected ESCs from cell death, as indicated by reduced caspase-3 positive cells, and increased proliferation. Cell migration from EBs was significantly higher in DNP-treated EBs, and migrating cells were positive for nestin, ß-tubulin III and MAP2, similar to that observed with retinoic acid (RA)-treated EBs. Compared to RA, however, DNP exerted a marked neuritogenic effect on differentiating ESCs, increasing the average length and number of neurites per cell. Results establish that DNP induces neural differentiation of ESCs, accompanied by cell proliferation, migration and neuritogenesis, suggesting that DNP may be a novel tool to induce neurogenesis in embryonic stem cells.
Asunto(s)
2,4-Dinitrofenol/farmacología , Cuerpos Embrioides/efectos de los fármacos , Células Madre Embrionarias/efectos de los fármacos , Neurogénesis/efectos de los fármacos , Neuronas/citología , 2,4-Dinitrofenol/química , Animales , Diferenciación Celular , Línea Celular , Movimiento Celular , Proliferación Celular , Cuerpos Embrioides/citología , Cuerpos Embrioides/metabolismo , Células Madre Embrionarias/citología , Proteína Ácida Fibrilar de la Glía , Ratones , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteína Quinasa 3 Activada por Mitógenos/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Nestina/metabolismo , Neuronas/metabolismo , Consumo de Oxígeno , Tretinoina/farmacología , Tubulina (Proteína)/metabolismoRESUMEN
This work presents a detailed kinetic and mechanistic study of biologically interesting dephosphorylation reactions involving the exceptionally reactive nucleophilic group, hydroxamate. We compare results for hydroxamate groups anchored on the simple molecular backbone of benzohydroxamate (BHA) and on the more complex structure of the widely used drug, deferoxamine (DFO). BHA shows extraordinary reactivity toward the triester diethyl 2,4-dinitrophenyl phosphate (DEDNPP) and the diester ethyl 2,4-dinitrophenyl phosphate (EDNPP) but reacts very slowly with the monoester 2,4-dinitrophenyl phosphate (DNPP). Nucleophilic attack on phosphorus is confirmed by the detection of the phosphorylated intermediates formed. These undergo Lossen-type rearrangements, resulting in the decomposition of the nucleophile. DFO, which is used therapeutically for the treatment of acute iron intoxication, carries three hydroxamate groups and shows correspondingly high nucleophilic activity toward both triester DEDNPP and diester EDNPP. This result suggests a potential use for DFO in cases of acute poisoning with phosphorus pesticides.
Asunto(s)
2,4-Dinitrofenol/análogos & derivados , Deferoxamina/química , Ácidos Hidroxámicos/química , Organofosfatos/química , Compuestos Organoplatinos/química , Plaguicidas/química , Fosfatos/química , 2,4-Dinitrofenol/química , Hidrólisis , Cinética , Espectroscopía de Resonancia Magnética , Estructura Molecular , Compuestos Organoplatinos/envenenamiento , Plaguicidas/envenenamiento , FosforilaciónRESUMEN
We report a detailed kinetic and mechanistic study of the reaction of a widely used therapeutic agent, deferoxamine (DFO), which contains three nucleophilic hydroxamate groups, with the model phosphate diester bis-2,4-dinitrophenylphosphate BDNPP. We clarify the mechanism by detecting important phosphorylated intermediates in the model reaction and show that the mechanism can be extended to the reaction with DNA. The effectiveness of DFO in cleaving DNA was examined over a range of pH in the absence and presence of a biologically available metal (Zn(2+)). The results inform and complement ongoing studies involving DFO, which can act as a powerful nucleophile toward DNA and other targets susceptible to nucleophilic attack.
Asunto(s)
2,4-Dinitrofenol/análogos & derivados , Antineoplásicos/química , Deferoxamina/química , Quelantes del Hierro/química , Organofosfatos/química , 2,4-Dinitrofenol/química , ADN/metabolismo , División del ADN , Concentración de Iones de Hidrógeno , Hidrólisis , Ácidos Hidroxámicos/química , Cinética , Espectrometría de Masa por Ionización de Electrospray , Espectrofotometría , Zinc/químicaRESUMEN
The natural alkaloid quinine (QN) was immobilized on porous silica particles, and part of the material was subsequently endcapped with n-hexyl hydrocarbon chains. Two synthetic strategies for silanization of the support were first compared. These columns were thoroughly evaluated in order to study the influence of endcapping in the enantiorecognition features. Enantioseparations of twenty N-derivatized 2,4-dinitrophenyl α-amino acids (DNP-amino acids) were studied by changing mobile phase pH, buffer concentration, type of organic solvent in the mobile phase, and column temperature. Maximum retention factors were observed at pH ≈6, at this intermediate pH the tertiary amine of the quinine is protonated to a high degree and therefore available for strong electrostatic interactions with unprotonated anionic DNP-amino acids. The enantioselectivity factors, however, increased as the pH did in the range between 5 and 7. The increase in ionic strength had influence on retention, but not on enantioselectivity, allowing the use of this variable for optimization of retention factors. Finally, the thermodynamic transfer parameters of the enantiomers from the mobile to both CSPs (with and without endcapping, QN-CSP(EC) and QN-CSP, respectively) were estimated from van't Hoff plots within the range of 10-40 °C. Thus, the differences in the transfer enthalpy, Δ(ΔH°), and transfer entropy, Δ(ΔS°), enabled an investigation of the origin of the differences in interaction energies.
