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In this study, the effects of physicochemical and biochemical digestion conditions on β-arbutin stability and bioaccessibility were investigated. β-Arbutin, at doses that correspond to its natural occurrence in plant materials (i.e., 1–100 mg), was subjected to gastric and intestinal electrolyte treatments (application of physicochemical factors) or the whole digestion process (application of physicochemical and biochemical factors). Its content in in vitro bioaccessible fractions was determined using high-performance liquid chromatography (HPLC), and percentage bioaccessibility was calculated. The study shows very high stability and bioaccessibility of β-arbutin in a wide range of applied concentrations. Especially at doses ≥7.5 mg, bioaccessibility was close to 100% regardless of the stage of digestion and the type of treatment (electrolyte treatment or the whole digestion process). The assessment of phytochemicals in terms of their stability and interactions with the digestion environment can help in the future evaluation of their applicability for therapeutic purposes. The high bioaccessibility of β-arbutin within its multifunctional biological activity makes it a promising substance for phytomedicinal applications. [ABSTRACT FROM AUTHOR]

Background: Melasma is a challenging, acquired hyperpigmentary disorder. The gold standard treatment is Kligman's formulation, which contains hydroquinone, tretinoin, and dexamethasone, but its long-term use is limited by the risk of exogenous ochronosis. Cysteamine, a tyrosinase inhibitor, reduces melanocyte activity and melanin production, showing strong depigmenting effects in patients resistant to Kligman's formulation. Nonetheless, clinical studies have yielded inconsistent efficacy results. This meta-analysis aimed to assess the efficacy of cysteamine in treating melasma and to identify potential factors that may impact its therapeutic outcomes. Methods: A systematic search of PubMed, Embase, Web of Science, and CENTRAL, from the earliest record until August 2024, was conducted. Randomized controlled trials and quasi-randomized design studies related to topical cysteamine on melasma patients were included. The primary outcome was MASI or mMASI assessment after treatments. The current meta-analysis was conducted with a random-effects model. Subgroup analyses and meta-regressions were performed based on baseline MASI, disease duration of melasma, patient age, and sample size of the included studies. Funnel plots and Duval and Tweedie's trim and fill method were adopted to assess the publication bias. Results: Eight studies were included for quantitative analysis. The analysis of MASI after topical cysteamine demonstrated a significant decrease compared to the placebo (p = 0.002). Compared to other melasma treatments, cysteamine did not show superior efficacy in mMASI (p = 0.277). The treatment efficacy of hydroquinone, modified Kligman's formula, and tranexamic acid mesotherapy for melasma was not statistically different when compared to cysteamine (p = 0.434). Further analyses showed no benefit when allowing extended cysteamine application time (p < 0.0001). The meta-regression revealed the efficacy of cysteamine decreased as the duration of melasma increased (coefficient = 0.38, p = 0.0001, R2 = 0.99). The funnel plot displayed some asymmetry. The trim and fill method suggested the adjusted effect size was 0.607 (95% CI = −0.720 to 1.935). Conclusions: Cysteamine exhibited efficacy in treating melasma patients; however, its depigmentation effect was comparable to hydroquinone-based regimens, tranexamic acid mesotherapy, and modified Kligman's formula. Using cysteamine in patients with a short duration of melasma may result in better efficacy. [ABSTRACT FROM AUTHOR]

Direct hydroxylation of aromatics and phenol processes using green oxidants plays an important role in the petrochemical industry. High selectivity towards hydroquinone is usually hard to achieve due to catechol formation and catalyst deactivation. Herein, we showed the recent studies devoted to selective phenol hydroxylation via oxidation using H2O2. This review summarizes progress that has been achieved in this area. Briefly, aromatic hydroxylation on heterogeneous catalysts, phenol hydroxylation on Ti-containing and supported catalysts, photocatalytic hydroxylation, and new approaches toward phenol hydroxylation have been reviewed. [ABSTRACT FROM AUTHOR]

Rapidly escalating energy demands have spurred a relentless quest for innovative materials and methodologies in energy storage technologies. Covalent organic frameworks (COFs) have emerged as promising candidates for energy storage applications owing to their customizable structure and inherent properties, including enduring porosity and expansive surface area. In this study, we introduce imine-based COF aerogels fashioned into flexible COF electrodes, employing redox electrolytes based on hydroquinone (HQ) dissolved in H2SO4 aqueous solution and 0.25 M TBAPF6 at concentration in acetonitrile. This strategic selection of electrolytes aims to augment capacitance and energy density when compared to non-redox electrolytes. Remarkably, our COF electrodes exhibit an outstanding areal capacitance of 843 mF cm−2 when utilizing HQ with 0.10 M H2SO4, operating at 1.3 mA cm−2, while maintaining approximately 100% capacity retention after 10,000 cycles. Notably, the capacitance of the 0.38 M HQ + 0.10 M H2SO4 is eight times greater than that achieved with organic electrolytes (111 mF cm−2). [ABSTRACT FROM AUTHOR]

The current energy scenario requires the use of alternatives for petrol-based products. In this context, the role of biodiesel and biolubricants can be promising, offering multiple advantages but also some challenges like their low oxidation stability. The use of antioxidants can offset this disadvantage, improving the general performance of these products during storage or usage. The aim of this work was to assess the combined and separate use of two different antioxidants (propyl gallate, PG, and tert-butylhydroquinone, TBHQ) on biodiesel and biolubricant based on waste cooking oil (WCO), carrying out a thorough characterization of these products and quantification of antioxidants through voltammetry techniques. Thus, the innovation of this work consists in the use of combined antioxidants and its simultaneous quality assessment and quantification. As a result, the combined use of antioxidants did not offer a synergistic effect, and the use of PG at low concentrations (300 ppm) is recommended in the case of WCO biolubricant. Voltammetry was a suitable and fast method to quantify both PG and TBHQ. [ABSTRACT FROM AUTHOR]

Benezediols are widely used in different areas of industry, thus identification and quantification of benzenediols is of utmost importance due to their toxicity and high environmental abundance. In this work, benzenediol isomers (pyrocatechol, resorcinol, and hydroquinone) were investigated by using the Bray–Liebhafsky (BL) oscillatory reaction. All three isomers exhibit different behavior in the BL reaction, which renders the BL system applicable as a chemosensor. The period between the fifth and sixth oscillation, the amplitude of the sixth oscillation and in the case of hydroquinone, the emergence of a new oscillation in the BL reaction were selected as the parameters used for the identification and quantification of these isomers. Furthermore, electron paramagnetic resonance spectroscopy and DFT calculations were performed in order to provide insights into the mechanism of benzenediols reactions with the BL system. [ABSTRACT FROM AUTHOR]

Effectively detecting catechol (CC) and hydroquinone (HQ) simultaneously is crucial for environmental protection and human health monitoring. In the study presented herein, a novel electrochemical sensor for the sensitive simultaneous detection of CC and HQ was constructed based on an electrochemically reduced graphene oxide (ERGO)-modified multi-walled carbon nanotube paste electrode (MWCNTPE). Scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and electrochemical techniques were utilized to characterize the sensing interface and investigate the sensing mechanism. Under the optimal detection conditions, the oxidation peak currents of CC and HQ show a good linear relationship with their concentrations in the range of 0.4–400 μM with a detection limit of 0.083 μM for CC and 0.028 μM for HQ (S/N = 3). Moreover, the sensor exhibits good performance and can be applied successfully in the simultaneous detection of CC and HQ in tap water samples and urine samples with satisfactory results, indicating its promising application prospects. [ABSTRACT FROM AUTHOR]

