The metabolic activation of pentachlorophenol to chloranil as a potent inhibitor of human and rat placental 3ß-hydroxysteroid dehydrogenases.

Pentachlorophenol (PCP) is a widely used pesticide. However, whether PCP and its metabolite chloranil have endocrine-disrupting effects by inhibiting placental 3ß-hydroxysteroid dehydrogenase 1 (3ß-HSD1) remains unclear. The study used in vitro assays with human and rat placental microsomes to measure 3ß-HSD activity as well as human JAr cells to evaluate progesterone production. The results showed that PCP exhibited moderate inhibition of human 3ß-HSD1, with an IC50 value of 29.83 µM and displayed mixed inhibition in terms of mode of action. Conversely, chloranil proved to be a potent inhibitor, demonstrating an IC50 value of 147 nM, and displaying a mixed mode of action. PCP significantly decreased progesterone production by JAr cells at 50 µM, while chloranil markedly reduced progesterone production at ≥1 µM. Interestingly, PCP and chloranil moderately inhibited rat placental homolog 3ß-HSD4, with IC50 values of 27.94 and 23.42 µM, respectively. Dithiothreitol (DTT) alone significantly increased human 3ß-HSD1 activity. Chloranil not PCP mediated inhibition of human 3ß-HSD1 activity was completely reversed by DTT and that of rat 3ß-HSD4 was partially reversed by DTT. Docking analysis revealed that both PCP and chloranil can bind to the catalytic domain of 3ß-HSDs. The difference in the amino acid residue Cys83 in human 3ß-HSD1 may explain why chloranil is a potent inhibitor through its interaction with the cysteine residue of human 3ß-HSD1. In conclusion, PCP is metabolically activated to chloranil as a potent inhibitor of human 3ß-HSD1.

Charge transfer complex-based spectrophotometric analysis of famotidine in pure and pharmaceutical dosage forms.

A straightforward and efficient spectrum technique was created using Ortho-chloranil as the electron acceptor (-acceptor) in a charge transfer (CT) complex formation reaction to determine the concentration of famotidine (FMD) in solutions. Compared to the double-distilled blank solution, the reaction result detected a definite violet colour at a maximum absorption wavelength of 546 nm, For concentrations range 2-28 µg/ml, the technique demonstrated excellent compliance with Beer-Law and Lambert's, as evidenced by its molar absorptivity of 2159.648 L mol-1 cm-1. Lower detection limits of 0.3024 µg/ml and 1.471 µg/ml, respectively, were discovered. The complexes of famotidine and Ortho-chloranil were found to have a 2:1 stoichiometry. Additionally, the suggested approach effectively estimated famotidine concentrations in pharmaceutical formulations, particularly in tablet form.

Dynamic control of pentachlorophenol photodegradation process using P25/PDA/BiOBr through regulation of photo-induced active substances and chemiluminescence.

Photodegradation is a new approach for the removal of pentachlorophenol (PCP). Photooxidation degradation (using hydroxyl radicals) exhibits better performance to remove PCP than photoreduction degradation, but the former will lead to an increase in the production of toxic by-products such as tetrachloro-1,4-benzoquinone (TCBQ). Thus, a new strategy is required to enhance PCP photodegradation and simultaneously inhibit toxic intermediates production. Herein, TiO2 (P25)/polydopamine (PDA)/BiOBr was synthesized and used to photodegrade PCP. Based on the relative position of the CB and VB of P25 and BiOBr, and PDA as an electron transfer mediator, a high number of holes, electrons, and superoxide anions were produced instead of hydroxyl radicals. The photocatalytic activity of P25/PDA/BiOBr exhibited the best performance among as-prepared samples, reaching a k(pcp) value of 0.4 min-1 (20 µM PCP) under UV light irradiation within 10 min. According to chemiluminescence and acute toxicity assays, relative to P25, the toxic intermediates of TCBQ and trichlorohydroxy-1,4-benzoquinone (OH-TrCBQ) generation was greatly reduced over P25/PDA/BiOBr, with a lack of toxic product generation during PCP photodegradation process. These findings provide an alternative strategy to achieve greener and more efficient organic pollutant photodegradation.

