Search Results (135)

The reaction of either the L or D enantiomer of H₂N-C*H(R)CO₂⁻ (R = -CH₂SH cysteine, C; -C(SH)(CH₃)₂, penicillamine, PN; or -CH₂CH₂SH, homocysteine, HC) with an imidazole-4-carboxaldehyde and nickel(II) acetate in methanol yields a single stereoisomer of a thiazolidine (from C or PN) or a thiazine (from HC) nickel complex. Five pairs of enantiomeric products were prepared and characterized by IR, ESI MS, EA, and single crystal structure determination. There is retention of chirality for the thiazolidine and thiazine complexes on ring position 4, C_α of the parent amino acid, and transfer of chirality to the newly generated stereogenic centers, ring positions 3 (the amino acid nitrogen atom, N_AA) and 2 (the aldehyde carbon atom, C_ald). For the thiazolidines, the new stereogenic centers, N_AA, and C_ald, have identical stereochemical assignments to one another and to the assignment of the alpha carbon atom, either all R from the L enantiomers of C and PN or all S from the D enantiomers of C and PN. For the thiazine products from HC, the newly generated stereogenic centers, ring positions 3 (N_AA) and 2 (C_ald), are identical to one another but opposite to that of the retained stereogenic center (ring position 4, the alpha carbon atom). Regardless of stereochemical assignment (R or S), the hydrogen atoms of C_α, N_AA, and C_ald, ring positions 4, 3, and 2, are always all cis to one another for the five pairs of enantiomers examined. This is a consequence of the fact that the thiazolidine and thiazine rings are fused to two other chelate rings of the complexes, which seems to explain the high stereospecificity observed in these systems. Full article

Developing cost-effective alternatives to platinum-based catalysts remains paramount for commercializing anion exchange membrane fuel cells (AEMFCs). We report a metal-free nitrogen-doped carbon catalyst derived from a rationally designed polyurea–polyimine copolymer that outperforms commercial 20 wt% Pt/C in superior relative durability and methanol tolerance. Strategic integration of polyurea’s pore-forming capability with polyimine’s thermal stability enabled the synthesis of a catalyst (NC-1000N) featuring ultrahigh surface area (1276.5 m² g⁻¹), optimal nitrogen speciation (20.5% pyridinic-N, 45.3% graphitic-N), and enhanced graphitization, which improves the electrical conductivity of catalysts. NC-1000N exhibited exceptional oxygen reduction performance with an onset potential of 0.96 V, almost four-electron selectivity (n = 3.87), a medium Tafel slope (105 mV dec⁻¹), and minimal charge transfer resistance (46.74 Ω). When evaluated in single-cell AEMFCs, NC-1000N delivered a peak power density of 372.1 mW cm⁻², which is 26% higher than Pt/C at equivalent loading, while demonstrating superior stability (94.8% retention after 7 h) and complete methanol tolerance. Systematic pyrolysis temperature optimization (800–1000 °C) revealed critical structure–property relationships governing catalyst evolution from disordered precursor to highly graphitic, nitrogen-enriched carbon with precisely engineered active sites. This work establishes polymer-derived carbons and provides design principles for scalable synthesis of high-performance metal-free electrocatalysts for sustainable energy conversion technologies. Full article