Abiotic humification, dominated by catalytic oxidation, is one of the critical mechanisms for organic carbon preservation in nature. However, the effects of biochar catalysis on abiotic humification have not yet been elucidated. This study investigated the catalytic power of biochar from walnut shells at different temperatures (300 °C, 600 °C, and 900 °C) for the abiotic transformation of hydroquinone (HQ) as a representative polyphenol. All the biochar samples catalyzed HQ polymerization, resulting in the formation of humic polymers such as fulvic acids (FAs) and humic acids (HAs). Light and oxygen promoted HA formation. HO• was detected in the BC600–HQ reaction system, and HO• quenching resulted in a 41.22% decrease in HA production, indicating that HO• plays a major role in the oxidative polymerization. In the proposed pathway for the abiotic humification, biochar active sites and generated reactive oxygen species accept an electron from HQ, resulting in oxidation to (semi)quinone radicals, which subsequently undergo cleavage or a coupling reaction to form the oligomerized products. Under BC600 catalysis, the weight-average molecular weight (Mw) of the reaction products of HQ, glucose, and glycine reached 14,449 Da. These findings provide new insights into the application potential of biochar for promoting soil carbon sequestration. [ABSTRACT FROM AUTHOR]

Prolonged exposure to hydroquinone (HQ), a metabolite of benzene, can cause severe haematologic disorders in humans. However, the mechanism is still unclear. In the present study, we investigated whether HQ can induce haematological diseases through ferroptosis, which is another form of cell death apart from apoptosis. The results showed that HQ inhibited the viability of Jurkat cells in a dose-dependent and time-dependent manner. The half inhibitory concentrations (IC50s) of HQ-treated Jurkat cells for 12 h, 24 h and 48 h were 107.16 μmol/L, 33.29 μmol/L, and 14.78 μmol/L. The exposure of Jurkat cells to HQ increased intracellular Fe 2 + , malondialdehyde (MDA) and lipid reactive oxygen species (ROS) levels and down-regulated glutathione (GSH) levels. We used erastin-treated cells as a positive control and cells treated with HQ combined with deferoxamine mesylate (DFO) and ferrostain-1 (Fer-1)-treated cells as the negative controls. DFO and Fer-1 partially restored the degradation of cell viability and GSH content and the accumulation of Fe 2 + , MDA and lipid ROS caused by HQ. In addition, we found that cellular mitochondria in the HQ-treated group showed a decrease in volume, an increase in the density of the bilayer membrane and a decrease or disappearance of mitochondrial cristae. Changes in the erastin-treated group were similar to those in the HQ-treated group. We inferred that HQ induces ferroptosis in Jurkat cells. Subsequently, we found that HQ up-regulated the levels of transferrin receptor 1 (TFRC) mRNA and protein expression and down-regulated FTH1, SLC7A11 and synthetic substrate of antioxidant enzyme 4 (GPX4) mRNA levels and protein expression levels. However, the exposure of Jurkat cells to HQ with DFO and Fer-1 alleviated these changes. Notably, the activation of TFRC and the inhibition of FTH1 and System X c − (cystine–glutamate reverse transporter protein) /GPX4 were associated with HQ-induced ferroptosis. These results provide novel insights into how HQ exacerbates haematopoietic cytotoxicity and provide potential targets for the prevention of HQ-induced diseases. [ABSTRACT FROM AUTHOR]

The microsomal metabolism of phenol (11 °C) over an annual reproductive cycle from June to December was studied using fall spawning adult brook trout (Salvelinus fontinalis). Hepatic microsomes were isolated from three male and three female fish each month. Incubations were optimized for time, cofactor concentration, pH, and microsomal protein concentration. The formation of phase I ring-hydroxylation metabolites, i.e., hydroquinone (HQ) and catechol (CAT), was quantified by HPLC with dual-channel electrochemical detection. Sample preparation and chromatographic conditions were optimized to achieve the separation and sensitivity required for the analysis of these labile products. Biotransformation of phenol over a range of substrate concentrations (1 to 150 mM) was quantified for the calculation of Michaelis–Menten constants (Km and Vmax) for each month. Results indicate a nearly equal production of HQ and CAT among males and females in late June. At the peak of maturity in October, there was an approximate ten-fold greater production of ring-hydroxylation metabolites noted in females in comparison with males on a total liver basis. In vitro phase II biotransformation of phenol glucuronidation was assessed by determining the Michaelis–Menten constants (Km, Vmax) using brook trout hepatic microsomes over a range of substrate concentrations (1 to 60 mM). Initially, there were no significant differences in the glucuronide rate of formation (pmol/min/mg protein) or total capacity (nmol/min/liver) between females and males. At the peak of maturation, the maximum rate of glucuronide formation was 4-fold less in females; however, the total capacity was 2-fold less in females due to the increased liver size in the females. The alterations in biotransformation coincided with increases in the hepatic and gonadal somatic indices and with changes in plasma hormone concentrations. These experiments provide insight into the metabolic deactivation of xenobiotics and to provide data for the prediction of altered hepatic biotransformation rates and pathways during the reproductive cycle. [ABSTRACT FROM AUTHOR]

We describe two operating modes for the same potentiostat, where the redox processes of hydroquinone in a hydrochloric acid medium are contrasted for cyclic voltammetry (CV) as functions of a digital/staircase scan and an analogue/linear scan. Although superficially there is not much to separate the two modes of operation as an end user, differences can be seen in the voltammograms while switching between the digital and analogue modes. The effects of quantization clearly have some impact on the measurements, with the outputs between the two modes being a function of the equivalent-circuit model of the electrochemical system under investigation. Increasing scan rates when using both modes produces higher peak redox currents, with the differences between the analogue and digital modes of operation being consistent as a function of the scan rate. Differences between the CV loops between the analogue and digital modes show key differences at certain points along the scans, which can be attributed to the nature of the electrolyte affecting the charging and discharging processes and consequently changing the peak currents of the redox processes. The faradaic processes were shown to be independent of the scan rates. Simulations of the equivalent-circuit behaviour show differences in the responses to different input signals, i.e., the step and ramp responses of the system. Both the voltage and current steps and ramp responses showed the time-domain behaviour of distinct elements of the equivalent electrochemical circuit model as an approximation of the applied digital and analogue CV input signals. Ultimately, it was concluded that similar parameters between the two modes of operation available with the potentiostat would lead to different output voltammograms and, despite advances in technology, digital systems can never fully emulate a true analogue system for electrochemical applications. These observations showcase the value of having hardware capable of true analogue characteristics over digital systems. [ABSTRACT FROM AUTHOR]

Melasma, also known as chloasma and the "mask of pregnancy", is a common acquired pigmentary disorder characterized by irregular, hyperpigmented brown-to-grey patches primarily situated on the face. It typically affects women of reproductive age, especially those exhibiting Fitzpatrick skin types III to V. The precise etiopathogenesis of melasma is complex and has not been fully elucidated; however, ultraviolet radiation, hormonal factors, and genetic predispositions significantly contribute to the melanin production increase associated with this condition. Due to the multifactorial aetiology, resistance to various therapeutic options, and high recurrence rate, treating melasma is challenging. Hydroquinone has long been considered a gold standard in melasma treatment due to its ability to inhibit tyrosinase; however, it has faced scrutiny after concerns about its adverse effects. Current treatment strategies include various topical and systemic therapies, procedural interventions, as well as combinations of these methods. For optimal results, both photoprotection and a treatment plan that targets different pathogenic mechanisms should be used. Additionally, treatment should be tailored to patient characteristics, such as skin type, the severity of the condition, and compliance. This review summarises current treatment options, focusing on long-term therapy and the latest advancements in managing this challenging condition. [ABSTRACT FROM AUTHOR]

