Compounds

For cable compound manufacturers, accurate formulation fine-tuning is essential to ensure safety, long-term durability, and compliance with international standards for dielectric strength, volume resistivity, and environmental and thermal ageing. This work presents an experimental study demonstrating how minor additives can critically affect the performance of complex flame-retardant elastomeric formulations. The investigation focuses on the role of small amounts of zinc oxide (ZnO) in commercial cable compounds based on a crosslinked elastomeric matrix composed of ethylene–propylene monomer (EPM), ethylene–propylene–diene monomer (EPDM), and thermoplastic polyolefin elastomer (POE). The formulations contain aluminium trihydroxide (ATH) as the major filler, together with several minor additives. Among these, a phenolic antioxidant (AN01) acting as a metal deactivator is also present. The addition of ZnO in low amounts (2–5 phr) allowed the compounds to maintain a volume resistivity ≥ 10¹² Ω·cm in water at 100 °C. To elucidate the role of ZnO, a systematic set of formulations was prepared by varying the type and content of selected additives. The compounds were prepared by melt mixing in an internal mixer (Banbury type), followed by peroxide crosslinking via compression molding. Electrical characterization results indicate that ZnO interacts with the phenolic additive through surface adsorption, forming a coated particle with significantly reduced electrical conductivity. Optimal electrical performance was achieved when the ZnO-to-additive ratio corresponded to the minimum amount required for complete surface complexation. Full article

Nalca (Gunnera tinctoria Mol.) is traditionally consumed for its edible petioles and valued for medicinal properties associated with its bioactive compounds. In this study, natural deep eutectic solvents (NADESs) were synthesized and applied for the ultrasound-assisted extraction of phenolic compounds and alkaloids from Nalca leaves. NADES synthesis was confirmed using ¹H NMR, and their physicochemical properties were evaluated to assess their influence on extraction efficiency. The extracts showed total phenolic contents ranging from 6.8 to 142.6 mg GAE/g DW and total alkaloid contents ranging from 0.2 to 3.2 mg OXIE/g DW, depending on solvent composition. Antioxidant activity, evaluated using DPPH and FRAP assays, confirmed that most NADES extracts exhibited significant radical-scavenging and ferric-reducing capacities, generally correlating with phenolic content. The extraction yields obtained with specific NADES formulations were comparable or superior to those achieved with conventional solvents, demonstrating their efficiency. These results demonstrate that NADESs are effective and environmentally friendly alternatives to conventional solvents for extracting bioactive compounds from Nalca leaves. The physicochemical properties of NADESs enable the selective extraction of different metabolite classes, highlighting their potential for green extraction processes in food, nutraceutical, and pharmaceutical applications. Full article

The growing demand for healthier meat products has led to efforts to reduce synthetic additives, such as nitrites, in processed meats. This study evaluated the effect of enriched safflower oil with oleoresin from Capsicum annuum var. Anaheim (ESO) as a functional ingredient in the reformulation of Frankfurt-style pork sausages with reduced nitrite content. Five formulations were evaluated: a negative control without additives (F1 (0% ESO, 0% nitrite), a positive control containing only sodium nitrite F2 (0% ESO, 0.15% nitrite = 93.8 mg/kg), and three experimental treatments contained ESO and nitrite: F3 (0.5% ESO, 0.075% nitrite = 46.9 mg/kg), F4 (1% ESO, 0.05% nitrite = 31.3 mg/kg), and F5 (1.5% ESO, 0% nitrite), stored under refrigeration (4 °C) for five weeks. Physicochemical (pH, color, texture profile, proximate composition, residual chlorides and nitrites), oxidative (TBARS), and microbiological (total viable count) analyses were conducted over 5 weeks of storage. Results showed that formulation F4 provided the best balance between oxidative stability microbial control and nitrite residual content, maintaining TBARS levels below the 1.0 mg MDA/kg rancidity threshold (0.33 ± 0.01 mg MDA/kg), TVC within the 6.0 log CFU/g limit for processed meats (3.89 log CFU/g) and 1.15 mg/kg of nitrite residual at the end of the storage period. These findings suggest a synergistic effect between ESO and nitrites. Since addition of ESO was consistent with improved cured color development, likely due to the combined effect of reduced nitrite levels and the natural pigments from Anaheim chili. These findings demonstrate that ESO is a promising natural additive to partially replace nitrites, contributing to the development of healthier and safer processed meat alternatives. Full article

