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A smartphone-integrated colorimetric sensor is introduced for the rapid detection of phenolic compounds, including 8-hydroquinone (HQ), p-nitrophenol (NP), and catechol (CC). This sensor relies on the peroxidase-mimicking activity of aspartate-based metal–organic frameworks (MOFs) such as Cu-Asp, Ce-Asp, and Cu/Ce-Asp. These MOFs facilitate the oxidation of a colorless substrate, 3,3′,5,5′-tetramethylbenzidine (TMB), by reactive oxygen species (ROS) derived from hydrogen peroxide (H2O2), resulting in the formation of blue-colored oxidized TMB (ox-TMB). Among the synthesized MOFs, Cu/Ce-Asp nanorods had the highest activity, probably due to the synergistic effect of aspartate and copper coordination, as well as their large surface area, which allows for improved electron transport. Consequently, Cu/Ce-Asp nanorods were utilized for the detection of phenolic compounds under optimized conditions. In the presence of phenolic compounds, the interaction between TMB and H2O2 is inhibited, resulting in various colorimetric responses. This method accurately determined HQ, NP, and CC in a linear range of up to 5 μM, with detection limits of 0.30 μM, 0.76 μM, and 0.50 μM, respectively. To facilitate real-time and portable analysis, smartphone technology was integrated for color detection, eliminating the need for expensive and bulky laboratory-based optical instruments. In addition, the sensor was effectively employed for real water sample analysis, yielding satisfactory recovery outcomes. The proposed sensor offers a rapid, user-friendly, and portable method for detecting phenolic compounds, even at low concentrations. This study not only advances the application of MOF-based nanozymes in environmental monitoring but also expands their potential use in other fields. [ABSTRACT FROM AUTHOR]

In this study two new zinc(II) complexes involving oxygen and nitrogen donor sequences derived from 1,4-dihydroquinoxaline-2,3-dione (QXD), o-phenylenediamine (OPD) and hydroquinone (HQ) were synthesized through a template procedure. The structural elucidation of these complexes was carried out using measurement of molar conductance in 1x10-3 M solution of DMSO and various spectral techniques; 1H and 13C NMR, FT-IR, UV-VIS and AAS. The results showed that the zinc(II) ion coordinates with the Schiff base ligands in octahedral geometry, leading to the formation of stable macrocyclic and heterocyclic structures. The cyclic ligand (L) was found to coordinate as NNNN donor, through four imine nitrogen atoms which were formed up on condensation of the -NH2 groups on o-phenylenediamine with C=O group on quinoxaline dione in a 2:2 mole ratio, in the presence of one mole equivalent of ZnCl2 in ethanol medium. It also indicates the formation of a new mixed ligand zinc(II) complex with an OO OO O O coordination around zinc(II). The study contributes to the understanding of the coordination chemistry of zinc(II) with Schiff bases and provides insights into the development of novel zinc-based complex compounds. [ABSTRACT FROM AUTHOR]

We present mixed-valence Cu(I)1Cu(II)2(BTC)2 [henceforth Cu(I / II)-HKUST-1], post-synthetically prepared via the hydroquinone (H2Q) treatment of Cu(II)3(BTC)2 (also referred to as HKUST-1) and its subsequent catalytic activity. This Cu(I / II)-HKUST-1 exhibits exceptional structural integrity and superior catalytic performance in the copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction between phenylacetylene and benzyl azide. These findings highlight the potential of mixed-valence Cu-based MOFs as effective and sustainable heterogeneous catalysts for organic transformations, paving the way for future advancements in MOF-based catalysis. [ABSTRACT FROM AUTHOR]