As a critical step in advancing the simulation of photosynthetic complexes, we present the Martini 3 coarse-grained (CG) models of key cofactors associated with light harvesting (LHCII) proteins and the photosystem II (PSII) core complex. Our work focuses on the parametrization of beta-carotene, plastoquinone/quinol, violaxanthin, lutein, neoxanthin, chlorophyll A, chlorophyll B, and heme. We derived the CG parameters to match the all-atom reference simulations, while structural and thermodynamic properties of the cofactors were compared to experimental values when available. To further assess the reliability of the parameterization, we tested the behavior of these cofactors within their physiological environments, specifically in a lipid bilayer and bound to photosynthetic complexes. The results demonstrate that our CG models maintain the essential features required for realistic simulations. This work lays the groundwork for detailed simulations of the PSII-LHCII super-complex, providing a robust parameter set for future studies. [ABSTRACT FROM AUTHOR]

The in vitro biotransformation of phenol at 11 °C was studied using pre-spawn adult rainbow (Oncorhynchus mykiss) (RBT), brook (Salvelinus fontinalis) (BKT), and lake trout (Salvelinus namaycush) (LKT) hepatic microsomal preparations. The incubations were optimized for time, cofactor concentration, pH, and microsomal protein concentration. Formation of Phase I ring-hydroxylation and Phase II glucuronidation metabolites was quantified using HPLC with dual-channel electrochemical and UV detection. The biotransformation of phenol over a range of substrate concentrations (1 to 180 mM) was quantified, and the Michaelis–Menten kinetics constants, Km and Vmax, for the formation of hydroquinone (HQ), catechol (CAT), and phenylglucuronide (PG) were calculated. Species differences were noted in the Km values for Phase I enzyme production of HQ and CAT, with the following rank order of apparent enzyme affinity for substrate: RBT > BKT = LKT. However, no apparent differences in the Km for Phase II metabolism of phenol to PG were detected. Conversely, while there were no apparent differences in Vmax between species for HQ or CAT formation, the apparent maximum capacity for PG formation was significantly less in LKT than that observed for RBT and BKT. These experiments provide a means to quantify metabolic activation and deactivation of xenobiotics in fish, to compare activation and deactivation reactions across species, and to act as a guide for future predictions of new chemical biotransformation pathways and rates in fish. These experiments provided the necessary rate and capacity (Km and Vmax) inputs that are required to parameterize a fish physiologically based toxicokinetic (PB-TK) model for a reactive chemical that is readily biotransformed, such as phenol. In the future, an extensive database of these rate and capacity parameters on important fish species for selected chemical structures will be needed to allow the effective use of predictive models for reactive, biotransformation chemicals in aquatic toxicology and environmental risk assessment. [ABSTRACT FROM AUTHOR]

Catechol (CT) is a phenolic compound widely used in various industrial sectors, but it is toxic; thus, there is a need for methods that aim to identify and quantify the existence of residues of this material in the environment. In this study a disposable printed electrochemical sensor was developed as an effective alternative for determining CT in water samples. The electrode, called SPEC, was manufactured using the screen-printing method using polyethylene terephthalate (PET) as a support, in which a conductive ink based on carbonaceous materials was used to print the working and auxiliary electrodes and a silver/silver chloride of ink on the reference electrode. The optimal ratio for the conductive ink was 6.25% carbon black, 35.42% graphite, and 58.33% nail polish. The ink obtained was characterized by scanning electron microscopy (SEM). The assessment of the effect of pH on the redox process showed Nernstian behavior (0.057 V pH−1), indicating that the process involves the same number of protons and electrons. Under optimized conditions, with 0.2 mol L−1 acetate buffer at pH 5.0, and by square wave voltammetry, the sensor presented sensitivity values of 0.31 μA L μmol−1, a detection limit of 5.96 μmol L−1, and a quantification limit of 19.87 μmol L−1. The sensor was applied to determine CT in tap water samples, and the results showed recoveries between 97.95 and 100.17%. [ABSTRACT FROM AUTHOR]

Glucosamine–chitosan synthesized by the Maillard reaction was combined with montmorillonite to obtain a nanohybrid composite to immobilize horseradish peroxidase. The material combines the advantageous properties of clay with those of the chitosan derivative; has improved water solubility and reduced molecular weight and viscosity; involves an eco-friendly synthesis; and exhibits ion exchange capacity, good adhesiveness, and a large specific surface area for enzyme adsorption. The physicochemical characteristics of the composite were analyzed by infrared spectroscopy and X-ray diffraction to determine clay–polycation interactions. The electrochemical response of the different polyphenols to glassy carbon electrodes modified with the composite was evaluated by cyclic voltammetry. The sensitivity and detection limit values obtained with the biosensor toward hydroquinone, chlorogenic acid, catechol, and resorcinol are (1.6 ± 0.2) × 102 µA mM−1 and (74 ± 8) nM; (1.2 ± 0.1) × 102 µA mM−1 and (26 ± 3) nM; (16 ± 2) µA mM−1 and (0.74 ± 0.09) μM; and (3.7± 0.3) µA mM−1 and (3.3 ± 0.2) μM, respectively. The biosensor was applied to quantify polyphenols in pennyroyal and lemon verbena extracts. [ABSTRACT FROM AUTHOR]

The present work used the Behnajady–Modirshahla–Ghanbary (BMG) kinetic model to determine the initial reaction rates (1/m), which were used to calculate the activation energy (Ea) from the decolorization of synthetic dyes by Fenton processes (Fe2+/H2O2, Fe2+/H2O2/reducer and Fe3+/H2O2/reducer). When increasing the temperature and adding Fe3+-reducing compounds (3-Hydroxyanthranilic Acid, Hydroquinone, Gallic Acid, Cysteine or Ascorbic Acid), increases in the 1/m values were observed. When studying the classical Fenton reaction (Fe2+/H2O2), almost all added reducers had decreased Ea. For example, 3-Hydroxyanthranilic Acid decreased the Ea related to the decolorization of the Phenol Red dye by 39%, while Ascorbic Acid decreased the Ea of Safranin T decolorization by 23%. These results demonstrate that the reducers increased the initial reaction rate and decreased the energy barrier to improve Fenton-based decolorization of dyes. When comparing the reaction systems in presence of reducers (Fen+/H2O2/reducer), the reactions initially containing Fe2+ presented lower Ea than reactions catalyzed by Fe3+. That way, the activation energy obtained through the 1/m values of the BMG model highlighted the pro-oxidant effect of reducers in Fenton processes to degrade dyes. [ABSTRACT FROM AUTHOR]

The reliable detection of environmental contaminants can correctly forecast the degree of environmental pollution that has occurred, which contributes to improving the environmental purification rate and maintaining the ecological balance. Herein, a novel hierarchical biomimetic catalysis MnO2@CuAl-CLDHs was designed and synthesized using a facile method, which exhibited significantly enhanced peroxidase-like activity due to the unique composition and hierarchical mesoporous structure. Under optimized operational conditions, a visible colorimetric array based on the superior nanozyme activity of MnO2@CuAl-CLDHs was developed for the quantitative determination of hydroquinone with a wide linear detection range (1–100 μM) and a low detection limit (0.183 μM). Simultaneously, our presented strategy could analyze hydroquinone in real water samples with high accuracy. Therefore, the bimetallic co-catalyzed nanozymes are expected to be the perfect replacement for natural enzymes to develop convenient and efficient sensors. [ABSTRACT FROM AUTHOR]