Antioxidants, such as phenolic compounds, are essential for mammal physiology. Significant research made on the gut–brain axis has produced volumes of evidence indicating that some plant-derived phenolic compounds can reach brain cells to exert protective effects on them, mainly by maintaining and/or restoring redox homeostasis. Their systemic uptake and transport might be determined by the phenolic’s physicochemical properties, along with complex interactions with protein transporters and carriers, including GLUT, SGLT1, ABC transporters (P-glycoprotein, breast cancer resistance protein), albumin, fibrinogen, organic anion and cation transporters, and MATE1. The present work focuses on the chemical interactions and transport pathways of some phenolic compounds to reach brain cells. Full article

A novel multidentate ligand with an O,N,O-tridentate ligand moiety and an N-heterocyclic carbene (NHC) was synthesized. Its palladium complex, in which the NHC part coordinates to the palladium atom, was synthesized and structurally characterized. The O,N,O-part coordinated to an early transition metal such as titanium. The Ti-Pd heterobimetallic complex was observed in solution. Full article

Mn and Fe complexes of ethylene cross-bridged tetraazamacrocycles, known to retain their reactive metal ions even under harsh aqueous conditions due to the rigidity and topological constraint of the ligands, with methyl, allyl and benzyl pendant arms were electrostatically fixed to a commercial cation exchange resin, and their effectiveness and recyclability in the bleaching of organic dyes, namely, methyl orange, methylene blue and rhodamine B, were determined. These molecular Mn and Fe tetraazamacrocycle catalysts have been previously reported as homogeneous solution phase catalysts for bleaching organic dyes, but could not be feasibly recovered for multiple cycles of dye bleaching. Herein, we report the potential of these resin-fixed solid-state metal complex catalysts in the degradation of organic dyes. The Mn catalysts were faster in the first cycle of dye bleaching, but their bleaching rate slowed considerably (to about 10% on average) in additional cycles. In contrast, the Fe catalysts were slower in the first cycle of dye bleaching, but were able to bleach dyes for up to five cycles while retaining more of their original reactivity (30–50% on average), suggesting their potential recyclability. Thus, these resin-fixed tetraazamacrocyclic metal complex catalysts, when coupled with the demonstrated rechargeability of the resin with fresh catalyst, may one day be effectively used for water purification applications. SEM and optical microscopy images demonstrated the robustness of the resin bead across multiple cycles, while EDS experiments confirmed the continued presence of Mn and Fe on the bead surface after multiple cycles. Full article

Background: Increasing antimicrobial resistance has directed studies toward investigating the antimicrobial activity of thymol, as well as the antibiofilm and antioxidant potential of its emulsions (with Tween 80) against multidrug-resistant (MDR) K. pneumoniae isolates. Methods: A microdilution assay was used to estimate thymol’s antibacterial potential against 10 clinical isolates (labeled 1–10). The dynamic light scattering technique was used to measure the particle size diameter (Zavg) of formulated emulsions. The antibiofilm potential of emulsions was assessed in vitro using a crystal violet assay and ex vivo on a surgical drain through a colony-forming unit assay. Antioxidant activity was screened by using the DPPH assay. Results: The MIC values were ≤1.5 mg/mL for strains 1 and 7 and <0.5 mg/mL for the other strains. Emulsions E_250:500, E_250:750, E_300:750, and E_500:750 were stable and homogeneous, with a Zavg of approx. 200 nm (128.4 ± 0.8 nm for E_250:750). These emulsions significantly reduced the biofilm biomass of strains 3 and 7 (50.6–74.32% and 34.60–59.8% of inhibition, respectively), with the strongest activity observed for E_250:500 and E_500:750. Antibiofilm potential was confirmed ex vivo, with E_500:750 showing the highest efficacy (ΔLogCFU 2.60 and 2.68 for strains 3 and 7). E_250:750 demonstrated the highest capacity to neutralize the DPPH• radical. Conclusions: Thymol and its emulsions exhibited antibacterial and antibiofilm activity against MDR K. pneumoniae isolates, along with the proven antioxidant properties of the emulsions. Full article

α-Fe_2−4xZ_3xO₃ (Z = Ce, Ru) nanoparticles were synthesized via a conventional solid-state reaction route. X-Ray diffraction analysis confirmed that all compositions crystallize in the single-phase hexagonal hematite (α-Fe₂O₃) structure, with no detectable secondary phases. Cerium substitution resulted in a pronounced reduction in crystallite size accompanied by a progressive narrowing of the optical band gap, which decreased to approximately 1.73 eV at higher Ce contents. The optical properties were further investigated through absorption coefficient, optical transmittance, and complex refractive index analyses, revealing that cerium-doped hematite exhibits enhanced light-harvesting capability, highlighting its strong potential for optoelectronic and solar-energy conversion applications. Magnetic hysteresis measurements on α-Fe_2−4xRu_3xO₃ samples showed a systematic increase in both coercive field (H_c) and remanent magnetization (M_r) with increasing Ru concentration. This magnetic hardening behavior is attributed to strengthened magnetocrystalline and shape anisotropy induced by Ru incorporation into the hematite lattice. Mössbauer spectroscopy confirmed the presence of Fe³⁺ and Ru⁴⁺ species, providing valuable insight into the oxidation states and local magnetic environments within the corundum-type structure. Full article