The oxidation of hydroquinone with hydrogen peroxide in the presence of catalytic amounts of FeSO4 results in complex mixtures of oligomers. The average composition of these products is determined by the molar ratio of reagents and varies from (C6H4O4)n at the hydroquinone to hydrogen peroxide ratio 1 : 3 to (C6H4O6)n at the ratio 1 : 5. A characteristic feature of MALDI mass spectra for polymers is the periodicity of signals. However, no such periodicity is observed for the products of hydroquinone oxidation within the m/z range <1000 Da, indicating the absence of fixed sequences of structural fragments. This unique feature arises from the variable ratios and irregular positions of polyhydroxyphenylene and polyhydroxybenzoquinone fragments. Additionally, several factors contribute to the lack of mass-spectral periodicity, namely, the potential formation of peroxides, the presence of stable hydrates, various types of linkages, and possible interactions between hydroxylated phenylene and benzoquinone fragments. In contrast, for m/z values >1000 Da, MALDI mass spectra exhibit periodicity with a mass difference of Δ(m/z) = 74. This value likely corresponds to the fragment C2H2O3, which is neither a hydroquinone nor a benzoquinone structural unit. Taking into account that an equal Δ(m/z) value is observed for fragment ions in the EI mass spectrum of tetrahydroxy-p-benzoquinone, this gives indirect evidence for the presence of polyhydroxybenzoquinone fragments within the oligomers. A key issue regarding the structure of hydroquinone oxidation products is the type of linkages between the polyhydroxyphenylene and/or polyhydroxybenzoquinone units, which could involve C–C or C–O–C bonds (or both). The available spectral data do not resolve this issue conclusively. However, the presence of a sample of the composition (C6H4O6)n, in which each unit contains six oxygen atoms, suggests that at least one oxygen atom forms a bond between the units, indicating a C–O–C connection. Overall, the unique nature of oligomeric products of hydroquinone oxidation explains their high structural variability and redox properties, which likely contribute to their unique pharmacological characteristics. [ABSTRACT FROM AUTHOR]

Herein, a reliable and selective photoelectrochemical (PEC) sensor for hydroquinone quantitative determination is achieved by combining 0D CdS nanoparticle/3D flower-like ZnIn 2 S 4 microsphere nanocomposite with molecular imprint polymer (MIP) technology. [Display omitted] A novel photoelectrochemical (PEC) sensor was developed for the ultra-sensitive and highly selective detection of hydroquinone (HQ), featuring a composite structure that combines 0D CdS nanoparticles with a 3D flower-like ZnIn 2 S 4 microsphere. The sensor, termed rMIP/CdS/ZnIn 2 S 4 , employed molecularly imprinted polymers (MIPs) to achieve specific recognition of HQ. An p-phenylenediamine (pPD) polymer film was electrochemically polymerized onto the surface of the CdS/ZnIn 2 S 4 composite-coated glassy carbon electrode (GCE). Through hydrogen bonding, HQ molecules were imprinted onto the polymer film. Subsequent elution removed these molecules, leaving behind specific recognition sites, enabling selective detection of HQ. The unique spatial structure and heterojunction properties of the 0D CdS nanoparticle/3D flower-like ZnIn 2 S 4 composite, combined with molecular imprinting, significantly enhanced the photocurrent response and increased the selectivity and sensitivity for HQ detection. Under optimal conditions, the rMIP/CdS/ZnIn 2 S 4 sensor demonstrated a low detection limit (0.7 nmol·L−1, S/N=3) over a wide linear range of 1–1200 nmol·L−1. The sensor was successfully applied to detect HQ in real water samples, showing promise for environmental pollution control applications. [ABSTRACT FROM AUTHOR]