We describe the creation of a conductive microcavity based on the assembly of two pieces of carbon nanotube buckypaper for the entrapment of two enzymes, horseradish peroxidase (HRP) and glucose oxidase (GOx), as well as a redox mediator: 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid diammonium salt (ABTS). The hollow electrode, employing GOx, HRP, and the mediator, as an electrochemical enzyme cascade model, is utilized for glucose sensing at a potential of 50 mV vs. Ag/AgCl. This bienzyme electrode demonstrates the ability to oxidize glucose by GOx and subsequently convert H2O2 to water via the electrical wiring of HRP by ABTS. Different redox mediators (ABTS, potassium hexacyanoferrate (III), and hydroquinone) are tested for HRP wiring, with ABTS being the best candidate for the electroenzymatic reduction of H2O2. To demonstrate the possibility to optimize the enzyme cascade configuration, the enzyme ratio is studied with 1 mg HRP combined with variable amounts of GOx (1–4 mg) and 2 mg GOx combined with variable amounts of HRP (0.5–2 mg). The bienzyme electrode shows continuous operational stability for over a week and an excellent storage stability in phosphate buffer, with a decay of catalytic current by only 29% for 1 mM glucose after 100 days. [ABSTRACT FROM AUTHOR]

Despite widespread industrial use, the environmental safety of hydroquinone (HQ), a benzene compound from plants used in processes like cosmetics, remains uncertain. This study evaluated the ecotoxicological impact of HQ on soil and river environments, utilizing non-target indicator organisms from diverse trophic levels: Daphnia magna, Aliivibrio fischeri, Allium cepa, and Eisenia fetida. For a more environmentally realistic assessment, microbial communities from a river and untreated soil underwent 16S rRNA gene sequencing, with growth and changes in community-level physiological profiling assessed using Biolog EcoPlate™ assays. The water indicator D. magna exhibited the highest sensitivity to HQ (EC50 = 0.142 µg/mL), followed by A. fischeri (EC50 = 1.446 µg/mL), and A. cepa (LC50 = 7.631 µg/mL), while E. fetida showed the highest resistance (EC50 = 234 mg/Kg). Remarkably, microbial communities mitigated HQ impact in both aquatic and terrestrial environments. River microorganisms displayed minimal inhibition, except for a significant reduction in polymer metabolism at the highest concentration (100 µg/mL). Soil communities demonstrated resilience up to 100 µg/mL, beyond which there was a significant decrease in population growth and the capacity to metabolize carbohydrates and polymers. Despite microbial mitigation, HQ remains highly toxic to various trophic levels, emphasizing the necessity for environmental regulations. [ABSTRACT FROM AUTHOR]

The terminal oxidases of bacterial aerobic respiratory chains are redox-active electrogenic enzymes that catalyze the four-electron reduction of O2 to 2H2O taking out electrons from quinol or cytochrome c. Living bacteria often deal with carbon monoxide (CO) which can act as both a signaling molecule and a poison. Bacterial terminal oxidases contain hemes; therefore, they are potential targets for CO. However, our knowledge of this issue is limited and contradictory. Here, we investigated the effect of CO on the cell growth and aerobic respiration of three different Escherichia coli mutants, each expressing only one terminal quinol oxidase: cytochrome bd-I, cytochrome bd-II, or cytochrome bo3. We found that following the addition of CO to bd-I-only cells, a minimal effect on growth was observed, whereas the growth of both bd-II-only and bo3-only strains was severely impaired. Consistently, the degree of resistance of aerobic respiration of bd-I-only cells to CO is high, as opposed to high CO sensitivity displayed by bd-II-only and bo3-only cells consuming O2. Such a difference between the oxidases in sensitivity to CO was also observed with isolated membranes of the mutants. Accordingly, O2 consumption of wild-type cells showed relatively low CO sensitivity under conditions favoring the expression of a bd-type oxidase. [ABSTRACT FROM AUTHOR]

In this study, we propose an eco-friendly method for synthesizing cerium tungstate nanoparticles using hydrothermal techniques. We used scanning, transmission electron microscopy, and X-ray diffraction to analyze the morphology of the synthesized nanoparticles. The results showed that the synthesized nanoparticles were uniform and highly crystalline, with a particle size of about 50 nm. The electrocatalytic properties of the nanoparticles were then investigated using cyclic voltammetry and electrochemical impedance spectroscopy. We further used the synthesized nanoparticles to develop an electrochemical sensor based on a carbon paste electrode that can detect hydroquinone. By optimizing the differential pulse voltammetric method, a wide linearity range of 0.4 to 45 µM and a low detection limit of 0.06 µM were obtained. The developed sensor also expressed excellent repeatability (RSD up to 3.8%) and reproducibility (RSD below 5%). Interferences had an insignificant impact on the determination of analytes, making it possible to use this method for monitoring hydroquinone concentrations in tap water. This study introduces a new approach to the chemistry of materials and the environment and demonstrates that a careful selection of components can lead to new horizons in analytical chemistry. [ABSTRACT FROM AUTHOR]

This study was performed to investigate the content of selected phenolic compounds, antioxidant activity and the levels of arbutin and hydroquinone in 25 varieties of highbush blueberry (Vaccinium corymbosum) leaf samples. An analysis of the bioactive components was performed using the HPLC technique and the antioxidant activity was determined via spectrophotometric methods. The content of chlorogenic acid in the analysed leaf extracts ranged from 52.76 mg/g (Spartan variety) to 32.37 mg/g (Nelson variety) and was present in the highest concentration among all the analysed phenolic acids. Particularly large levels of isoquercetin were found in the Aurora, Ivanhoe and Toro varieties (28.40 mg/g, 26.24 mg/g and 21.57 mg/g, respectively). An exceptionally high rutin content (p < 0.05) was found in the Ivanhoe variety (27.19 mg/g) as compared to the other varieties, where it ranged from 2.06 mg/g (Earliblue and Patriot varieties) to 10.55 mg/g (Bluejay variety). The Patriot variety was determined to possess the highest antioxidative activity using the FRAP method (1086.15 μmol Trolox/g d.w.) and based on its DPPH radical scavenging activity (1124.17 μmol Trolox/g d.w.). The total phenolic content (TPC) determined via spectrophotometry ranged from 48.11 mg GAE/g d.w. (Elizabeth variety) to 177.31 GAE/g d.w. (Patriot variety). The arbutin content in the leaves of all tested varieties exceeded 2%, so it can be concluded that they constitute a stable source of arbutin. Three varieties (Bonus, Chanticleer and Herbert) can be considered a potential alternative to bearberry and lingonberry leaves. The hydroquinone content in the analysed extracts was determined to be at a lower level. V. corymbosum leaves can be considered an interesting herbal material for use in traditional herbal medicinal products but not directly for food products and dietary supplements. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the biotransformation capabilities of a hydroquinone-tolerant Digitalis purpurea cell line (DpHQ) for bioconverting hydroquinone (HQ) into arbutin, a compound with significant therapeutic and cosmetic applications. The research evaluated the influence of various HQ concentrations, feeding protocols, and carbon sources on arbutin bioconversion yield. By using HPLC-MS for the quantification of arbutin in biomass and medium, the study revealed that higher precursor (HQ) concentration led to a more pronounced growth inhibition under single dosing than sequential dosing. At lower sugar (3%) and precursor (4 mM HQ) levels, arbutin predominantly remained within the cells, whereas higher sugar (6%) and HQ (5–6 mM) levels promoted its release into the medium. Arbutin production ranged from 591 mg/L under single dosing to 3049 mg/L with sequential dosing, with the highest yield being achieved with 5 mM HQ in divided doses and 6% glucose. This study holds novelty for being the first to demonstrate the DpHQ's tolerance to high concentrations of HQ and its efficient capabilities to bioconvert HQ to arbutin, indicating that D. purpurea is equipped with the enzymes required for this process. These aspects highlight its potential as a biotechnological source for arbutin synthesis. [ABSTRACT FROM AUTHOR]

