Search Results (428)

The interest in the use of phytochemicals and herbal medicines for the treatment of acne vulgaris has grown steadily over recent decades. The research on the secondary metabolites and biological properties of bearberry (Arctostaphylos uva-ursi (L.) Spreng.) has been intensified in recent years, but the range of bacterial strains tested, many of which are highly relevant to human health, remains very limited. Therefore, the aim of this study was to evaluate the chemical composition and the antioxidant, antimicrobial, and cytotoxic activities of water and ethanolic bearberry leaf extracts. Compared with the ethanolic extract, the water extract was characterized by higher concentrations of arbutin, hydroquinone, corilagin, and hyperoside and the absence of ursolic acid and oleanolic acid. However, it exhibited lower total phenolic content and reduced levels of penta-O-galloyl-β-d-glucose (PGG). The ethanolic extract of bearberry leaves showed higher antioxidant activity and the most favorable overall biological properties. The therapeutic index (TI) values for the water and ethanolic extracts, respectively, were as follows: Cutibacterium acnes ATCC 11827 (10.70; 21.57), Propionibacterium acnes PCM 2334 (10.70; 43.13), P. acnes PCM (5.33; 21.57), Staphylococcus aureus ATCC 25923 (10.70; 21.57), and S. epidermidis ATCC 12228 (5.33; 10.78). The present findings further support the medicinal and cosmetic use of A. uva-ursi and highlight its potential as a source of natural antibacterial agents for acne treatment. Full article

Background: Enterococcus faecalis is a major cause of complicated urinary tract infections (UTIs), characterized by intrinsic resistance and pronounced biofilm formation. Nitroxoline (NTX), a metal-chelating uroantiseptic, accumulates in urine and exhibits antibiofilm activity. Hydroquinone (HQ), the active urinary metabolite of arbutin-containing herbal preparations, is also excreted into urine and may contribute to antimicrobial activity in situ. This study investigated the antimicrobial and antibiofilm effects of NTX and HQ, individually and in combination, against uropathogenic E. faecalis isolates. Methods: Minimum inhibitory (MIC), bactericidal (MBC), and anti-adhesion (MAC) concentrations were determined using broth microdilution. Interaction was assessed by the checkerboard method and expressed as the fractional inhibitory concentration index (FICI). Biofilm inhibition was quantified by colony-forming unit (CFU) enumeration following exposure to subinhibitory concentrations. Ultrastructural alterations of E. faecalis following exposure to NTX and HQ were examined by transmission electron microscopy (TEM). Results: NTX demonstrated MIC values ranging from 0.002–0.016 mg/mL (MIC50/MIC90: 0.004/0.008 mg/mL), while HQ exhibited MIC values of 0.78–1.56 mg/mL (MIC50/MIC90: 0.78/1.56 mg/mL). Synergistic interactions (FICI ≤ 0.5) were observed in selected isolates, with up to eightfold and sixteenfold reductions in NTX and HQ concentrations, respectively. Additive effects predominated in the remaining isolates without antagonism. The combination achieved 3–5 log₁₀ reductions in adherent bacterial counts compared to untreated controls and up to 4 log₁₀ reductions compared to single-agent exposure. In several strains, complete inhibition of adhesion was observed. TEM analysis revealed marked envelope disruption, cytoplasmic condensation, and structural collapse following combined treatment. Conclusions: Given that both NTX and HQ are active within the urinary environment, their combination may represent a pharmacologically relevant strategy targeting both bacterial growth and early biofilm establishment in enterococcal UTIs. These findings support further in vivo and pharmacokinetic investigations to evaluate the clinical applicability of this combination. Full article