Benzene is a crucial industrial hydrocarbon, posing significant health risks due to its toxic metabolites like hydroquinone (HQ). This study investigates the role of clusterin (CLU) in benzene toxicity by analyzing its protein and mRNA levels, as well as the expression of Bcl-2 and Bax, to evaluate the feasibility of CLU as a biomarker for chronic benzene poisoning. HL-60 cells were induced to differentiate into neutrophil-like cells using 1% Dimethyl Sulfoxide (DMSO). Enzyme-linked immunosorbent assay (ELISA) and RT-PCR were used to analyze CLU protein and mRNA levels. ELISA was employed to detect sCLU protein content in cell culture supernatants, and western blot was used to assess Bcl-2 and Bax expression. The optimal time for 1% DMSO to induce HL-60 cells into neutrophil-like cells was 48 h. As HQ concentration increased, HL-60 cell viability decreased, CLU protein and sCLU protein levels in the supernatant decreased, CLU mRNA levels decreased, Bcl-2 protein expression decreased, and Bax expression increased. HQ exposure reduces CLU protein concentration and mRNA levels in neutrophil-like cells induced from HL-60 cells, indicating that CLU could be a potential biomarker for chronic benzene poisoning. [ABSTRACT FROM AUTHOR]

In the present study, new hydroquinone-based 1,2,3-triazole/amide analogues have been prepared and tested for anticancer and antibacterial potential. The structures of final derivatives were established using various analytical techniques. Compound 8, containing para-bromo-1,2,3-triazole nucleus, showed promising cytotoxicity with IC50 of 0.92, 1.72, and 3.56 μM towards MCF-7, HepG2 and SKOV3 cells, respectively, comparable to standard drug doxorubicin. A chloro-bearing hydroquinone derivative (6) exhibited the highest antibacterial potential against S. aureus (MIC 25 μg/mL) and E.coli (MIC 50 μg/mL), which were equipotent to amoxicillin. In terms of in silico ADME properties, all the derivatives followed Lipinski's rule with zero violations, were flexible and lipophilic, exhibited high gastrointestinal absorption, and could not permeate the blood-brain barrier. In conclusion, these compounds possess good anticancer and antibacterial potential. [ABSTRACT FROM AUTHOR]

Background: Melasma, a condition characterised by hyperpigmented patches on the face, is one of the common skin conditions in women seeking treatment from primary care practitioners (PCPs). Several treatment modalities are available for PCPs as well as dermatologists. Each treatment option has its pros and cons, including accessibility and cost. Objective: This article aims to explore and address the treatment options that PCPs can offer for melasma. Discussion: This article outlines how to offer treatment from the PCP's perspective conveniently and cost-effectively. Combined topical treatment seems to be the first-line form that PCPs can offer and manage in the general practice setting. Of the various treatments available, the triple combination of topical hydroquinone with retinoid and corticosteroid is widely described in the literature. [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]

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]

This study developed a novel paper-based sensor for the simultaneous analysis of ascorbic acid (AA) and hydroquinone (HQ). The sensor utilized polyvinyl alcohol (PVA)-stabilized silver nanoparticles (AgNPs-PVA) as the reagent probe and PVA media acted as the filter for separation of the analytes. Polydimethylsiloxane (PDMS) and ethanol serve as the stationary phase and eluent, respectively, exploiting the differences in analyte reactions and solubility to achieve their separation on the filter paper. The circular sensor's central zone was AA's detection area, while HQ was detected in the outer ring region. AA induced an immediate color change in the test kit, whereas HQ required a 20-minute elution with ethanol followed by colorimetric analysis. All analytes exhibited relative standard deviations of repeatability and reproducibility below 2.7% and 9.5%, respectively. Under optimal conditions, the linear detection range for HQ was 0.2-2.0 mg⋅L− 1, while AA was 0.1-2.0 mg⋅L− 1. The detection limit was determined to be 0.05 mg⋅L− 1 for AA and 0.1 mg⋅L− 1 for HQ. The recoveries of AA and HQ in cosmetic cream samples ranged from 80 to 110%. The accuracy of the sensor's measurements was further validated by comparison with the HPLC-DAD method. [ABSTRACT FROM AUTHOR]