Mesalamine, also called 5-ASA (5-aminosalicylic acid), is a largely used anti-inflammatory agent and is a main choice to treat Ulcerative Colitis. This report is aimed to investigate enzymatic processes involved in the oxidation of mesalamine to better understand some of its side-effects. Oxidation with oxygen (catalyzed by ceruloplasmin) or with hydrogen peroxide (catalyzed by peroxidase or hemoglobin) showed that these oxidases, despite their different mechanisms of oxidation, could recognize mesalamine as a substrate and trigger its oxidation to a corresponding quinone-imine. These enzymes were chosen because they may recognize hydroquinone (a p-diphenol) as substrate and oxidize it to p-benzoquinone and that mesalamine, as a p-aminophenol, presents some similarities with hydroquinone. The UV-Vis kinetics, FTIR and 1H NMR supported the hypothesis of oxidizing mesalamine. Furthermore, mass spectrometry suggested the quinone–imine as reaction product. Without enzymes, the oxidation process was very slow (days and weeks), but it was markedly accelerated with the oxidases, particularly with peroxidase. Cyclic voltammetry supported the hypothesis of the oxidative process and allowed a ranking of susceptibility to oxidizing mesalamine in comparison with other oxidizable drug molecules with related structures. The susceptibility to oxidation was higher for mesalamine, in comparison with Tylenol (acetaminophen) and with aspirin (salicylic acid). [ABSTRACT FROM AUTHOR]

Abnormal pigmentation or depigmentation of the retinal pigment epithelium (RPE) is a precursor to neovascular age-related macular degeneration (nAMD). In this study, we evaluated the effects of hydroquinone (HQ), the most potent reductant in cigarette smoke, on the melanin production in RPE cells. Induced pluripotent stem cell (iPS)-derived RPE and adult retinal pigment epithelial (ARPE-19) cells were cultured with HQ. Real-time reverse transcription polymerase chain reaction revealed that the expression of melanin-related genes decreased due to the addition of HQ for 1 day. Enzyme-linked immunosorbent immunoassay showed that the concentration of melanin significantly decreased due to the addition of HQ for 24 h. A suspension of RPE cells with HQ for 24 h was prepared, and the absorbance was measured. The absorbance decreased particularly under blue light, suggesting that blue light may reach the choroid and cause choroidal inflammation. Additionally, melanin levels significantly decreased due to the addition of HQ for 1 week. After blue light irradiation on the RPE with HQ for 1 week, the vascular endothelial growth factor in the medium was significantly higher in the HQ group than in the control group. HQ-induced changes in melanin production may be responsible for the uneven pigmentation of the RPE, and these changes may cause nAMD. [ABSTRACT FROM AUTHOR]

The practice of voluntary depigmentation is still prevalent in Africa, with a wide range of lightening cosmetics used. Our objective was to research and quantify three regulated and/or prohibited depigmenting ingredients present in lightening cosmetics sold in Ouagadougou. Twenty-nine lightening cosmetic samples were collected from vendors and HPLC analysis was subsequently conducted to identify and measure the concentrations of hydroquinone, clobetasol propionate, and kojic acid. The presence of hydroquinone was indicated on the label of 13.79% of the products, while 51.72% contained it after analysis. Furthermore, none of the products mentioned a concentration of hydroquinone exceeding 2.00%, even though 27.58% of them contained high concentrations. For clobetasol propionate, its presence was stated on the labels of 13.79% of the products, while 31.03% contained it. One sample had a clobetasol content exceeding 0.05%, although none mentioned a concentration higher than this value. Finally, while 24.13% of the samples claimed to contain kojic acid, only 17.24% did. We also observed that 41.38% of the samples contained combinations of two depigmenting ingredients investigated, with a predominance of the hydroquinone + clobetasol propionate (27.38%). These results demonstrate that manufacturers' declarations regarding the compositions of active ingredients in lightening cosmetics can sometimes be deceptive. [ABSTRACT FROM AUTHOR]

The conversion of metal-organic frameworks (MOFs) into advanced functional materials offers a promising route for producing unique nanomaterials. MOF-derived systems have the potential to overcome the drawbacks of MOFs, such as low electrical conductivity and poor structural stability, which have hindered their real-world applications in certain cases. In this study, laser scribing was used for pyrolysis of a Cu-based MOF ([Cu4{1,4-C6H4(COO)2}3(4,4′-bipy)2]n) to synthesize a Cu-CuO@C composite on the surface of a screen-printed electrode (SPE). Scanning electron microscopy, X-ray diffractometry, and Energy-dispersive X-ray spectroscopy were used for the investigation of the morphology and composition of the fabricated electrodes. The electrochemical properties of Cu-CuO@C/SPE were studied by cyclic voltammetry and differential pulse voltammetry. The proposed flexible electrochemical Cu-CuO@C/SPE sensor for the simultaneous detection of hydroquinone and catechol exhibited good sensitivity, broad linear range (1–500 μM), and low limits of detection (0.39 μM for HQ and 0.056 μM for CT). [ABSTRACT FROM AUTHOR]

The reactions of sterols (androst-5-en-3β-ol-17-one, diosgenin, and cholesterol) and their tosylates with hydroquinone aimed at the synthesis of O,O-1,4-phenylene-linked steroid dimers were studied. The reaction course strongly depended on the conditions used. The study has shown that the major reaction products are the elimination products and unusual steroid dimers resulting from the nucleophilic attack of the hydroquinone C2 carbon atom on the steroid C3 position, followed by an intramolecular addition to the C5–C6 double bond. A different reaction course was observed when montmorillonite K10 was used as a catalyst. The reaction of androst-5-en-3β-ol-17-one under the promotion of this catalyst afforded the O,O-1,4-phenylene-linked steroid dimer in addition to the disteroidal ether. The formation of the latter compound was suppressed by using 3-tosylate as a substrate instead of the free sterol. The reactions of androst-5-en-3β-ol-17-one tosylate and cholesteryl tosylate with hydroquinone catalyzed by montmorillonite K10 carried out under optimized conditions afforded the desired dimers in 31% and 67% yield, respectively. [ABSTRACT FROM AUTHOR]