Background: Oxidative stress contributes significantly to premature skin aging and inflammatory dermatological conditions. While plant-derived antioxidants have demonstrated considerable promise in topical applications, Bougainvillea glabra Choisy remains underexplored in standardized pharmaceutical dosage form development despite its documented phytochemical richness. Objective: This study aimed to develop, standardize, and characterize topical cold cream formulations incorporating B. glabra ethanolic leaf extract, with HPTLC-based quantification of marker compounds, validated antioxidant assessment, and preliminary dermal safety evaluation. Methods: The ethanolic leaf extract was prepared by maceration and characterized by preliminary phytochemical screening and HPTLC fingerprinting with quantitative densitometric analysis of quercetin and pinitol. Three cold cream formulations were developed at 10% (F1), 20% (F2), and 30% (w/w) (F3) extract loading. Formulations were evaluated for organoleptic properties, pH, homogeneity, spreadability, and viscosity. Antioxidant activity was assessed using a validated methanol extraction procedure followed by DPPH radical scavenging and potassium permanganate reduction assays. Ex vivo skin permeation was evaluated using Franz diffusion cells with freshly excised goat skin. Accelerated stability was conducted at 40 ± 2 °C/75 ± 5% RH for 90 days with HPTLC-based marker retention monitoring. Primary dermal safety was assessed in Wistar albino rats (n = 6) following OECD Test Guideline 404. Results: Quantitative HPTLC confirmed quercetin (4.82 ± 0.14 mg/g dry extract) and pinitol (2.31 ± 0.09 mg/g) as marker compounds, with linearly increasing content across F1–F3. All formulations demonstrated acceptable physicochemical properties (pH 5.7–5.9, viscosity 440,000–460,000 cP, spreadability 11.8 ± 0.3 cm·g/s). F3 exhibited the highest DPPH scavenging activity (56.68 ± 1.05%) with IC₅₀ of 1.3 ± 0.1% w/v, demonstrating a 3.2-fold improvement over F1. Extraction recovery from the cream matrix was 96.4–97.1%, validating the antioxidant data. Ex vivo quercetin permeation through goat skin reached 51.3 ± 2.8 μg/cm² at 24 h for F3, following Higuchi diffusion kinetics (R² > 0.99). No dermal irritation was observed (Primary Irritation Index = 0). Accelerated stability confirmed ≥98.3% retention of both marker compounds and antioxidant activity after 90 days. Conclusions: B. glabra leaf extract was successfully incorporated into a physicochemically stable, non-irritating cold cream with demonstrated dose-dependent antioxidant efficacy and cutaneous delivery capability. The study establishes preliminary dermal safety and in vitro antioxidant efficacy warranting further controlled clinical evaluation. Full article

Ginkgo biloba seeds are a rich source of flavonoids and the unique terpene lactones—ginkgolides and bilobalide, known for their neuroprotective and cognitive-improving effects. However, unlike the widely used leaves, the seeds contain substantial levels of ginkgolic acid and ginkgotoxin (4′-O-methylpyridoxine), an antivitamin B₆ compound. At high concentrations, ginkgotoxin exhibits neurotoxicity, potentially inducing seizures, respiratory distress, and loss of consciousness, thus limiting the safe application of Ginkgo seed-derived products. This study aimed to develop a simple yet effective extraction protocol that reduces ginkgotoxin levels in Ginkgo biloba seed extracts while preserving their beneficial phytochemicals. A multistep liquid–liquid extraction approach employing sequential polar and non-polar solvents was implemented. Following each extraction stage, fractions were analyzed using ultra-high-performance liquid chromatography coupled with mass spectrometry (UHPLC–MS). The concentrations of flavonoids, ginkgolides, bilobalide, ginkgolic acid, and ginkgotoxin were quantified to evaluate detoxification efficiency and phytochemical retention. Compared with conventional single-step extraction using 70% methanol, this multistep protocol markedly reduced ginkgotoxin and ginkgolic acid to near-undetectable levels, while preserving detectable concentrations of major flavonoids and terpene trilactones. The findings demonstrate that multistep extraction represents a promising and practical strategy for minimizing ginkgotoxin in Ginkgo biloba seed extracts without compromising their beneficial phytochemical composition. This approach provides a sound basis for developing safer, functionally active Ginkgo-based products. Full article