In order to study the effects of common ionic components in wastewater on the catalytic performance and salt resistance of the Fe-Bi@γ-Al2O3 catalyst, hydroquinone was selected as the target organic pollutant. Five factors, namely cation species, anion species, total hardness, total alkalinity, and TDS were studied to investigate the effects of different ionic components on the degradation of hydroquinone by the Fe-Bi@γ-Al2O3 catalyst. K+ and Na+ had basically no effect on the COD removal rate, and the COD removal rates were 81.43% and 83.81%, respectively, with no significant change from the COD removal rate from raw water (85.24%), Cu2+ and Al3+ had some inhibitory effect on the COD removal rate, and the COD removal rate was 68.57% and 70.00%, respectively. While, the presence of Fe3+, Cl−, Br− and SiO32− had a significant inhibitory effect on the COD removal rate, and the COD removal rate was 61.90%, 51.90%, 55.71% and 60.48%. The concentration of Ca2+ was 50 mg/L and Mg2+ was 200 mg/L, the COD removal rate was 57.62% and 60.48%, respectively due to water hardness. The alkalinity had an inhibitory effect on the treatment effect of simulated waste water, when the OH concentration was 1500 mg/L, the COD removal rate was 49.05%. The higher the TDS concentration, the more obvious was the inhibitory effect on the COD removal rate, and the COD removal rate was 41.43% when the TDS was 50,000 mg/L. The intermediates and possible degradation mechanisms after catalytic ozone oxidation of hydroquinone-simulated wastewater by Fe-Bi@γ-Al2O3 were investigated by UV spectroscopy scanning, 3D fluorescence spectroscopy scanning, and GC–MS scanning. [ABSTRACT FROM AUTHOR]

Hydroquinone is one of the phenolic compounds which is broadly utilized in industries as a raw material for processing. The presence of HQ in the wastewater can cause harmful effects on humans as well as aquatic life. There are enormous analytical methods that have been developed to detect the presence of hydroquinone even at trace levels, but among them, one of the trending methods is electrochemical, which is not only easy to operate but also gives very sensitive and selective results. In the current study, using a microwave-assisted technique, polypyrrole graphene-based nanocomposites were synthesized and then modified on a glassy carbon electrode to serve as a highly efficient replacement for the highly sensitive and selective hydroquinone (HQ) detection in real water samples. Several characterization methods, including Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, and Raman spectroscopy, were used to examine the produced nanocomposite. These techniques revealed the presence of nanosheet-like morphologies in sensing nanomaterials. Meanwhile, the cyclic voltammetric method was used to investigate the electrochemical behavior of the surface-modified glassy carbon electrode and set a linear concentration from 0.06 to 1.4 mM for sensing HQ under optimized conditions. The modified method showed a limit of detection and limit of quantification of 0.04 and 0.13 mM, respectively. Moreover, the present research has developed a reliable, sensitive, and fast method for the electrochemical detection of HQ in real water samples. [ABSTRACT FROM AUTHOR]

Elaborated conditions for lipase‐catalyzed preferential monoacetylation enabled the large‐scale preparation of hydroquinone monoacetate. This product was then applied to the synthesis of tournefolin B, a highly oxygenated prenylated hydroquinone of plant origin (Tournefortia sarmentosa Lam.). During the course of the synthetic transformations, lipase‐catalyzed deacetylation under mild conditions was demonstrated. [ABSTRACT FROM AUTHOR]