Role of tetrachloro-1,4-benzoquinone reductase in phenylalanine hydroxylation system and pentachlorophenol degradation in Bacillus cereus AOA-CPS1.

This study reports a ≅12.5 kDa protein tetrachloro-1,4-benzoquinone reductase (CpsD) from Bacillus cereus strain AOA-CPS1 (BcAOA). CpsD is purified to homogeneity with a total yield of 35% and specific activity of 160 U·mg-1 of protein. CpsD showed optimal activity at pH 7.5 and 40 °C. The enzyme was found to be functionally stable between pH 7.0-7.5 and temperature between 30 °C and 35 °C. CpsD activity was enhanced by Fe2+ and inhibited by sodium azide and SDS. CpsD followed Michaelis-Menten kinetic exhibiting an apparent vmax, Km, kcat and kcat/Km values of 0.071 µmol·s-1, 94 µmol, 0.029 s-1 and 3.13 × 10-4 s-1·µmol-1, respectively, for substrate tetrachloro-1,4-benzoquinone. The bioinformatics analysis indicated that CpsD belongs to the PCD/DCoH superfamily, with specific conserved protein domains of pterin-4α-carbinolamine  dehydratase (PCD). This study proposed that CpsD catalysed the reduction of tetrachloro-1,4-benzoquinone to tetrachloro-p-hydroquinone and released the products found in phenylalanine hydroxylation system (PheOHS) via a Ping-Pong or atypical ternary mechanism; and regulate expression of phenylalanine 4-monooxygenase by blocking reverse flux in BcAOA PheOHS using a probable Yin-Yang mechanism. The study also concluded that CpsD may play a catalytic and regulatory role in BcAOA PheOHS and pentachlorophenol degradation pathway.

Spectroscopic investigation of π-acceptors in the determination and photoinduced degradation of Sulfacetamide.

The presence of expired and unused Sulfacetamide (SA) drug in water led to a global need for the development of effective advanced method for the quantitative analysis and for minimizing its occurrence in the nature. To find new effective photochemical decomposition method close to that obtained by the well-known Fenton reaction, the photodegradation of SA was investigated in presence of dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and/or other common additives at two different wavelengths (365 and 256 nm). The role of DDQ in the degradation process of SA was evaluated in comparison to the other investigated π-acceptor systems (Chloranilic acid (CHL) and Picric acid (PA)). While the photodegradation process of SA was hardly to proceed in the absence of a catalyst and/or additive, addition of DDQ and NaNO2 to the solution of SA induced decomposition of about 94% of SA within 25 min upon the exposure to light source at 256 nm. On the other hand, SA was quantitatively analyzed by recording the absorbance of its charge transfer (CT) products with DDQ, CHL and PA at a certain wavelength. CHL is preferred with concentrated samples of SA, while PA is recommended for diluted samples of SA. SA â†’ DDQ has a widely range of stability over the pH range of 4.5-12.0. While SA â†’ CHL is stable only in the acidic medium (pH = 4.8-5.6), SA â†’ PA is steady in the basic medium (pH = 7.5-11.0). The nature of the DDQ CT complex was investigated in the solid state. The electronic structures of the complexes were studied by calculating the time dependent density functional theory (TDDFT) spectra.

An unusual double radical homolysis mechanism for the unexpected activation of the aldoxime nerve-agent antidotes by polyhalogenated quinoid carcinogens under normal physiological conditions.