Inspired by the distinguished regulated photochemical and photophysical properties of 2-(2′-hydroxyphenyl)benzazole derivatives, in this work, the novel bis(2′-benzothiazolyl)hydroquinone (BBTHQ) fluorophore is explored, looking at its photo-induced behaviors associated with different substituted atomic electronegativities, i.e., BBTHQ-SO, BBTHQ-SS and BBTHQ-Se compounds. From the structural changes, infrared (IR) vibrational variations and simulated core-valence bifurcation (CVB) indexes for the dual hydrogen bonds for the three BBTHQ derivatives, we see that low atomic electronegativity could be conducive to enhancing hydrogen bonding effects in the S1 state. Particularly, the O4-H5⋯N6 of BBTHQ-SO and the O1-H2⋯N3 of BBTHQ-SSe could be strengthened to be more intensive in the S1 state, respectively. Looking into the charge recombination induced by photoexcitation, we confirm a favorable ESDPT trend deriving from the charge reorganization of the dual hydrogen bonding regions. By constructing the potential energy surfaces (PESs) along with the ESDPT paths for the BBTHQ-SO, BBTHQ-SS and BBTHQ-Se compounds, we not only unveil stepwise ESDPT behaviors, but also present an atomic electronegativity-regulated ESDPT mechanism. [ABSTRACT FROM AUTHOR]

Herein, a three-dimensional flower-like cobalt-nickel bimetallic metal-organic framework (CoNi-MOF) coupled with two-dimensional graphene oxide (GO) nanocomposites was successfully synthesized for the selective and simultaneous electrochemical determination of catechol (CC) and hydroquinone (HQ). The three-dimensional flower-like structure of the CoNi-MOF/GO nanocomposite has a multilayer structure and a large surface area, which greatly improves its electrocatalytic activity towards CC and HQ. Differential pulse voltammetry (DPV) results showed that the peak-to-peak separation of CC (0.223 V) and HQ (0.120 V) was 103 mV at a CoNi-MOF/GO modified glassy carbon electrode (CoNi-MOF/GO/GCE), suggesting that the proposed modified electrode can selectively and simultaneously determine them. Under optimal conditions, the CoNi-MOF/GO/GCE showed an excellent analytical performance for the simultaneous determination of CC and HQ, including a wide linear range (0.1–100 μM), low detection limit (0.04 μM for HQ and 0.03 μM for CC) and high anti-interference ability. As expected, the developed modified electrode has been used to analyze CC and HQ in river water, with acceptable results. [ABSTRACT FROM AUTHOR]

Hydroquinone poses a major threat to human health and is refractory to degradation, so it is important to establish a convenient detection method. In this paper, we present a novel colorimetric method for the detection of hydroquinone based on a peroxidase-like Pd nanozyme. The vancomycin-stabilized palladium nanoparticles (Van-Pdn NPs, n = 0.5, 1, 2) were prepared using vancomycin as a biological template. The successful synthesis of Van-Pdn NPs (n = 0.5, 1, 2) was demonstrated by UV-vis spectrophotometry, transmission electron microscopy, and X-ray diffraction. The sizes of Pd nanoparticles inside Van-Pd0.5 NPs, Van-Pd1 NPs, and Van-Pd2 NPs were 2.6 ± 0.5 nm, 2.9 ± 0.6 nm, and 4.3 ± 0.5 nm, respectively. Furthermore, Van-Pd2 NPs exhibited excellent biocompatibility based on the MTT assay. More importantly, Van-Pd2 NPs had good peroxidase-like activity. A reliable hydroquinone detection method was established based on the peroxidase-like activity of Van-Pd2 NPs, and the detection limit was as low as 0.323 μM. Therefore, vancomycin improved the peroxidase-like activity and biocompatibility of Van-Pd2 NPs. Van-Pd2 NPs have good application prospects in the colorimetric detection of hydroquinone. [ABSTRACT FROM AUTHOR]

Exogenous ochronosis is a rare dyschromia that primarily impacts those with skin of color. It is characterized by blue–black pigmentation and is associated with the long-term application of skin-lightening creams containing hydroquinone. Commonly confused with other dyschromias, the use of skin lightening topicals can cause paradoxical skin darkening in patients with known exogenous ochronosis. This is highly distressing to patients, often worsening the underlying dyschromia and making treatment more difficult. A 10-year retrospective analysis was conducted that revealed 25 patients with exogenous ochronosis. The average patient used a skin lightening cream for 9.2 years, with exogenous ochronosis most commonly arising on the cheeks (68%), forehead (24%), and temples (20%). Furthermore, this study identified that patients with exogenous ochronosis may respond well to treatment with Q-switched Alexandrite laser and microneedling. The incidence of exogenous ochronosis is likely to increase as demographics shift and access to a wide range of over-the-counter topicals becomes more available, both in the United States and worldwide. Therefore, it is imperative to better characterize exogenous ochronosis to identify best treatment practices for all patients. [ABSTRACT FROM AUTHOR]

In this work, the overall adsorption kinetic process of hydroquinone on Phragmites australis biochar (PAC) was analyzed in depth. A 3D mass transfer model of pore volume and surface diffusion was established, and the diffusion mechanism was analyzed. The characterization results show PAC has a higher porosity value, which is conducive to the adsorption of hydroquinone. The adsorption process modeling results show that the combined effect of pore volume diffusion and surface diffusion promotes the total diffusion process of hydroquinone in the PAC particles, and the two mechanisms of pore volume and surface diffusion exist simultaneously. Under the different operating concentrations, the range of surface diffusion coefficient Ds is 2.5 × 10−10–1.74 × 10−9 cm2/s, and the contribution rate of surface diffusion SDCP% is close to 100%, which is much larger than pore volume diffusion, revealing that regardless of the contact time and position, surface diffusion occupies the main position in intraparticle diffusion. [ABSTRACT FROM AUTHOR]

Artificial nanozymes that are based on ferric oxides have drawn enormous attention due to their high stability, high efficiency, and low cost as compared with natural enzymes. Due to the unique optical plasmonic properties, gold nanoparticles (Au NPs) have been widely utilized in the fields of colorimetric, Raman, and fluorescence sensing. In this work, a photo-responsive Au@Fe3O4 nanozyme is prepared with outstanding peroxidase-like activity. The hot electrons of Au NPs that are excited by a surface plasmon resonance (SPR) effect of NPs improve the catalytic activity of Au@Fe3O4 in oxidizing 3,3′,5,5′-tetramethylbenzidine (TMB) and the detection of hydroquinone (HQ). The magnetic separation and reusability of the nanozyme further lower its costs. The detection linear range of the sensor is 0–30 μM and the lowest detection limit is 0.29 μM. Especially in the detection of real water samples, a good recovery rate is obtained, which provides promising references for the development of the HQ detection technology in seawater. [ABSTRACT FROM AUTHOR]

This study addressed the use of manganese dioxide nanorods/graphene oxide nanocomposite (MnO2 NRs/GO) for modifying a glassy carbon electrode (GCE). The modified electrode (MnO2 NRs/GO/GCE) was used as an electrochemical sensor for the determination of hydroquinone (HQ) in water samples. Differential pulse voltammetry (DPV), cyclic voltammetry (CV), and chronoamperometry were used for more analysis of the HQ electrochemical behavior. Analyses revealed acceptable electrochemical functions with lower transfer resistance of electrons and greater conductivity of the MnO2 NRs/GO/GCE. The small peak-to-peak separation is an indication of a rapid electron transfer reaction. Therefore, this result is probably related to the effect of the MnO2 NRs/GO nanocomposite on the surface of GCE. In the concentration range of 0.5 μM to 300.0 μM with the detection limit as 0.012 μM, there was linear response between concentration of HQ and the current. The selectivity of the modified electrode was determined by detecting 50.0 μM of HQ in the presence of various interferent molecules. At the end, the results implied the acceptable outcome of the prepared electrode for determining HQ in the water samples. [ABSTRACT FROM AUTHOR]