Background: Extrachromosomal circular DNA (eccDNA), a novel class of DNA with a circular topological structure, is present in a variety of cancer cells and tissues and may play broad roles in processes ranging from aging to cancer cell heterogeneity through multiple mechanisms. EccDNA has been characterized by profile, structure and function in several prominent studies but its effect on hydroquinone (HQ)-induced malignantly transformed cells (TK6-HQ) is still elusive. Methods: Circle-seq was applied to determine the eccDNA counts and characteristics of TK6-HQ cells. DNA-fluorescence in situ hybridization was used to measure the abundance of eccDNA_DTX1. Differential gene expression analysis was carried out by RNA-seq. Gene expression was quantified by wertern blot and qPCR. Decircularization of eccDNA_DTX1 was achieved by CRISPR/Cas9. Tumorigenicity was evaluated by xenograft assay in BALB/c nude mice. Results: In this study, we characterized the structure of eccDNAs and the function of DTX1-containing eccDNA (eccDNA_DTX1) in TK6-HQ cells. A total of 669,179 eccDNAs were identified, including 901 eccDNAs with different counts. Most of the eccDNAs were < 1000 bp in length and were enriched in four periodic peaks starting at 186 bp with an interval of ~ 180 bp. The genomic distribution of eccDNAs confirmed that eccDNAs could be observed across all chromosomes and had greater enrichment on chromosomes 17, 19, 20, and 22, with abundant Alu repeat elements, introns and CpG islands. By combining the results of the integrated circle-seq analysis of eccDNAs with those from the RNA-seq analysis (differentially expressed genes, 1064 upregulated and 427 downregulated), the authors showed that the transcription of 20 potential coding genes might be driven by eccDNAs. Finally, the knockdown of eccDNA_DTX1 by CRISPR/Cas9 inhibited the growth of TK6-HQ cells in vitro and in vivo by inhibiting the transcription of DTX1 and promoting ferroptosis, and ferroptosis inhibior, Ferrostatin-1, abrogated the proliferation inhibition of eccDNA_DTX1 knockdown. Conclusions: EccDNA_DTX1 promotes cell growth in hydroquinone-induced malignantly transformed cells by regulating the transcription of DTX1 and ferroptosis. This study profiles eccDNA characteristics and defines the role and mechanism of eccDNA_DTX1 for the first time, shedding new light on the relationship between eccDNAs and carcinogenesis. [ABSTRACT FROM AUTHOR]

Although traditional Fe-based nanozymes have shown great potential, generally only a small proportion of the Fe atoms on the catalyst's surface are used. Herein, we synthesized single-atom Fe on N-doped graphene nanosheets (Fe-CNG) with high atom utilization efficiency and a unique coordination structure. Active oxygen species including superoxide radicals (O2•−) and singlet oxygen (1O2) were efficiently generated from the interaction of the Fe-CNG with dissolved oxygen in acidic conditions. The Fe-CNG nanozymes were found to display enhanced oxidase-like and laccase-like activity, with Vmax of 2.07 × 10−7 M∙S−1 and 4.54 × 10−8 M∙S−1 and Km of 0.324 mM and 0.082 mM, respectively, which is mainly due to Fe active centers coordinating with O and N atoms simultaneously. The oxidase-like performance of the Fe-CNG can be effectively inhibited by ascorbic acid (AA) or hydroquinone (HQ), which can directly obstruct the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB). Therefore, a direct and sensitive colorimetric method for the detection of AA and HQ activity was established, which exhibited good linear detection and limit of detection (LOD) of 0.048 μM and 0.025 μM, respectively. Moreover, a colorimetric method based on the Fe-CNG catalyst was fabricated for detecting the concentration of AA in vitamin C. Therefore, this work offers a new method for preparing a single-atom catalyst (SAC) nanozyme and a promising strategy for detecting AA and HQ. [ABSTRACT FROM AUTHOR]

In photosynthesis, light energy is absorbed and transferred to the reaction center, ultimately leading to the reduction of quinone molecules through the electron transfer chain. The oxidation and reduction of quinones generate an electrochemical potential difference used for adenosine triphosphate synthesis. The trafficking of quinone/quinol molecules between electron transport components has been a long‐standing question. Here, an atomic‐level investigation into the molecular mechanism of quinol dissociation in the photosynthetic reaction center–light‐harvesting complex 1 (RC–LH1) supercomplexes from Rhodopseudomonas palustris, using classical molecular dynamics (MD) simulations combined with self‐random acceleration MD‐MD simulations and umbrella sampling methods, is conducted. Results reveal a significant increase in the mobility of quinone molecules upon reduction within RC–LH1, which is accompanied by conformational modifications in the local protein environment. Quinol molecules have a tendency to escape from RC–LH1 in a tail‐first mode, exhibiting channel selectivity, with distinct preferred dissociation pathways in the closed and open LH1 rings. Furthermore, comparative analysis of free energy profiles indicates that alternations in the protein environment accelerate the dissociation of quinol molecules through the open LH1 ring. In particular, aromatic amino acids form π‐stacking interactions with the quinol headgroup, resembling the key components in a conveyor belt system. This study provides insights into the molecular mechanisms that govern quinone/quinol exchange in bacterial photosynthesis and lays the framework for tuning electron flow and energy conversion to improve metabolic performance. [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]