We have recently shown that the pyridinium aldoximes, best-known as therapeutic antidotes for chemical warfare nerve-agents, could markedly detoxify the carcinogenic tetrachloro-1,4-benzoquinone (TCBQ) via an unusual double Beckmann fragmentation mechanism. However, it is still not clear why pralidoxime (2-PAM) cannot provide full protection against TCBQ-induced biological damages even when 2-PAM was in excess. Here we show, unexpectedly, that TCBQ can also activate pralidoxime to generate a reactive iminyl radical intermediate in two-consecutive steps, which was detected and unequivocally characterized by the complementary application of ESR spin-trapping, HPLC/MS and nitrogen-15 isotope-labeling studies. The same iminyl radical was observed when TCBQ was substituted by other halogenated quinones. The end product of iminyl radical was isolated and identified as its corresponding reactive and toxic aldehyde. Based on these data, we proposed that the reaction of 2-PAM and TCBQ might be through the following two competing pathways: a nucleophilic attack of 2-PAM on TCBQ forms an unstable transient intermediate, which can decompose not only heterolytically to form 2-CMP via double Beckmann fragmentation, but also homolytically leading to the formation of a reactive iminyl radical in double-steps, which then via H abstraction and further hydrolyzation to form its corresponding more toxic aldehyde. Analogous radical homolysis mechanism was observed with other halogenated quinones and pyridinium aldoximes. This study represents the first detection and identification of reactive iminyl radical intermediates produced under normal physiological conditions, which provides direct experimental evidence to explain only the partial protection by 2-PAM against TCBQ-induced biological damages, and also the potential side-toxic effects induced by 2-PAM and other pyridinium aldoxime nerve-agent antidotes.

Photosystem I with benzoquinone analogues incorporated into the A1 binding site.

Time-resolved FTIR difference spectroscopy has been used to study photosystem I (PSI) particles with three different benzoquinones [plastoquinone-9 (PQ), 2,6-dimethyl-1,4-benzoquinone (DMBQ), 2,3,5,6-tetrachloro-1,4-benzoquinone (Cl4BQ)] incorporated into the A1 binding site. If PSI samples are cooled in the dark to 77 K, the incorporated benzoquinones are shown to be functional, allowing the production of time-resolved (P700+A1--P700A1) FTIR difference spectra. If samples are subjected to repetitive flash illumination at room temperature prior to cooling, however, the time-resolved FTIR difference spectra at 77 K display contributions typical of the P700 triplet state (3P700), indicating a loss of functionality of the incorporated benzoquinones, that occurs because of double protonation of the incorporated benzoquinones. The benzoquinone protonation mechanism likely involves nearby water molecules but does not involve the terminal iron-sulfur clusters FA and FB. These results and conclusions resolve discrepancies between results from previous low-temperature FTIR and EPR studies on similar PSI samples with PQ incorporated.

Shift current photovoltaic effect in a ferroelectric charge-transfer complex.

Shift current is a steady-state photocurrent generated in non-centrosymmetric single crystals and has been considered to be one of the major origins of the bulk photovoltaic effect. The mechanism of this effect is the transfer of photogenerated charges by the shift of the wave functions, and its amplitude is closely related to the polarization of the electronic origin. Here, we report the photovoltaic effect in an organic molecular crystal tetrathiafulvalene-p-chloranil with a large ferroelectric polarization mostly induced by the intermolecular charge transfer. We observe a fairly large zero-bias photocurrent with visible-light irradiation and switching of the current direction by the reversal of the polarization. Furthermore, we reveal that the travel distance of photocarriers exceeds 200 µm. These results unveil distinct features of the shift current and the potential application of ferroelectric organic molecular compounds for novel optoelectric devices.The bulk photovoltaics refers to an effect whereby electrons move directionally in non-centrosymmetric crystals upon light radiation. Here, Nakamura et al. observe this effect in a ferroelectric organic charge-transfer complex, which shows large diffusion distance of photogenerated electrons over 200 µm.

The acute exposure of tetrachloro-p-benzoquinone (a.k.a. chloranil) triggers inflammation and neurological dysfunction via Toll-like receptor 4 signaling: The protective role of melatonin preconditioning.