The present study aimed to establish a robustness modeling framework for the determination of cannabidiol (CBD) and Δ⁹-tetrahydrocannabinol (THC) in cannabis extract using a multivariate approach. A two-level full factorial design was implemented to examine four critical analytical factors, including methanol concentration (80–85% v/v), flow rate (0.8–1.2 mL/min), column temperature (23–27 °C), and detection wavelength (208–212 nm). Seven analytical responses for each compound were assessed, including peak area, retention time, resolution, asymmetry factor, number of theoretical plates, capacity factor, and peak area difference relative to the reference method. Statistical analysis demonstrated that both main effects and interaction effects significantly influenced the measured responses. Design space construction was performed based on predefined acceptance criteria to ensure method robustness: resolution > 1.5, asymmetry < 1.5, number of theoretical plates > 2000, capacity factor > 2, and peak area difference within −5% to 5%. Predictive performance of the developed models was verified by comparing predicted and experimental results. Good agreement was observed under most conditions, whereas deviation was noted for THC quantification at a detection wavelength of 212 nm. Furthermore, CBD and THC contents determined under three selected operating conditions within the established design space were statistically comparable to those obtained using the reference method, except for the condition employing 212 nm detection. The Analytical GREEnness Metric Approach (AGREE) assessment indicated moderate greenness performance of the analytical procedure. Overall, the multivariate two-level full factorial design proved to be an effective tool for robustness modeling of the HPLC method for simultaneous quantification of CBD and THC. Full article

The functional valorization of waste fabrics, particularly their conversion into flexible low-cost, high-performance electrodes, holds significant promise for resource sustainability and the development of advanced energy technologies. Here, a NiB/Cu/polyester fabric (PF) composite electrode was fabricated via two-step electroless plating on waste PF and was demonstrated as a bifunctional electrocatalyst for methanol oxidation (MOR) and urea oxidation (UOR). The morphology, crystal structure, surface chemical state, and wettability of the electrodes were characterized using SEM, TEM, XRD, XPS, and contact angle measurements. The Cu interlayer critically enhanced interfacial wettability, intrinsic catalytic activity and stability. At 0.8 V, the NiB/Cu/PF electrode delivered average current densities of 312 mA·cm⁻² for MOR and 288 mA·cm⁻² for UOR, outperforming NiB/PF by 27.9% and 9.1%, respectively. After 2000 accelerated degradation cycles with electrolyte renewal, MOR and UOR activities were retained at 91.6% and 105.0%, respectively. Remarkably, the Cu interlayer conferred exceptional mechanical–electrochemical robustness: following 100 sequential bending and twisting deformations, current density retention ranged from 84.6% to 96.7% across multiple test configurations. The Cu interlayer acted as a flexible stress buffer during mechanical deformation, effectively improving the adhesion between the coating and the substrate. Full article

Aim: The aim of this study was to develop and validate a reliable HS-GC-FID/FID method for the determination of ethanol and other low-molecular-weight volatile compounds in biological fluids for forensic applications. Method: The method is based on headspace gas chromatography with dual-column and dual flame ionization detection (HS-GC-FID/FID), using Zebron ZB-BAC1 and ZB-BAC2 columns. The procedure was validated in terms of linearity, limits of detection and quantification, precision, and accuracy, as well as carryover. Results: The method demonstrated linearity over the concentration range of 0.05–5.0‰, with R² values of 0.997–0.999. The limit of quantification (LOQ) was 0.05‰, and the limit of detection (LOD) was 0.025‰. Precision and accuracy were both below 5%. Retention times (min) on the two columns were as follows: methanol (1.70/1.81), ethanol (2.06/2.29), acetone (2.60/2.59), isopropanol (2.45/2.73), n-propanol (3.24/3.98), and n-butanol (6.35/8.45). The developed method was successfully evaluated through international proficiency testing and is routinely applied in our laboratory for forensic casework. Conclusions: The developed HS-GC-FID/FID method provides accurate and reliable determination of ethanol and other relevant volatile compounds in biological fluids (i.a., blood) and meets the requirements for forensic toxicology. Additionally, the literature review conducted in this study highlights that globally unified principles for forensic alcohol analysis are still lacking, and that certain inappropriate methodological approaches remain in use. The present paper also provides recommendations defining essential methodological requirements to ensure the evidential reliability of ethanol analysis in forensic toxicology. Full article