Three cerium-based metal–organic frameworks (MOFs), Ce-BDC, Ce-BDC-NH₂, and Ce-BTC, were used as catalysts for the hydroxylation of several organic compounds, including those not relevant to environmental or biological systems. Structural characteristics were validated by FT-IR spectroscopy, while SEM imaging demonstrated rod-like morphologies of 100–200 nm in width for Ce-BDC-NH₂ and 50–100 nm for Ce-BTC. The optical properties, ascertained using diffuse reflectance spectra and Tauc analysis, revealed bandgaps of 3.0 eV, 2.9 eV, and 3.6 eV for Ce-BDC, Ce-BDC-NH₂, and Ce-BTC, respectively. Catalytic investigations revealed that Ce-MOFs effectively convert phenol into 1,4-dihydroxybenzene with an efficiency of 86–99%, as confirmed by UV–Vis spectroscopy and HPLC analysis using an authentic hydroquinone (1,4-dihydroxybenzene) standard. The Ce-MOFs efficiently oxidize the dyes methylene blue (MB) and Congo red (CR) and also promote the hydroxylation of L-tyrosine, indicating their relevance to biologically significant substrates. The high catalytic performance of Ce-MOF highlights the potential of Ce-based materials for environmental remediation, chemical transformation, and sustainable wastewater treatment. Full article

Skin-whitening products (SWPs) are widely used, yet many contain prohibited or misdeclared depigmenting agents posing safety concerns. This study developed and validated a sensitive and reliable HPLC-DAD method for the simultaneous determination of hydroquinone (HQ), salicylic acid (SAL), and niacinamide (NIC) in commercial and homemade SWPs. Validation followed ICH Q2(R1), demonstrating good specificity, linearity (R² > 0.9999), method precision (%RSD < 2%), and LOD/LOQ values of 0.2 and 0.7 µg/mL for all analytes. Recoveries of 97.48–99.83% for HQ, 99.37–101.26% for NIC, and 83.04–95.38% for SAL were also obtained. Analysis of 51 products revealed major discrepancies between declared and measured contents. HQ was detected in 18.60% of commercial samples despite its prohibition in OTC cosmetic formulations; none of the SAL-containing products matched their labels, and NIC appeared in 25.58% of samples, with only one sample compliant with its declared content. Homemade products showed undeclared HQ in 62.50% of samples, 25% of samples exceeded the 2% permitted SAL limit, and unregulated multi-ingredient combinations. Risk assessment showed all HQ-containing commercial products and several homemade formulations posed unacceptable systemic exposure risks (MoS < 100). Overall, the proposed method provides a practical and accessible approach for routine quality control and market surveillance of cosmetic products. Full article

The electro-oxidation of eugenol (EUG) natural antioxidant was studied by cyclic voltammetry in phosphate buffer solutions (PBS) of different pH at electrochemically partially reduced graphene oxide (GCE/ePRGO). The voltammetric responses were mainly controlled by adsorption at this modified electrode. Current values were higher at pH 2.0 PBS, therefore, this pH was chosen to perform all experiments. DFT calculations of pKa’s and standard potentials defined the possible pathways of eugenol and its oxidation products. These pathways were evaluated through the comparison of voltammetric simulations of adsorbed species with experiments at pH 2.0, which also allowed for the estimation of the values of the kinetic parameters involved in electrochemistry. Our findings suggest a multi-step redox process in which Eugenol is first oxidized to the radical species and then to a cationic product. At this stage, the pathways branch into to methylenquinone and a 4-allyl-1,2-diquinone molecules. 4-allyl-1,2-diquinone is finally reduced in single or double reversible electrochemical step to the hydroquinone species. The present physicochemical work allows for a deeper understanding of the eugenol oxidation mechanism, which was only partially proposed in previous studies. Full article

This study presents a straightforward process for producing a hybrid ternary composite of silver nanoparticles (Ag NPs), small graphene oxide (s-GO), and zirconia (ZrO₂) and its use as an electrode material for electrochemical sensing. The physico-chemical properties of the ternary composite were analyzed by means of field emission scanning electron microscopy (FE-SEM), ultraviolet-visible (UV-vis) and FTIR spectroscopy, X-ray Photoelectron Spectrometry (XPS) and contact angle (CA) measurements. The synthesized hybrid nanomaterial was employed as an electrode modifier in the fabrication of a modified screen-printed carbon electrode (SPCE) and used for the simultaneous electrochemical sensing of key environmental pollutants such as hydroquinone (HQ) and catechol (CAT). The developed sensor exhibited linearity in the range of 0–100 µM for both HQ and CAT, with sensitivity values of 2640 µA·mM⁻¹·cm⁻² for HQ and 5120 µA·mM⁻¹·cm⁻² for CAT. The limits of detection (LOD) were 1.5 µM for HQ and 0.72 µM for CAT, respectively. The synergistic enhancement of electron transfer kinetics, the increased electroactive surface area, the strong anti-interference capability, and excellent reproducibility and stability establish these modified electrodes as promising candidates for environmental monitoring and real sample analysis. Full article