Mayla Barbosa,1 Rebecca Perez de Amorim,1 Daniel Cassiano,2 Marina Dias,1 Ana Flávia de Abreu,1 Edileia Bagatin,2 Hélio Amante Miot,1 Ana Cláudia Cavalcante Espósito1 1Department of Dermatology, Faculdade de Medicina de Botucatu (UNESP), Botucatu, SP, Brazil; 2Department of Dermatology, Universidade Federal de São Paulo (UNIFESP), São Paulo, SP, BrazilCorrespondence: Ana Cláudia Cavalcante Espósito, Department of Dermatology, Faculdade de Medicina de Botucatu, UNESP Medical School, Botucatu, SP, Brazil, Email anaclaudiaesposito@gmail.comBackground: Nicotinamide has demonstrated efficacy in the treatment of melasma. Topical antioxidants and humectants may enhance its performance. Currently, there is no controlled trial on the combination of 10% nicotinamide, 5% magnesium ascorbyl phosphate, and 5% hyaluronic acid, a dermo-cosmetic compound, in comparison to 4% hydroquinone for the treatment of melasma. This study aimed to explore the tolerability and efficacy of the association of the combined product versus hydroquinone.Methods: A randomized, double-blind trial involving women with facial melasma was conducted. Participants were instructed to apply the combined product (NIC group) twice daily or 4% hydroquinone for 60 days (HQ group) at night and placebo in the morning. Evaluations were performed at inclusion, after 14 and 60 days of treatment, measuring the modified Melasma Area and Severity Index (mMASI), Melasma Quality of Life Scale (MELASQoL), and colorimetric luminosity. The Global Aesthetic Improvement Scale (GAIS) was assessed by a blinded evaluator.Results: Both interventions led to a progressive improvement in mMASI, MELASQoL, and GAIS, without a difference between them on D14 and D60 (p> 0.2). For NIC, the mean reduction (95% CI) in mMASI was 16% (8– 24%) on D14 and 32% (23– 41%) on D60, while for HQ, it was 10% (7– 24%) on D14 and 43% (34– 52%) on D60. Reduction in colorimetric luminosity was greater in the HQ group at D60 (p=0.01). No serious side effects were identified. Of the initially included 50 patients, one was lost to follow-up in the HQ group on D60, and one withdrew consent from the NIC group, both unrelated to treatment.Conclusion: The association of 10% nicotinamide, 5% magnesium ascorbyl phosphate, and 5% hyaluronic acid was safe and well-tolerated, although its overall clinical efficacy was numerically inferior to 4% hydroquinone. This regimen can be considered for patients with poor tolerability to hydroquinone.Clinical Trial Registration: &num;RBR-4mkfmr8.Keywords: melasma, hyperpigmentation, nicotinamide, hydroquinone, antioxidants