This study presents a headset-type biofluorometric gas sensor incorporating a CMOS camera for continuous, non-invasive monitoring of transcutaneous ethanol from the ear canal. The sensor employs alcohol dehydrogenase (ADH) to catalyze the NAD⁺-to-NADH conversion during ethanol oxidation, enabling quantitative measurement through NADH fluorescence detection (λ_ex = 340 nm, λ_em = 490 nm). The integrated system comprises a wireless CMOS camera, an ADH-immobilized cotton mesh enzyme membrane, UV-LED excitation source, optical bandpass filters, and a dual convex lens assembly housed in a 3D-printed headset powered by a lithium battery. Key improvements include a 3.5-fold enhancement in fluorescence collection efficiency achieved through optimized dual convex lens configuration. Systematic screening of seven cotton mesh materials identified Iwatsuki cotton mesh as the optimal enzyme immobilization substrate, exhibiting minimal autofluorescence and 14.2-fold higher water retention capacity compared to H-PTFE membranes. The glutaraldehyde-crosslinked ADH-immobilized cotton mesh maintained enzymatic activity for over 45 min with a 10-fold improvement in signal-to-noise ratio. The system demonstrated a dynamic detection range spanning 10 ppb to 10 ppm for gaseous ethanol and exhibited high selectivity against interfering volatile organic compounds in skin gas, including methanol, acetaldehyde, formaldehyde, and acetone. Human experiments validated the system’s practical performance. Following alcohol consumption, subjects wore the device for 50 min while real-time fluorescence monitoring captured dynamic ethanol concentration changes in the ear canal. The dose-dependent fluorescence response—approximately 2-fold higher at 0.4 g/kg versus 0.04 g/kg alcohol intake—correlated well with calibration data. This headset-type biofluorometric sensor enables unrestrained continuous monitoring of ear canal ethanol, providing a novel wearable platform for alcohol metabolism assessment with potential applications in health monitoring and clinical research. Full article

The aim of this work was to evaluate the compositional, functional, antioxidant, thermal, and structural properties of faba bean flour (FBF) and a faba bean protein concentrate (FBC) elaborated by a sustainable dry fractionation method. Proximate composition was determined by analyzing the content of moisture, protein, lipids, ash, total dietary fiber, starch, and available carbohydrates. A methanolic extract was used to analyze total polyphenols and antioxidant capacity using complementary methods. The fatty acid profile was determined by gas chromatography. Techno-functional properties were assayed, determining water-holding capacity (WHC), oil absorption capacity (OAC), and retention capacity of different solvents (SRC), water activity, pH, and titratable acidity. Structural and thermal properties were studied by FTIR and DSC. The dry method produces a concentrate with a low quantity of starch (2.5 vs. 25.6%) and carbohydrates and higher amounts of proteins (61.14 vs. 23.61%). Lipids, mainly mono and polyunsaturated ones, and polyphenols with high antioxidant activity. FBC absorbed a greater proportion of lactic acid, likely due to its higher acidity, and showed higher oil absorption, but retained less water compared to FBF. FTIR and DSC results suggested that the heat-treated proteins (in FBC) exhibited some degree of protein denaturation, unlike the FBF proteins. These findings highlight the potential of dry-fractionated faba bean concentrate as a sustainable and functional food ingredient, particularly for products aimed at improving nutritional quality. Its enhanced antioxidant profile, favorable lipid composition and unique techno-functional properties make it a promising alternative for developing plant-based foods. Full article