This study is aimed to investigate the inflammation and neurological dysfunction induced by tetrachloro-p-benzoquinone (TCBQ) through Toll-like receptor 4 (TLR4) signaling. We also investigated the protective role of melatonin as an antioxidant and anti-inflammatory agent. In vitro model was established by rat pheochromocytoma PC12 cells, meanwhile, TLR4 wild-type (C57BL/6) and knockout mice (C57BL/10ScNJ TLR4-/-) were used as in vivo model. In vitro study showed TCBQ exposure enhanced the expression of TLR4, myeloid differentiation factor 88 (MyD88) at both transcriptional and post-transcriptional levels. By contrast, melatonin decreased TLR4 and MyD88 expressions. Moreover, our result indicated that melatonin disrupted the formation of TLR4/MyD88/MD2/CD14 complex. In addition, melatonin terminated TCBQ-mediated phosphorylation of c-Jun N-terminal kinase (JNK), p38, and extracellular regulated protein kinase (ERK) signaling and hampered its downstream pro-inflammatory cytokine releases. In vivo result also indicated TLR4 deficiency partially protected against TCBQ-induced morphological and neuropathological changes in mice brain, suggested the role of TLR4. In conclusion, melatonin modulates TCBQ-mediated inflammatory genes through TLR4/MyD88-dependent signaling pathway. Our current study, to the best of our knowledge, is the first time show melatonin not only disrupt the binding of TLR4 and MyD88, but also restricted the formation of TLR4/MD2/CD14 complex, suggesting that melatonin supplementary may represent a valuable therapeutic strategy for inflammatory neurological dysfunction.

Synthetic approaches towards the multi target drug spironolactone and its potent analogues/derivatives.

Spironolactone is a well-known multi-target drug and is specifically used for the treatment of high blood pressure and heart failure. It is also used for the treatment of edema, cirrhosis of the liver, malignant, pediatric, nephrosis and primary hyperaldosteronism. Spironolactone in association with thiazide diuretics treats hypertension and in association with furosemide treats bronchopulmonary dyspepsia. The therapeutic mechanism of action of spironolactone involves binding to intracellular mineralocorticoids receptors (MRs) in kidney epithelial cells, thereby inhibiting the binding of aldosterone. Since its first synthesis in 1957 there are several synthetic approaches have been reported throughout the years, Synthetic community has devoted efforts to improve the synthesis of spironolactone and to synthesize its analogues and derivatives. This review aims to provide comprehensive insight for the synthetic endeavors devoted towards the synthesis of a versatile drug spironolactone and its analogues/derivatives.

Tetrachloro-1,4-benzoquinone induces apoptosis of mouse embryonic stem cells.

Pentachlorophenol (PCP) is a widespread, persistent environmental contaminant, and it is enzymatically activated to form a reactive metabolite, tetrachloro-1,4-benzoquinone (TCBQ). To our knowledge, there is no information about TCBQ toxicity on embryonic stem cells. Here, we demonstrated that TCBQ induced significantly apoptosis of mouse embryonic stem cells in a concentration-dependent manner. We also showed that TCBQ elevated genomic 5-hydroxymethylcytosine (5hmC) by affecting ten-eleven translocation (Tet) dioxygenases in mouse embryonic stem cells. We further investigated whether Tet dioxygenases were implicated in TCBQ-induced apoptosis. By depleting all three dioxygenases (Tet1-3), we found that Tet dioxygenases slightly inhibited both early and late apoptosis induced by TCBQ at a low concentration (30µmol/L). Meanwhile, treated by TCBQ at higher concentrations (40 and 50µmol/L), the total percentage of apoptotic cells was not affected by Tet dioxygenases. However, Tet dioxygenases tended to arrest mouse ES cells to be at early apoptotic stage and to reduce the cells to enter later apoptotic stage. These results indicate that Tet dioxygenases play a role in shaping TCBQ-induced apoptosis in mouse embryonic stem cells. Our study provides new insights into the toxicology of PCP and its reactive metabolite TCBQ.

An Exceptionally Facile Two-Step Structural Isomerization and Detoxication via a Water-Assisted Double Lossen Rearrangement.