Biofouling, the formation of a biofilm on submerged surfaces, is a widespread problem affecting all of the maritime industries and ecosystems. Historically, antifouling solutions have included toxic compounds, such as heavy metals and tributyl tin. Recently, less-toxic antifouling paints have been explored, including paints made from antioxidant-rich plants, and a study measured the effectiveness of polymer blends containing Aronia mitschurinii extracts. This new study will compare those results with polymer blends made from extracts of juvenile ginger and holy basil, two plants rich in antioxidants and essential oils. Extracts were assessed for antioxidant and essential oil content. Then, slides coated with a polymer-extract blend were exposed to freshwater and saltwater for three weeks and assessed by contrast microscopy. For freshwater and saltwater analysis, holy basil extracts had a minimum precipitation count of 3.40 ± 0.4 and 22.4 ± 6.0 for non-stained slides and 58.3 ± 7.3 and 9.3 ± 1.0 for stained. Ginger extracts had a minimum precipitation count of 3.9 ± 0.8 and 87.1 ± 17.3 for non-stained slides, and 5.4 ± 1.8 and 9.5 ± 0.3 for stained slides. All minimum precipitation counts for ginger and holy basil were less than those measured by controls and Aronia mitschurinii, showcasing the antifouling potential of ginger and holy basil extracts at a compatible but slightly lower level, but one that is much higher than was reported for other plant materials. Full article

In recent years, Biophytum umbraculum Welw. (Oxalidaceae) has undergone several phytochemical and pharmacological investigations. Although its major phytochemical classes have been characterized, few isolated compounds have been reported. The previously detected phytoconstituents, along with the documented antioxidant and anti-inflammatory activities, both align with a potential antiproliferative effect. This study aims to complement the existing chemotaxonomic profile of B. umbraculum through the isolation and identification of phytoconstituents and to evaluate the antiproliferative potential of its extracts. Hexane, ethyl acetate, and methanolic extracts of B. umbraculum were screened against two human adherent cell lines, breast (MCF-7) and cervical (SiSo) adenocarcinomas, by using the crystal violet staining assay. The hexane extract inhibited both MCF-7 and SiSo cell proliferation with IC₅₀ values of 8.93 ± 0.07 and 14.59 ± 0.08 µg/mL, respectively. The ethyl acetate extract showed activity against both cell lines, with IC₅₀ values of 12.60 ± 0.14 and 13.10 ± 0.04 µg/mL, respectively. However, the methanolic extract was inactive on the MCF-7 cell line and only slightly active on the SiSo cell line. Chromatographic fractionations led to the isolation of ursolic acid from the active ethyl acetate extract and rutin from the methanolic extract. A further antiproliferative evaluation is warranted to confirm the contribution of ursolic acid to the effect of the ethyl acetate extract. Additional fractionations may uncover more phytoconstituents of diverse pharmaceutical interests. Full article

A systematic study of the chemoselectivity of the reduction of 3-methylcyclohex-2-enone (seudenone) to 3-methylcyclohex-2-enol (seudenol) was performed. Two approaches were investigated, namely the reduction of this ketone using NaBH₄ with modifiers and Catalytic Transfer Hydrogenation (CTH). The former resulted in higher conversions (95–99%) and high selectivity (up to 95%), whereas with CTH, a selectivity of 100% was achieved, albeit with a low conversion. The study therefore demonstrated that it is possible to chemoselectively reduce an α,β-unsaturated ketone in the liquid phase CTH using MgO as the catalyst and 2-pentanol as the hydrogen donor. The application of modifiers such as CeCl₃ · 7H₂O and MCl₂, where M = Be, Mg, Ca, Sr, and Ba, resulted in a significant improvement of the chemoselectivity (up to 95%) of the reduction with NaBH₄. The effect of parameters such as the solvent mixture composition, reaction temperature and modifier:NaBH₄ molar ratio was also investigated. In CTH, although high conversions of the ketone were observed for Al₂O₃, ZrO₂ and MgO in the vapor phase, the first two did not yield 3-methylcyclohex-2-enol among the obtained products. It was shown that 3-methylcyclohex-3-enol was the main product of the transformations of 3-methylcyclohex-2-enone in the presence of MgO, with yields of 25–33%. In a series of experiments, it was shown that 3-methylcyclohex-3-enol is formed as a result of the transformation of 3-methylcyclohex-2-enol in the presence of MgO as a catalyst. Full article