Polymer gels are widely used for profile control and water shutoff in mature reservoirs, while conventional gels are limited under high temperature due to poor thermal stability. This study develops a high-temperature-resistant gel based on acrylamide/vinylpyrrolidone copolymer (P(AM/NVP)), crosslinked with hydroquinone-hexamethylenetetramine (HQ-HMTA). At 150 °C, the gel achieves a Sydansk strength code of H with a gelation time of 9.5 h, and shows excellent thermal stability, maintaining over 90% weight after 180 days. Rheological and microscopic analyses confirm a dense, stable network with high storage modulus (G′). Core flooding tests demonstrate good injectivity with resistance factors of 3.99~129.93, while the plugging rate exceeds 98%. All the experimental results indicate that the P(AM/NVP)-based gel has great potential for water plugging in high temperature oil reservoirs. Full article

Skin pigmentation results from the melanin production by melanocytes, an essential process for protection against ultraviolet radiation and for maintaining cutaneous homeostasis. Disruptions in this balance lead to pigmentary disorders, such as hyperpigmentation, which is characterized by localized or diffuse darkening of the skin. Its most prevalent forms include melasma, post-inflammatory hyperpigmentation, and solar lentigines, often driven by hormonal, inflammatory, and environmental factors, particularly sun exposure. Despite being clinically benign, these conditions have a significant impact on self-esteem and quality of life. Conventional treatments rely on depigmenting agents such as hydroquinone, retinoids, and corticosteroids, as well as chemical peels, and laser or light-based therapies, frequently used in combination. However, limited efficacy, prolonged treatment durations, and potential adverse effects underscore the need for safer and more effective alternatives. In recent years, research has focused on developing novel approaches, with nanotechnology-based delivery systems and minimally invasive techniques, such as microneedling, standing out as particularly promising fields. In parallel, the growing number of interventional clinical trials reflects an increasing interest in optimizing topical depigmenting strategies. This review summarizes the main types of hyperpigmentation, the depigmenting substances currently used, and emerging therapeutic approaches with potential clinical impact. Full article

Background/Objectives: Manual preparation of semisolid formulations (creams, ointments, gels) is prone to variability in mixing energy and time, which may compromise uniform API distribution. This study aimed to evaluate an Electronic Mortar and Pestle (EMP; Unguator™) as a standardized compounding tool, with objectives to: (i) validate stability-indicating UHPLC methods; (ii) assess content uniformity across jar strata; (iii) quantify the impact of mixing time and rotation speed via design of experiments (DOE); and (iv) verify cleaning effectiveness and cross-contamination risk. Methods: Five representative formulations were compounded: urea 40%, clobetasol 0.05%, diclofenac 2.5% in hyaluronic acid 3% gel, urea 10% + salicylic acid 1%, and hydroquinone 5%. UHPLC methods were validated per ICH Q2(R2) and stress-tested under acid, base, oxidative, thermal, and UV conditions. Homogeneity was assessed by stratified sampling (top/middle/bottom). A 3² factorial DOE (time: 2/6/10 min; speed: 600/1500/2400 rpm) modeled effects on % label claim and RSD. Cleaning validation employed hydroquinone as a tracer, with swab sampling pre-/post-use and post-sanitization analyzed by HPLC. Results: All UHPLC methods met specificity, linearity, precision, accuracy, and sensitivity criteria and were stability-indicating (Rs ≥ 1.5). Formulations achieved 90–110% label claim with strata CV ≤ 5%. DOE revealed speed as the dominant factor for clobetasol, urea, and diclofenac, while time was more influential for salicylic acid; gels exhibited curvature, indicating diminishing returns at high rpm. Model-predicted optima were implementable on the Unguator™ with minor rounding of rpm/time. Cleaning validation confirmed post-sanitization residues below LOQ and <10 ppm acceptance. Conclusions: The Unguator™ provides a practical, parameter-controlled route for compounding pharmacies to standardize semisolid preparations, achieving reproducible layer-to-layer content uniformity within predefined criteria under the evaluated conditions through programmable set-points and validated cycles. DOE-derived rpm–time relationships define an operational design space within the studied ranges and support selection of implementable device settings and set-points. Importantly, the DOE-derived “optima” in this study are optimized for assay-based content uniformity (mean % label claim and strata variability). Cleaning validation supports a closed, low-cross-contamination workflow, facilitating consistent routines for both routine and complex formulations. Overall, the work implements selected QbD elements (QTPP—Quality Target Product Profile; CQA—Critical Quality Attribute definition; CPP—Critical Process Parameter identification; operational design space; and a proposed control strategy) and should be viewed as a step toward broader lifecycle QbD implementation in compounding. Full article