Background: The mainstay of treatment for melasma is topical hydroquinone or preparations containing hydroquinone. In recent years, cysteamine cream has gained popularity in the treatment of hyperpigmentation disorders. Objectives: This study aimed to compare the efficacy of combined hydroquinone/betamethasone to cysteamine in the treatment of melasma. Methods: Eighteen patients had completed this open-label controlled trial. Subjects received either 5% cysteamine cream or a combination of 4% hydroquinone cream and 0.06% betamethasone valerate for 12 weeks according to standardized protocols. Patients were assessed at recruitment, 4 weeks, and 12 weeks after treatment for Melasma Area and Severity Index (MASI) scores. Other parameters relating to skin complexions and patient satisfaction were also assessed. Results: Patients treated with hydroquinone (n = 7) and cysteamine (n = 11) both showed significant decreases in MASI score at week 12: 33.1% (P = 0.009) and 37.9% (P = 0.009), respectively. There was no statistically significant difference between the two treatment groups (P = 0.236). Melanin content at week 12 decreased by 8.8% (P = 0.016) in the hydroquinone group and 11.5% (P = 0.046) in the cysteamine group, with no significant difference between the groups (P = 0.253). No significant differences were observed between the groups for other parameters or patient satisfaction. Conclusion: Cysteamine cream may provide an alternative treatment option for individuals with melasma, offering fewer side effects while delivering comparable results.

This work demonstrates facile synthesis of Tb-doped ZnO nanoparticles and investigates their structural, optical, electrochemical, photocatalytic, and antibacterial performance. XRD patterns of undoped and doped ZnO nanoparticles confirm a hexagonal wurtzite structure. TEM and SAED reveals that the particle size is 14–38 nm. SEM images show that ZnO and Tb-doped ZnO nanoparticles have smooth surfaces, and elemental composition was confirmed by EDX analysis. UV–Visible spectrophotometry studies, reveals that the band gap narrows with increasing Tb concentration. Photoluminescence spectra at room temperature showed a band at 538 nm, indicating zinc vacancies and green emission. Tb-doped ZnO with x = 0.075 exhibited the highest photocatalytic activity for degrading Rose Bengal dye compared to other photocatalysts. The electrochemical behaviour of Catechol (CC), Hydroquinone (HQ), and Bisphenol-A (BPA) at Tb–ZnO/MCPE was studied. The modified electrode process for CC and BPA was adsorption-controlled, and simultaneous recognition of CC, HQ, and BPA was achieved, showing an increase in current. Electro polymerization of poly (Congo red) on Tb–ZnO/MCPE confirmed clean deposition on the surface, enhancing electrocatalytic activity. The antibacterial efficacy was tested using the traditional disc diffusion method, showing effective inactivation of bacterial strains, including pathogens such as S. aureus (G+) and E. coli (G-). [Display omitted] • This work demonstrates the facile synthesis of ZnO and Tb doped nanoparticles via chemical co-precipitation process. • The XRD pattern appearance hexagonal wurtzite structure. TEM and SAED reveal particle sizes of 14–38 nm. SEM and EDX confirm morphology and elemental composition. • Higher Tb doping exhibit the highest photocatalytic activity in degrading Rose Bengal dye. And the antibacterial activity, tested via disc diffusion, effectively inactivates S. aureus (G+) and E. coli (G−) bacterium. • The sweep rate confirms that the modified electrode process of CC and BPA at the PCRTZO/MCPE was adsorption controlled. Tb–ZnO/MCPE electrode simultaneously detects CC, HQ and BPA with distinct current increases. • Electro polymerization of poly (Congo red) on Tb–ZnO/MCPE confirms Congo red deposition on the electrode surface. [ABSTRACT FROM AUTHOR]

The reaction center-light-harvesting complex 1 (RC-LH1) plays an essential role in the primary reactions of bacterial photosynthesis. Here, we present high-resolution structures of native monomeric and dimeric RC-LH1 supercomplexes from Rhodobacter (Rba.) blasticus using cryo-electron microscopy. The RC-LH1 monomer is composed of an RC encircled by an open LH1 ring comprising 15 aß heterodimers and a PufX transmembrane polypeptide. In the RC-LH1 dimer, two crossing PufX polypeptides mediate dimerization. Unlike Rhodabacter sphaeroides counterpart, Rba. blasticus RC-LH1 dimer has a less bent conformation, lacks the PufY subunit near the LH1 opening, and includes two extra LH1 aß subunits, forming a more enclosed S-shaped LH1 ring. Spectroscopic assays reveal that these unique structural features are accompanied by changes in the kinetics of quinone/quinol trafficking between RC-LH1 and cytochrome bc1. Our findings reveal the assembly principles and structural variability of photosynthetic RC-LH1 supercomplexes, highlighting diverse strategies used by phototrophic bacteria to optimize light-harvesting and electron transfer in competitive environments. [ABSTRACT FROM AUTHOR]