The growing demand for sustainable, functional food ingredients has increased interest in algae, particularly for their bioactive compounds. Gracilaria birdiae is mainly used for agar production, but its protein potential is underexplored. Conventional extraction methods require high temperatures and long durations, whereas emerging technologies, such as ultrasound (US), could be more efficient alternatives when combined with other strategies. This study is the first to evaluate the co-extraction of carbohydrates and proteins from G. birdiae using US combined with different extraction methods. The proximate composition of the algae was as follows: 63.97% carbohydrates, 5.20% proteins, and 19.65% lipids. Ethanol pretreatment did not improve US co-extraction but enabled phycobiliprotein recovery. Higher US power (500 W, 373 W·cm⁻²) and biomass concentration enhanced recovery, achieving up to 64.43 mg/g of carbohydrates and 10.28 mg/g of proteins. Sequential extraction using hot water and US at 60 °C produced 97.51 and 74.70 mg/g of carbohydrates and 5.67 and 5.08 mg/g of proteins, respectively. Acid treatment combined with US 60 °C achieved the highest recovery of 396.15 mg/g carbohydrate (1% v/v H₂SO₄) and 38.49 mg/g of protein (7% v/v H₂SO₄). Alkali extraction yielded lower amounts: 190.51 mg/g of carbohydrates and 33.20 mg/g of protein using 5% w/v NaOH. Microscopy revealed that the chemical treatments fully disrupted the cell wall, promoting compound release. Thus, combining the US with chemical extraction effectively enhances carbohydrates and protein recovery from G. birdiae. Full article

In this work, gellan gum microspheres (G–MPs) were developed as delivery systems for blueberry extract (Vaccinium myrtillus) (BEX), a source of natural antioxidants rich in anthocyanins (ATCs) and phenolic compounds (PHCs). Gellan gum, an anionic polysaccharide produced via fermentation by Sphingomonas elodea, was selected for its biocompatibility and gelling properties. BEX was obtained using a mild citric acid–based extraction method to preserve antioxidant capacity and was characterized for its total polyphenol, flavonoid, and anthocyanin content before loading. The extract was loaded into gellan gum microspheres via absorption (G–MPs–BEX). The resulting microspheres exhibited a spherical and porous morphology that favoured both encapsulation and controlled release. FT–IR analysis confirmed the absorption of the extract within the polymer network and revealed hydrogen bonding interactions between the matrix and active compounds. Despite these interactions, microspheres retained a high swelling capacity and enabled rapid release, with maximum release of polyphenols and anthocyanins within 30 min at pH 5.5. The antioxidant activity of BEX, assessed via DPPH assay, remained stable during storage (up to 60 days) and after incorporation into the microspheres. Overall, this study demonstrates that G–MPs can efficiently absorb, stabilize, and release natural antioxidant compounds, supporting their potential use in biomedical, nutraceutical, and cosmetic applications. Full article

This study evaluated the effects of incorporating silk fibroin nanoparticles into self-curing polymethyl methacrylate (PMMA) on the mechanical and Candida albicans responses of provisional dental prostheses. Rectangular specimens (64 × 10 × 3 mm) were fabricated and assigned to three groups (n = 10): G1 (control), PMMA without reinforcement; G2, PMMA with 0.5% silk nanoparticles; and G3, PMMA with 1% silk nanoparticleScheme4. 4 × 6 mm) were prepared. Scanning electron microscopy (SEM) was used to assess nanoparticle incorporation within the polymer matrix. No significant differences were observed in surface roughness (G1 = 0.4118 ± 0.100; G2 = 0.3245 ± 0.072; G3 = 0.3269 ± 0.076) or microhardness (G1 = 12.21 ± 0.351; G2 = 12.72 ± 0.213; G3 = 12.53 ± 0.177). Flexural strength differed significantly among the groups (p = 0.009), with higher values in nanoparticle-reinforced specimens (G1 = 79.142 ± 3.202; G2 = 87.089 ± 2.756; G3 = 92.412 ± 1.963). None of the tested concentrations exhibited antifungal activity against C. albicans. In conclusion, the incorporation of silk fibroin nanoparticles enhanced the flexural strength of self-curing PMMA without adversely affecting surface roughness or microhardness, although no antifungal effect was detected at the evaluated concentrations. Full article