MXene, as a suitable and alternative 2D nanofiller incorporated into a proton exchange membrane (PEM), has recently received considerable attention because of desired mechanical stability, promising conductivity, and active surface functional groups. However, agglomeration or sedimentation in PEMs, as well as the water retention capacity under low humidity of MXene, are limiting factors in the field of PEMs. In this paper, modified MXene and TiO₂ nanoparticles used as functional nanofillers were incorporated into sulfonated poly (ether ether ketone) (SPEEK) to prepare novel SPEEK-based composite PEMs. The effects of the nanofiller contents on self-humidifying and protonic conductivity of the composite PEMs were also investigated under different temperatures. When the contents of functionalized MXene and modified TiO₂ are 5 wt.%, proton conductivity, water uptake and methanol permeability of the composite PEMs can be up to 0.143 S/cm, 60% and 2.27 × 10⁻⁷ cm²/s, respectively, which represent increases of about 192%, about 38% and a decrease of 47%, respectively, compared with that of primary SPEEK PEM. Under the synergistic action of functionalized MXene providing a higher number of exchangeable proton sites, modified TiO₂ with inherent hydrophilicity enhancing water retention and Pt providing catalytic sites for the H₂/O₂ reaction to generate water in situ, the self-humidifying capability and proton conductivity of the composite PEMs were improved significantly. Full article

In this study, sixteen secondary metabolites, including two chromones, four dibenzofurans, three lipids, three depsides, two aromatic compounds, a quinone, and a terpene, were detected in the methanol:acetone (1:1 v/v) extract of the lichen Hypotrachyna enderythraea (Zahlbr.) Hale, using High-Performance Liquid Chromatography coupled to Orbitrap Electrospray Ionization tandem Mass Spectrometry (HPLC-Orbitrap ESI tandem MS/MS). These metabolites were characterized by analysis of their exact molecular masses and corresponding fragmentation patterns. The retention times of the identified metabolites were compared with those of standard compounds, confirming the presence of naturally occurring bioactive compounds. Density Functional Theory (DFT) calculations were employed to investigate preferential deprotonation sites in representative polyprotic metabolites. All these findings may contribute to expanding the spectrum of compounds identified within the genus Hypotrachyna and to evaluating their potential biological activities. Full article

Copper-based catalysts have emerged as promising materials for electrochemical carbon dioxide reduction reactions, owing to copper’s unique ability to facilitate multi-electron transfer processes and produce valuable products such as methanol and ethanol. In this study, novel trisferrocenyltrithiophosphite–copper(I) bromide composites with Cu-to-ligand molar ratios of 1:1 and 2:1 were synthesized and evaluated for their catalytic performance. The composites were characterized by a combination of techniques, including powder X-ray diffraction (PXRD), linear sweep voltammetry (LSV), potentiostatic testing, chromatographic analysis, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical measurements demonstrated significant current enhancements in the presence of CO₂, highlighting the composites’ catalytic activity. Potentiostatic tests revealed excellent stability, with only a 9% decline in current density over 5 h of electrolysis. Product analysis via gas chromatography indicated the formation of methanol for the 1:1 composite and ethanol for the 2:1 composite with Faradaic efficiencies of 5.79% and 9.26%, respectively. While absolute efficiencies remain modest due to competitive hydrogen evolution, these results demonstrate a tunable catalytic performance based on the Cu-to-ligand ratio. SEM and XPS studies further supported the formation of active catalytic centers and changes in the oxidation states of copper during CO₂ reduction. PXRD analysis confirmed the retention of structural integrity for both composites before and after catalytic testing. Full article