Objective(s): Electrochemical estimation of dopamine by synthesized Pd@Au-PANI nanocomposite. Materials and Methods: Au-doped and Au-Pd incorporated PANI nanocomposites were prepared via oxidative polymerization and hydrothermal methods with ammonium persulphate. Results: As-suggested biosensor was improved for the simultaneous disclosure of dopamine and hydroquinone, displayed low detection limits of 0.46 µM for dopamine and 0.23 mM for hydroquinone. Conclusion: The fabricated biosensor showed broad linear ranges for dopamine (5-25 µM), and hydroquinone (0.5-2.5 mM). Along with these good results, the Au-Pd@PANI nanotube also implemented good stability and reproducibility. [ABSTRACT FROM AUTHOR]

Here we illustrate the use of dimethylglyoximate (DMG) as shape directing agent for the synthesis of nickel oxide nanowires (NiONWs) via hydrothermal process followed by calcination at elevated temperature. As-prepared NiONWs were characterized through scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) techniques and Fourier Transform Infra-red (FTIR) spectroscopy. The surface area of 27 m2 g–1 and pore diameter of 22 nm was true for the product. The prepared NiONWs were drop casted over the active surface of glassy carbon electrode (GCE) to apply it for the electrochemical sensing of hydroquinone based on cyclic voltammetry (CV) and amperometry techniques. The phosphate buffer solution (PBS) of pH 5.8 was used for the measurement of hydroquinone during electrochemical investigation. The developed sensor displayed a wide linear range of 0.5 to 11 µM for hydroquinone detection with sensitivity of 200 µA mM–1 cm–2 and limit of detection (LOD) equal to 0.01 µM. The sensor was further examined and found to be highly stable and extremely selective for the oxidation of hydroquinone. The sensor was successfully applied for amperometric detection of hydroquinone from water samples. [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]

The consumption of styrene epoxide (SE) and hydroquinone (HQ) in a ternary system (TrS) (SE–HQ–Cu(II)) in an oxygen atmosphere in a methanol solution is studied. The oxygen uptake by the SE–HQ–CuCl2 Trs is studied manometrically. The expression of velocity in terms of the reagent concentrations V = k[Cu(II)]1[HQ]0[SE]0 and the effective oxidation rate constant k = 1.82 × 105exp(–40 kJ mol–1/RT) s–1 is obtained in the temperature range 308–323 K. The oxidation mechanism of the TrS is discussed. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of dioxygen (O2) in the presence of benzene‐1,4‐diol (hydroquinone) in N,N‐dimethylformamide (DMF) was examined using cyclic voltammetry and digital simulation techniques. The presence of hydroquinone modified the quasi‐reversible cyclic voltammograms (CV) of O2, resulting in formation of a superoxide radical anion (O2•−), which was scavenged by hydroquinone to form quinone radical anion and hydroperoxide. This reaction proceeded via a two‐proton‐coupled electron transfer (2PCET) mechanism with superior reaction kinetics. Digital simulations of the CVs elucidated the details of the 2PCET process, which involved heterogeneous electrochemical reactions and homogeneous solution reactions between the electrogenerated O2•− and hydroquinone. The thermodynamic and kinetic parameters of 2PCET were obtained from simulation analyses, which included three elementary steps: (i) formation of the prereactive complex from the free reactants, (ii) intracomplex 2PCET forming the product complex via a transition state, and (iii) dissociation of the product complex yielding free products. These parameters provide essential information for the development of artificial electron‐transfer catalysts and electron transfer carriers using hydroquinone derivatives. [ABSTRACT FROM AUTHOR]