Tyrosinase (EC 1.14.18.1) is a binuclear copper enzyme responsible for the rate-limiting steps of melanogenesis, catalyzing the hydroxylation of L-tyrosine and oxidation of L-DOPA into o-quinones that polymerize melanin. Beyond its physiological role in pigmentation, tyrosinase is also implicated in food browning and oxidative stress–related disorders, making it a key target in cosmetic, food, and biomedical industries. This systematic review, conducted following PRISMA guidelines, aimed to identify and analyze microbial metabolites with tyrosinase inhibitory potential as sustainable alternatives to conventional inhibitors such as hydroquinone and kojic acid. Literature searches in Scopus and Web of Science (March 2025) yielded 156 records; after screening and applying inclusion criteria, 11 studies were retained for analysis. The inhibitors identified include indole derivatives, phenolic acids, peptides, and triterpenoids, mainly produced by fungi (e.g., Ganoderma lucidum, Trichoderma sp.), actinobacteria (Streptomyces, Massilia), and microalgae (Spirulina, Synechococcus). Reported IC₅₀ values ranged from micromolar to milli-molar levels, with methyl lucidenate F (32.23 µM) and p-coumaric acid (52.71 mM). Mechanisms involved competitive and non-competitive inhibition, as well as gene-level regulation. However, methodological heterogeneity, the predominance of mushroom tyrosinase assays, and limited human enzyme validation constrain translational relevance. Computational modeling, site-directed mutagenesis, and molecular dynamics are proposed to overcome these limitations. Overall, microbial metabolites exhibit promising efficacy, stability, and biocompatibility, positioning them as emerging preclinical candidates for the development of safer and more sustainable tyrosinase inhibitors. Full article

Siraitia grosvenorii (Swingle) C. Jeffrey is widely recognized for its anti-inflammatory properties, as well as its roles in lung purification, phlegm elimination, intestinal function regulation, and anti-tumor activity. Its pharmacological activity is attributed to a diversity of functional components. However, due to the extensive application of sweet glycosides in food additives, there have been few studies on non-sweet glycosides, particularly those with high polarity. This paper investigates the chemical constituents in the non-sweet glycosides fraction of S. grosvenorii juice. First, an MCI GEL CHP20P chromatographic column was utilized to enrich the non-sweet glycosides fraction. Furthermore, two-step medium-pressure liquid chromatography (MPLC) was performed for the efficient preparative separation of high-polarity non-sweet glycosides with similar structures, using C18 and silica gel as stationary phases, respectively. Seven non-sweet glycoside compounds were identified through NMR and mass spectrometry analyses, including three new compounds (4-hydroxyphenylethanol 4-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside, 4-hydroxyphenylethanol 4-O-β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside and n-butanol 1-O-β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside), as well as four known ones (α-D-glucopyranosyl-(1→4)-D-glucose, α-D-glucopyranosyl-(1→2)-β-D-fructofuranoside, methoxy hydroquinone diglucoside, and β-D-glucopyranoside). The results demonstrate that mixed-mode MPLC using different stationary phases is an efficient approach for separating non-sweet glycosides from S. grosvenorii. Full article