Municipal solid waste (MSW) recycling is constrained by contamination, heterogeneity, and infrastructure built around material-specific pathways. We introduce effectiveness-normalized greenhouse gas (GHG) emissions as a system-level metric that adjusts reported process burdens by feedstock eligibility (Effectiveness Fraction, EF) and carbon recovery efficiency (CRE) to reflect real-world MSW conditions. Using published LCA data and engineering estimates, we benchmark six pathways, mechanical recycling, PET depolymerization, enzymatic depolymerization, pyrolysis, supercritical water gasification (SCWG), and Regenerative Robust Gasification (RRG), at the scale of mixed MSW. Normalizing for EF and CRE reveals large differences between process-level and system-level performance. Mechanical recycling and PET depolymerization show low process intensities yet high normalized impacts because they can treat only a small share of plastics in MSW. SCWG performs well at broader eligibility. RRG, a plasma-assisted molten-bath approach integrated with methanol synthesis, maintains the lowest normalized impact (~1.6 t CO₂e per ton of recycled polymer) while accepting virtually all organics in MSW and vitrifying inorganics. Modeled methanol yields are ~200–300 gal·t⁻¹ without external hydrogen and up to ~800 gal·t⁻¹ with renewable methane reforming. The metric clarifies trade-offs for policy and investment by rewarding technologies that maximize diversion and carbon retention. We discuss how effectiveness-normalized results can be incorporated into LCA practice and Extended Producer Responsibility (EPR) frameworks and outline research needs in techno-economics, regional scalability, hydrogen sourcing, and uncertainty analysis. Findings support aligning infrastructure and procurement with robust, scalable routes that deliver circular manufacturing from heterogeneous MSW. Full article

Phlorotannin–alginate extracts from brown seaweeds offer promising natural solutions for food preservation. This study investigated the extraction, characterization, and application of phlorotannins and alginate from two brown seaweed species, Sargassum cristaefolium and Nizimuddinia zanardinii, for inhibiting melanosis and preserving quality in Pacific white shrimp during ice storage. Preliminary screening identified N. zanardinii methanol extract as superior, yielding the highest phlorotannin content (19.14 ± 0.65 mg Phloroglucinol/g) with potent antioxidant (98.95 ± 0.74% DPPH inhibition) and copper-chelating (73.44 ± 1.64%) activities. Consequently, N. zanardinii was selected for subsequent extraction and application studies. Alginate extraction efficiency was 4.73 ± 0.38 g/100 g seaweed, demonstrating moderate antioxidant properties. The extracts effectively inhibited shrimp polyphenol oxidase, with 2% phlorotannins + 1% alginate showing 84.51% inhibition. When applied to shrimp, this combination significantly delayed melanosis development, suppressed microbial growth, and maintained lower pH, total volatile basic nitrogen (TVB-N), and lipid oxidation values during 16 days of ice storage compared to untreated controls. Sensory evaluation confirmed better retention of quality attributes in treated shrimp. These findings demonstrate the potential of N. zanardinii phlorotannin–alginate extracts as effective natural preservatives for maintaining shrimp quality during cold storage, offering a sustainable alternative to synthetic additives in seafood processing. Full article

This study introduces nitrogen- and silicon-containing carbon quantum dots (N,Si-CQDs), synthesized hydrothermally from the sustainable bioresource stinging nettle (Urtica dioica L.), as chemically active supports for Pt, Pd, and Pt₃Pd₁ electrocatalysts. The N,Si-CQDs were characterized by a high concentration of N/O surface functionalities and the presence of biogenic Si. A significant finding is that, with this support, biogenic Si acts as a nucleation template: Pd forms in situ as orthorhombic Pd₉Si₂ nanorods alongside spherical particles, whereas Pt predominantly develops as cubic/quasi-cubic crystals. This templating process promotes faceted (cubic) Pt₃Pd₁ alloy nanoparticles with robust interfacial contact with the support and a log-normal size distribution (14.2 ± 4.3 nm) on N,Si-CQDs (4.7 ± 1.4 nm). This configuration enhanced the electrochemically active surface area to 181 m² gPt⁻¹, significantly exceeding those of commercial Pt₁Pd₁/XC-72 (27.7 m² gPt⁻¹) and monometallic Pt/N,Si-CQDs (14.3 m² gPt⁻¹). Consequently, the catalyst demonstrated superior methanol oxidation performance, evidenced by a low onset potential (0.17 V), approximately 10-fold higher mass activity compared to Pt₁Pd₁/XC-72, and 53% activity retention after a 16 h accelerated durability test. The enhanced performance is attributed to the strong nanoparticle anchoring by N,Si-CQDs, the bifunctional/ligand effects of the Pt–Pd alloy that improve CO tolerance, and the templating role of biogenic Si. Full article