Asunto(s)
2,4-Dinitrofenol/química , Aminoácidos/aislamiento & purificación , Cromatografía por Intercambio Iónico/métodos , Quinina/química , Acetonitrilos/química , Aminoácidos/química , Concentración de Iones de Hidrógeno , Metanol/química , Concentración Osmolar , Dióxido de Silicio/química , Estereoisomerismo , Temperatura , TermodinámicaRESUMEN
The reaction between the benzohydroxamate anion (BHO(-)) and bis(2,4-dinitrophenyl)phosphate (BDNPP) has been examined kinetically, and the products were characterized by mass and NMR spectroscopy. The nucleophilic attack of BHO(-) follows two reaction paths: (i) at phosphorus, giving an unstable intermediate that undergoes a Lossen rearrangement to phenyl isocyanate, aniline, diphenylurea, and O-phenylcarbamyl benzohydroxamate; and (ii) on the aromatic carbon, giving an intermediate that was detected but slowly decomposes to aniline and 2,4-dinitrophenol. Thus, the benzohydroxamate anion can be considered a self-destructive molecular scissor since it reacts and loses its nucleophilic ability.
Asunto(s)
2,4-Dinitrofenol/química , Benceno , Ácidos Hidroxámicos/química , Fosfatos/química , Aniones , Cinética , Espectroscopía de Resonancia Magnética , Estructura MolecularRESUMEN
Access to different intermediates that follow ATP cleavage in the catalytic cycle of skeletal muscle actomyosin is a major goal of studies that aim toward an understanding of chemomechanical coupling in muscle contraction. 2,4-Dinitrophenol (DNP, 10(-2) M) inhibits muscle contraction, even though it accelerates the ATPase activity of isolated myosin. Here we used myosin subfragment 1 (S1), acto-S1 and mammalian skinned fibers to investigate the action of DNP in the presence of actin. DNP increases acto-S1 affinity and at the same time reduces the maximum rate of turnover as [actin]-->infinity. In skinned fibers, isometric force is reduced to the same extent (K0.5 approximately equal to 6 mM). Although actin activates Pi release from S1 at all DNP concentrations tested, the combination of enhanced S1 activity and reduced acto-S1 activity leads to a reduction in the ratio of these two rates by a factor of 30 at the highest DNP concentration tested. This effect is seen at low as well as at high actin concentrations and is less pronounced with the analog meta-nitrophenol (MNP), which does not inhibit the acto-S1 ATPase. Arrhenius plots for acto-S1 are parallel and linear between 5 and 30 degrees C, indicating no abrupt shifts in rate-limiting step with either DNP or MNP. Analysis of the reduction in isometric force with increasing Pi concentrations suggests that DNP and MNP stabilize weakly bound cross-bridges (AM.ADP.Pi). In addition, MNP (10(-2) M) increases the apparent affinity for Pi.
Asunto(s)
2,4-Dinitrofenol/química , Actomiosina/química , Adenosina Trifosfato/química , Actinas/química , Actomiosina/metabolismo , Animales , Relación Dosis-Respuesta a Droga , Hidrólisis , Cinética , Modelos Químicos , Contracción Muscular , Músculo Esquelético/citología , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/metabolismo , Miosinas/química , Nitrofenoles/farmacología , Unión Proteica , Conejos , TemperaturaRESUMEN
Photolysis of nitroaromatic compounds in aqueous solution is a very slow and inefficient process. As already observed for a variety of organic pollutants, considerably faster degradation rates of nitrobenzene (NBE), 1-chloro-2,4-dinitrobenzene (CDNB), 2,4-dinitrophenol (DNP), and 4-nitrophenol (PNP) could be achieved, when the oxidative degradation of these compounds was initiated by hydroxyl radicals produced by UV-C photolysis of H2O2. Analysis of intermediate products formed during irradiation by HPLC and IC showed that cleavage of the aromatic ring should occur at an early stage of the oxidation process and that organic nitrogen was almost completely converted to nitrate. The optimal initial concentration of hydrogen peroxide ([H2O2]OPT) leading to the fastest oxidation rate, which depends on the initial substrate concentration ([S]0), could be evaluated using a simplified expression based on the main reactions involved in the first stages of the degradation process. Using only a minimum of kinetic and analytical information, this expression shows that the ratio R(OPT) (= [H2O2]OPT/[S]0) is related to the bimolecular rate constants for the reactions of hydroxyl radicals with substrate (kS) and H2O2 (kHP) and to the corresponding molar absorption coefficients (epsilonS, epsilonHP). Competition experiments between selected pairs of the substrates showed that their relative reactivity toward hydroxyl radicals could be correctly predicted using the same simplified approach. The results of our investigations as well as literature data support the general validity of the proposed procedure for optimizing oxidation rates of the UV/H2O2 process.