N-hydroxyphthalimide (NHPI), which is best known as an organocatalyst for efficient C-H activation, has been found to be oxidized by quinoid compounds to its corresponding catalytically active nitroxide-radical. Here, we found that NHPI can be isomerized into isatoic anhydride by an unusually facile two-step method using tetrachloro-1,4-benzoquinone (TCBQ, p-chloranil), accompanied by a two-step hydrolytic dechlorination of highly toxic TCBQ into the much less toxic dihydroxylation product, 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid). Interestingly, through the complementary application of oxygen-18 isotope-labeling, HPLC combined with electrospray ionization quadrupole time-of-flight and high resolution Fourier transform ion cyclotron resonance mass spectrometric studies, we determined that water was the source and origin of oxygen for isatoic anhydride. Based on these data, we proposed that nucleophilic attack with a subsequent water-assisted Lossen rearrangement coupled with rapid intramolecular addition and cyclization in two consecutive steps was responsible for this unusual structural isomerization of NHPI and concurrent hydroxylation/detoxication of TCBQ. This is the first report of an exceptionally facile double-isomerization of NHPI via an unprecedented water-assisted double-Lossen rearrangement under normal physiological conditions. Our findings may have broad implications for future research on hydroxamic acids and polyhalogenated quinoid carcinogens, two important classes of compounds of major chemical and biological interest.

Charge transfer interaction of organic p-acceptors with the anti-hyperuricemic drug allopurinol: Insights from IR, Raman, 1H NMR and 13C NMR spectroscopies.

The topic of charge-transfer (CT) complexation of vital drugs has attracted considerable attention in recent years owing to their significant physical and chemical properties. In this study, CT complexes derived from the reaction of the anti-hyperuricemic drug allopurinol (Allop) with organic p-acceptors [(picric acid (PA), dichlorodicyanobenzoquinone (DDQ) and chloranil (CHL)] were prepared, isolated and characterized by a range of physicochemical methods, such as IR, Raman, 1H NMR and 13C NMR spectroscopy. The stoichiometry of the complexes was verified by elemental analysis. The results show that all complexes that were formed were based on a 1:1 stoichiometric ratio. This study suggests that the complexation of Allop with either the DDQ or CHL acceptor leads to a direct p®p* transition, whereas the molecules of Allop and PA are linked by intermolecular hydrogen- bonding interactions.

Spectral, thermal and kinetic studies of charge-transfer complexes formed between the highly effective antibiotic drug metronidazole and two types of acceptors: σ- and π-acceptors.

Understanding the interaction between drugs and small inorganic or organic molecules is critical in being able to interpret the drug-receptor interactions and acting mechanism of these drugs. A combined solution and solid state study was performed to describe the complexation chemistry of drug metronidazole (MZ) which has a broad-spectrum antibacterial activity with two types of acceptors. The acceptors include, σ-acceptor (i.e., iodine) and π-acceptors (i.e., dichlorodicyanobenzoquinone (DDQ), chloranil (CHL) and picric acid (PA)). The molecular structure, spectroscopic characteristics, the binding modes as well as the thermal stability were deduced from IR, UV-vis, (1)H NMR and thermal studies. The binding ratio of complexation (MZ: acceptor) was determined to be 1:2 for the iodine acceptor and 1:1 for the DDQ, CHL or PA acceptor, according to the CHN elemental analyses and spectrophotometric titrations. It has been found that the complexation with CHL and PA acceptors increases the values of enthalpy and entropy, while the complexation with DDQ and iodine acceptors decreases the values of these parameters compared with the free MZ donor.

Compatible validated spectrofluorimetric and spectrophotometric methods for determination of vildagliptin and saxagliptin by factorial design experiments.

Simple, selective and reproducible spectrofluorimetric and spectrophotometric methods have been developed for the determination of vildagliptin and saxagliptin in bulk and their pharmaceutical dosage forms. The first proposed spectrofluorimetric method is based on the dansylation reaction of the amino group of vildagliptin with dansyl chloride to form a highly fluorescent product. The formed product was measured spectrofluorimetrically at 455 nm after excitation at 345 nm. Beer's law was obeyed in a concentration range of 100-600 µg ml(-1). The second proposed spectrophotometric method is based on the charge transfer complex of saxagliptin with tetrachloro-1,4-benzoquinone (p-chloranil). The formed charge transfer complex was measured spectrophotometrically at 530 nm. Beer's law was obeyed in a concentration range of 100-850 µg ml(-1). The third proposed spectrophotometric method is based on the condensation reaction of the primary amino group of saxagliptin with formaldehyde and acetyl acetone to form a yellow colored product known as Hantzsch reaction, measured at 342.5 nm. Beer's law was obeyed in a concentration range of 50-300 µg ml(-1). All the variables were studied to optimize the reactions' conditions using factorial design. The developed methods were validated and proved to be specific and accurate for quality control of vildagliptin and saxagliptin in their pharmaceutical dosage forms.