A novel antioxidant containing four hydroxyl groups, namely 2,2′-(2-methylpropane-1,3-diyl)bis(hydroquinone) (MPBHQ), was synthesized using hydroquinone and methylallyl alcohol as the raw materials, phosphoric acid as the catalyst, and toluene as the solvent system. The structure of MPBHQ was characterized by mass spectrometry, nuclear magnetic resonance, ultraviolet spectroscopy, and infrared spectroscopy. The results showed that MPBHQ has a good radical scavenging effect, as measured by the ORAC assay, DPPH radical scavenging assay, ABST radical scavenging assay, and Rancimat test. In fatty acid methyl ester and lard without exogenous antioxidants, MPBHQ showed better antioxidant performance than butylated hydroxytoluene (BHT), hydroquinone (HQ), tert-butyl hydroquinone (TBHQ), and propyl gallate (PG), meeting the need for a new antioxidant with better properties to ensure the oxidative stability of lipids and biodiesel. [ABSTRACT FROM AUTHOR]

In situ NMR spectroelectrochemistry is extremely powerful in studying redox reactions in real time and identifying unstable reaction intermediates. In this paper, in situ polymerization synthesis of ultrathin graphdiyne (GDY) nanosheets was realized on the surface of copper nanoflower/copper foam (nano−Cu/Cuf)-based electrode with hexakisbenzene monomers and pyridine. Palladium (Pd) nanoparticles were further deposited onto the GDY nanosheets by the constant potential method. By using this GDY composite as electrode material, a new NMR-electrochemical cell was designed for in situ NMR spectroelectrochemistry measurement. The three-electrode electrochemical system consists of a Pd/GDY/nano−Cu/Cuf electrode as the working electrode, a platinum wire as the counter electrode, and a silver/silver chloride (Ag/AgCl) wire as a quasi-reference electrode, which can be dipped into a specially constructed sample tube and adapted for convenient operation in any commercial high-field, variable-temperature FT NMR spectrometer. The application of this NMR-electrochemical cell is illustrated by monitoring the progressive oxidation of hydroquinone to benzoquinone by controlled-potential electrolysis in aqueous solution. [ABSTRACT FROM AUTHOR]

In this work, a conductive hydrogel was successfully synthesized, taking advantage of the high number density of active amino and hydroxyl groups in carboxymethyl chitosan and sodium carboxymethyl cellulose. These biopolymers were effectively coupled via hydrogen bonding with the nitrogen atoms of the heterocyclic rings of conductive polypyrrole. The inclusion of another biobased polymer, sodium lignosulfonate (LS), was effective to achieve highly efficient adsorption and in-situ reduction of silver ions, leading to silver nanoparticles that were embedded in the hydrogel network and used to further improve the electro-catalytic efficiency of the system. Doping of the system in the pre-gelled state led to hydrogels that could be easily attached to the electrodes. The as-prepared silver nanoparticle-embedded conductive hydrogel electrode exhibited excellent electro-catalytic activity towards hydroquinone (HQ) present in a buffer solution. At the optimum conditions, the oxidation current density peak of HQ was linear over the 0.1–100 μM concentration range, with a detection limit as low as 0.12 μM (signal-to-noise of 3). The relative standard deviation of the anodic peak current intensity was 1.37% for eight different electrodes. After one week of storage in a 0.1 M Tris-HCl buffer solution at 4 °C, the anodic peak current intensity was 93.4% of the initial current intensity. In addition, this sensor showed no interference activity, while the addition of 30 μM CC, RS, or 1 mM of different inorganic ions does not have a significant impact on the test results, enabling HQ quantification in actual water samples. [ABSTRACT FROM AUTHOR]

Zonarol, which was discovered in the brown algae Dictyopteris undulata, has antibiotic, antioxidative, anti-inflammatory, and neuroprotective hydroquinone properties. Additionally, a daily treatment of zonarol taken orally has been proven to prevent ulcerative colitis and nonalcoholic fatty liver disease in experimentally induced mice models. In this study, to elucidate the physiological behavior of zonarol in vivo, the establishment of quantitative methods for the determination of zonarol in biological samples and basic pharmacokinetics parameters after oral or intravenous administration with purified zonarol to mice were investigated. The zonarol (20–600 ng/mL) in this study was dose-dependently detected using an HPLC-FI system as a single peak on the ODS column with 80% aqueous methanol at 332 nm with an excitation of 293 nm. The pharmacokinetic parameters were derived from a non-compartment analysis of the plasma concentration of zonarol following oral or intravenous treatment in mice. The absolute bioavailability of zonarol was calculated as 25.0%. Interestingly, the maximal distribution of zonarol in the brain (2.525 ± 1.334 µg/g tissue) at 30 min was observed to be higher and slower than that in the liver and kidney at 15 min after bolus intravenous administrations to the mice (10 mg/kg BW). Based on these results, zonarol might be a candidate for a potential drug, an effective tool for drug delivery, or enhancing the treatment of cerebral disease. [ABSTRACT FROM AUTHOR]

35884260 7 Youssef J., Zhu S., Crunteanu A., Orlianges J.-C., Ho H.-P., Bachelot R., Zeng S. Highly Sensitive Plasmonic Biosensors with Precise Phase Singularity Coupling on the Metastructures. Nanomaterials have been widely exploited in the preparation of sensors and biosensors owing to their excellent features, such as high surface area, quantum size effect, and active surface [[3]]. The identification of the target molecule is required for rapid and reliable clinical diagnosis and disease monitoring [[1]]. The findings reported in this Special Issue suggest that nanomaterials possess the potential to be used for the development of various electrochemical sensors and biosensors. [Extracted from the article]

Umbrella Sampling Molecular Dynamics has been used to determine transition energies for different guest molecules through hydroquinone β -clathrate nanochannels, as well as their temperature trend. This clathrate has been shown to successfully enclathrate different types of small gases with remarkable selectivity, and thus it has been proposed as a potential gas separation and storage medium. Most of these potential guest gases can be successfully modeled as single Lennard–Jones spheres. Then, to obtain a general view of diffusion probabilities for different potential guest molecules, a comparative study for different virtual guest molecules described by different Lennard–Jones parameters has been performed. A regular temperature trend has been obtained for the transition energies for the molecular model characteristic parameter range explored. Finally, to locate the transition energy values of real gases within the space of phases explored, calculations have been repeated for molecular models of different noble gases and H 2 . The correlation results presented allow a wide interpolation ability for determining the transition energies of potential guest molecules stored or diffusing through the nanochannels of the studied clathrate structure. [ABSTRACT FROM AUTHOR]

Classical melanoma therapy has several side effects that are responsible for a decrease in the final therapeutic efficacy. It is possible that the drug is degraded before reaching the target site and is metabolized by the body itself, resulting in repeated doses being administered throughout the day and a decrease in patient compliance. Drug delivery systems avoid degradation of the active ingredient, improve release kinetics, prevent the drug from being metabolized before reaching the site of action, and improve the safety and efficacy profiles of adjuvant cancer therapy. The solid lipid nanoparticles (SLNs) based on hydroquinone esterified with stearic acid realized in this work represent a chemotherapeutic drug delivery system that is useful in the treatment of melanoma. The starting materials were characterized by FT-IR and 1H-NMR, while the SLNs were characterized by dynamic light scattering. In efficacy studies, their ability to influence anchorage-dependent cell proliferation was tested on COLO-38 human melanoma cells. Furthermore, the expression levels of proteins belonging to apoptotic mechanisms were determined by analyzing the role of SLNs in modulating the expression of p53 and p21WAF1/Cip1. Safety tests were conducted to determine not only the pro-sensitizing potential but also the cytotoxicity of SLNs, and studies were conducted to assess the antioxidant and anti-inflammatory activity of these drug delivery. [ABSTRACT FROM AUTHOR]