Additive manufacturing, particularly fused deposition modeling (FDM), has emerged as a promising approach for producing electrochemical sensors based on conductive thermoplastic composites. In this study, the effects of various printing parameters (extrusion temperature, layer height and width, printing speed, and the number of conductive layers) on the electrochemical performance of PLA/CB electrodes fabricated via FDM were investigated. Electrochemical impedance spectroscopy analyses showed that properly adjusting these parameters promoted the formation of more efficient conductive pathways and reduced charge transfer resistance during monitoring of the redox behavior of the potassium ferrocyanide/ferricyanide probe. Furthermore, the electrochemical performance of the device was demonstrated through the detection of different model analytes, including dopamine, catechol, hydroquinone, paracetamol, and uric acid. The device was also applied to the determination of dopamine, achieving a detection limit of 0.16 µmol L⁻¹. Overall, the results highlighted that optimizing printing conditions is essential for improving the electrochemical performance of 3D-printed devices, reinforcing the potential of 3D printing as a promising route for the fabrication of electrodes for electroanalytical applications. Full article

In response to the requirements of wellbore plugging and lost circulation control, this study designed and prepared a new type of thixotropic polymer gel system. The optimal formula was obtained through systematic screening of the types and concentrations of high molecular polymers, cross-linking agents, flow pattern regulators, and resin curing agents. Comprehensive characterization of the gel’s gelling performance, thixotropic properties, high-temperature stability, shear resistance, and plugging capacity was conducted using methods such as the Sydansk bottle test, rheological testing, high-temperature aging experiments, plugging performance evaluation, as well as infrared spectroscopy, nuclear magnetic resonance, and thermogravimetric analysis, and its mechanism of action was revealed. The results show that the optimal formula is 1.2% AM-AA-AMPS terpolymer + 0.5% hydroquinone + 0.6% S-Trioxane + 0.8% modified montmorillonite + 14% modified phenolic resin. This gel system has a gelling time of 6 h, a gel strength reaching grade H, and a storage modulus of 62 Pa. It exhibits significant shear thinning characteristics in the shear rate range of 0.1~1000 s⁻¹, with a viscosity recovery rate of 97.7% and a thixotropic recovery rate of 90% after shearing. It forms a complete gel at a high temperature of 160 °C, with a dehydration rate of only 8.5% and a storage modulus retention rate of 80% after aging at 140 °C for 7 days. Under water flooding conditions at 120 °C, the converted pressure-bearing capacity per 100 m reaches 24.0 MPa. Mechanism analysis confirms that the system forms a stable composite network through the synergistic effect of “covalent cross-linking—hydrogen bonding—physical adsorption”, providing a high-performance material solution for wellbore plugging in high-temperature and high-salt environments. Full article

Hydroquinone is a phenolic compound widely used in industry and cosmetics, yet its toxicity has raised global environmental and health concerns. It has been listed by both the US EPA and the European Union as a priority contaminant for monitoring in aquatic systems. In this proof-of-concept (PoC) study, silver nanowires (Ag-NWs) were synthesized via a modified one-pot polyol methodology and characterized by various techniques, including TEM, EDX, SEM, XRD, and UV–vis spectroscopy. The Ag-NWs exhibited peroxidase-like activity, catalyzing the oxidation of TMB/H₂O₂ to yield a blue product. This activity was effectively suppressed by hydroquinone, forming the basis of a simple colorimetric sensing approach. The PoC method showed linearity over 0.08–0.8 µg/mL with a LOD of 26 ng/mL. Furthermore, it was preliminarily applied to tap water, river water, and medicated cream samples, demonstrating acceptable recovery in preliminary applications. As a PoC, the study establishes the feasibility of the Ag-NWs–TMB–H₂O₂ system for hydroquinone detection, while recognizing that comprehensive reproducibility assessment and temporal stability evaluation are required in future work. Full article

Quinone/hydroquinone couples play a crucial role in a variety of biochemical processes and chemical syntheses. Extending from our previous work, a practical dataset including the thermodynamic driving forces of 12 chemical processes for 118 quinone/hydroquinone couples accepting or releasing two hydrogen atoms in DMSO is established. The dataset serves as a foundation for assessing and discussing the thermodynamic capabilities of hydroquinones acting as two-hydrogen-atoms antioxidants or radical quenchers, quinones and semiquinone radicals acting as hydrogen atoms abstractors, and quinone/hydroquinone couples acting as dehydrogenation and hydrogenation reagents. The fundamental thermodynamic knowledge is expected to further promote the broader application of quinone/hydroquinone couples in the field of chemical antioxidation and redox reactions. Full article