Halogen vs hydrogen bonding in thiazoline-2-thione stabilization with σ- and π-electron acceptors adducts: theoretical and experimental study.

Molecular charge-transfer complexes (CT) between thiazoline-2-thione (THZ) and different σ- (I2) and π-acceptors (Tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), and 2,3,5,6-tetrachloro-1,4-benzoquinone (CHL)) were investigated. UV-Vis absorption spectroscopy and theoretical calculations using both MP2/aug-cc-pVDZ-PP and B3LYP/6-311++G(d,p) level of theory were corroborated to study the nature of the stabilizing forces for THZ-I2, THZ-DDQ, THZ-TCNE, and THZ-CHL. Halogen bonding (XB) was the stabilizing attractive force in THZ-I2 and THZ-CHL whereas; hydrogen bonding (HB) was dominated in both THZ-TCNE, and THZ-DDQ complexes. Formation constant (K), extinction coefficient (ɛ), thermodynamic parameters such as enthalpy change (ΔH), entropy (ΔS), and Gibbs free energy (ΔG) were measured in different solvents.

Charge transfer in the electron donor-acceptor complexes of a meso-phenol BODIPY dye with chloranils and fullerenes.

UV-Vis spectral investigations of electron donor-acceptor complexes of laser dye 2,6-Diethyl-4,4-difluoro-1,3,5,7-tetramethyl-8-(4'-hydroxyphenyl)-4-bora-3a,4a-diaza-s-indecene (1c) with chloranils and fullerenes are reported in toluene medium. Well defined charge transfer (CT) absorption bands have been located in the visible region. Oscillator strengths, transition dipole and resonance energies of the CT complexes have been estimated. Vertical ionization potential of 1c has been determined utilizing Mulliken's equation. A possible mechanism for the interaction between electronic subsystems of chloranils, [60]- and [70]fullerenes with three different BODIPY dyes (1a, 1b and 1c shown in Fig. 1) have been discussed in comparing the parameters like degree of charge transfer and binding constant in nonpolar toluene. Comparison of 1c complexes is done with DFT/B3LYP/6-31G optimized gas phase geometries.

Tetrachlorobenzoquinone induces acute liver injury, up-regulates HO-1 and NQO1 expression in mice model: the protective role of chlorogenic acid.

Tetrachlorobenzoquinone (TCBQ) is an active metabolite of pentachlorophenol (PCP). Although PCP has been investigated extensively, there are only a few reports describing the toxicity effect of TCBQ, and no report regarding TCBQ-induced liver injury in vivo. In the current study, we aimed to examine the acute hepatic toxicity of TCBQ in the mice model. Chlorogenic acid (CGA) exhibits promising antioxidant activity in the past studies, thus, the second aim of this study was to evaluate the protective effect of CGA on TCBQ-induced liver injury. Our results indicated TCBQ-intoxication caused marked liver cell necrosis and inflammation but not apoptosis, and this damage was alleviated by CGA treatment. Meantime, TCBQ-intoxication enhanced serum ALT, AST activities, TBIL content, hepatic oxidative stress and lipid peroxidation, decreased GSH content and inhibited the activities of antioxidant enzymes. Western blot and immunohistochemical analysis showed that TCBQ marked up-regulated HO-1 and NQO1 expression. On the other hand, pretreatment of CGA reduced TCBQ-induced liver damage remarkably. Taking together, these results revealed that TCBQ has strong hepatic toxic effect, and at least a part of this effect is initiated by free radical and relieved with CGA administration.