In the current work, globally based on Koopmans' approximation, local electron transport characteristics of dihydroxybenzenes have been examined using the density functional theory for understanding their antioxidant activity. Our experimental and theoretical studies show that hydroquinone has better antioxidant activities when compared to resorcinol and catechol. To identify the antioxidant sites for each dihydroxybenzene molecule, an average analytical Fukui analysis was used. The typical Fukui analytical results demonstrate that dihydroxybenzene oxygen atoms serve as antioxidant sites. The experimental and theoretical results are in good agreement with each other; therefore, our results are reliable. [ABSTRACT FROM AUTHOR]

Ubiquinone redox chemistry is of fundamental importance in biochemistry, notably in bioenergetics. The bi-electronic reduction of ubiquinone to ubiquinol has been widely studied, including by Fourier transform infrared (FTIR) difference spectroscopy, in several systems. In this paper, we have recorded static and time-resolved FTIR difference spectra reflecting light-induced ubiquinone reduction to ubiquinol in bacterial photosynthetic membranes and in detergent-isolated photosynthetic bacterial reaction centers. We found compelling evidence that in both systems under strong light illumination—and also in detergent-isolated reaction centers after two saturating flashes—a ubiquinone–ubiquinol charge-transfer quinhydrone complex, characterized by a characteristic band at ~1565 cm−1, can be formed. Quantum chemistry calculations confirmed that such a band is due to formation of a quinhydrone complex. We propose that the formation of such a complex takes place when Q and QH2 are forced, by spatial constraints, to share a common limited space as, for instance, in detergent micelles, or when an incoming quinone from the pool meets, in the channel for quinone/quinol exchange at the QB site, a quinol coming out. This latter situation can take place both in isolated and membrane bound reaction centers Possible consequences of the formation of this charge-transfer complex under physiological conditions are discussed. [ABSTRACT FROM AUTHOR]

Exposure to environmental pollutants has a proven detrimental impact on different aspects of human health. Increasing evidence has linked pollution to the degeneration of tissues in the joints, although through vastly uncharacterised mechanisms. We have previously shown that exposure to hydroquinone (HQ), a benzene metabolite that can be found in motor fuels and cigarette smoke, exacerbates synovial hypertrophy and oxidative stress in the synovium. To further understand the impact of the pollutant on joint health, here we investigated the effect of HQ on the articular cartilage. HQ exposure aggravated cartilage damage in rats in which inflammatory arthritis was induced by injection of Collagen type II. Cell viability, cell phenotypic changes and oxidative stress were quantified in primary bovine articular chondrocytes exposed to HQ in the presence or absence of IL-1β. HQ stimulation downregulated phenotypic markers genes SOX-9 and Col2a1, whereas it upregulated the expression of the catabolic enzymes MMP-3 and ADAMTS5 at the mRNA level. HQ also reduced proteoglycan content and promoted oxidative stress alone and in synergy with IL-1β. Finally, we showed that HQ-degenerative effects were mediated by the activation of the Aryl Hydrocarbon Receptor. Together, our findings describe the harmful effects of HQ on articular cartilage health, providing novel evidence surrounding the toxic mechanisms of environmental pollutants underlying the onset of articular diseases. [ABSTRACT FROM AUTHOR]

Exposure to hydroquinone (HQ) can cause various health hazards and negative impacts on the environment. Therefore, we developed an efficient electrochemical sensor to detect and quantify HQ based on palladium nanoparticles deposited in a porous silicon-polypyrrole-carbon black nanocomposite (Pd@PSi−PPy−C)-fabricated glassy carbon electrode. The structural and morphological characteristics of the newly fabricated Pd@PSi−PPy−C nanocomposite were investigated utilizing FESEM, TEM, EDS, XPS, XRD, and FTIR spectroscopy. The exceptionally higher sensitivity of 3.0156 μAμM−1 cm−2 and a low limit of detection (LOD) of 0.074 μM were achieved for this innovative electrochemical HQ sensor. Applying this novel modified electrode, we could detect wide-ranging HQ (1–450 μM) in neutral pH media. This newly fabricated HQ sensor showed satisfactory outcomes during the real sample investigations. During the analytical investigation, the Pd@PSi−PPy−C/GCE sensor demonstrated excellent reproducibility, repeatability, and stability. Hence, this work can be an effective method in developing a sensitive electrochemical sensor to detect harmful phenol derivatives for the green environment. [ABSTRACT FROM AUTHOR]

TiO2 is one of the most investigated materials due to its abundance, lack of toxicity, high faradaic capacitance, and high chemical and physical stability; however, its potential use in energy storage devices is constrained by its high internal resistance and weak van der Waals interaction between the particles. Carbon nanotubes are especially well suited for solving these issues due to their strong mechanical strength, superior electrical conductivity, high electron mobilities, excellent chemical and thermal stability, and enormous specific nanoporous surface. The hydrothermal approach was followed by chemical vapor deposition to produce a network composite of titanium dioxide nanoribbons (TNRs) and multi-walled carbon nanotubes (MWCNTs). The nanocomposite was characterized using a variety of methods. One phase of TiO2-B nanoribbons has porous pits on its surface, and MWCNTs are grown in these pits to produce a network-like structure in the nanocomposite. With a two-electrode supercapacitor configuration, the TNR/CNT gave a gravimetric capacitance of 33.33 F g−1, which was enhanced to 68.18 F g−1 in a redox-active electrolyte containing hydroquinone (HQ). Additionally, the areal capacitance per footprint was increased from 80 mF cm−2 in H2SO4 to 163.63 mF cm−2 in H2SO4/HQ. The TNR/CNT supercapacitor has superior cyclic stability than the previously reported TiO2-based electrodes, with 97.5% capacitance retention after 5000 cycles. Based on these results, it looks like the TNR/CNT supercapacitor could provide portable electronic power supplies with new ways to work in the future. [ABSTRACT FROM AUTHOR]

The aim of this work has been to study the possible degradation path of BPA under the Fenton reaction, namely to determine the energetically favorable intermediate products and to compare the cytotoxicity of BPA and its intermediate products of degradation. The DFT calculations of the Gibbs free energy at M06-2X/6-311G(d,p) level of theory showed that the formation of hydroquinone was the most energetically favorable path in a water environment. To explore the cytotoxicity the erythrocytes were incubated with BPA and three intermediate products of its degradation, i.e., phenol, hydroquinone and 4-isopropylphenol, in the concentrations 5–200 μg/mL, for 1, 4 and 24 h. BPA induced the strongest hemolytic changes in erythrocytes, followed by hydroquinone, phenol and 4-isopropylphenol. In the presence of hydroquinone, the highest level of RONS was observed, whereas BPA had the weakest effect on RONS generation. In addition, hydroquinone decreased the level of GSH the most. Generally, our results suggest that a preferable BPA degradation path under a Fenton reaction should be controlled in order to avoid the formation of hydroquinone. This is applicable to the degradation of BPA during waste water treatment and during chemical degradation in sea water. [ABSTRACT FROM AUTHOR]