The aim of this study was to evaluate, on a preliminary basis, the ability of multivariate techniques to predict the antioxidant activity of selected Stachys and Betonica species, based on chromatographic data. The methanol extracts of six Stachys species and ten Betonica species were analyzed using reversed-phase high-performance liquid chromatography (RP-HPLC) to obtain their chromatographic profiles. The phytochemical similarity of the samples was assessed using a selected chemometric method (principal component analysis (PCA) and hierarchical cluster analysis (HCA)). The antioxidant activity of the studied extracts (DPPH with 2,2-diphenyl-1-picrylhydrazyl reagent and FRAP—ferric reducing antioxidant power) was determined using a spectrophotometric technique. A multivariate PLS model was then used to predict the antioxidant activity of the methanolic extracts of Stachys and Betonica species based on their RP-HPLC fingerprints. The two obtained PLS models proved useful for predicting the biological activity of the tested extracts. High correlation coefficients (DPPH: R² = 0.9963; FRAP: R² = 0.9895) confirmed the reliability of the PLS prediction model. The results confirmed the effectiveness of combining qualitative and quantitative chromatographic fingerprinting methods with antioxidant activity testing and chemometric analysis, demonstrating that extracts from Stachys and Betonica are a rich source of bioactive substances with antioxidant properties. Full article

The natural durability of wood, determined primarily by its chemistry, meets the growing demand for environmentally sustainable alternatives to toxic wood preservatives. This study assessed the relationship between the fungitoxic acetone extractive content, in particular resin acids and stilbenes, and heartwood decay resistance among fifty-two Pinus nigra J. F. Arnold clones from a clonal seed orchard in Greece. Quantitative ¹H-NMR spectroscopy was employed to determine total stilbenes (TSs) and total resin acids (TRAs) in heartwood samples, while decay resistance was evaluated through standardized weight loss tests using the brown-rot fungus Coniophora puteana (Schumach.) P. Karst. (1865) and the white-rot fungus Porodaedalea pini (Brot.) Murrill (1905). The heartwood exhibited exceptionally high extractive content (mean TAE = 304.15 mg g_dhw⁻¹), with resin acids (68.26%) predominating over stilbenes (22.31%). Regression analysis showed that the TAE and TRAs were the strongest predictors of decay resistance, explaining 33% of the variance, while stilbenes exhibited weaker and more variable associations. P. pini caused significantly higher mean weight loss (11.43%) than C. puteana (3.55%), indicating species-specific fungal aggressiveness. Among individual resin acids, abietic acids were the most influential contributors to decay resistance. The results demonstrate that resin acids have a dominant role over stilbenes in determining the natural durability of P. nigra (Black pine) heartwood and could serve as effective biochemical markers for selective breeding. Full article

Terpyridines are well-known ligands in coordination chemistry, are valued for their conformational flexibility and strong metal-binding properties, and are also of interest as fluorophores. This study focused on the synthesis and comprehensive investigation of a new class of bis-oxazolo[5,4-b]pyridine derivatives, designed based on their structural similarity to terpyridines. Four novel compounds, 4a–d, were synthesized by cyclization of amide derivatives of 3-aminopyridin-2(1H)-ones using pyridine-2,6-dicarboxylic acid and its dichloride as key acidic components. Their structures and purity were confirmed by melting point analysis, high-resolution mass spectrometry, and ¹H, ¹³C NMR spectroscopy. Compounds 4a–c exhibit UV absorption at 323–357 nm and intense blue to deep-blue fluorescence (357–474 nm, цi ≈ 0.32–0.84) in chloroform, dichloromethane, and acetonitrile, attributed to p–p* transitions within the conjugated ring system. These findings suggest their potential as phosphors for organic electronics. Computational modeling of 4a–c molecules provided insight into their electronic structures, conformational stability, and predicted optical behavior. The most stable conformers (4a–II, 4b–II, 4c–II′) exhibited a progressive decrease in the HOMO–LUMO gap from 4a to 4c, correlated with the enhancement of photoactivity. Among them, compound 4a stands out as the most promising luminophore, displaying the most intense and narrow luminescence band, owing to its high molecular symmetry and stable emission characteristics. Overall, this study lays the foundation for future studies of bis(oxazolo[5,4-b]pyridine) derivatives in coordination chemistry and optoelectronic materials development. Full article

Two crystalline complexes, (2,2′-bipyridine)Cu(CH₃COO)₂·5H₂O (3) and (2,2′-bipyridine)Cu(CH₃COO)₂·CH₃CN (4), have been isolated and characterized by low-temperature single-crystal X-ray diffraction experiments. Crystals of phase 3 were studied previously at room temperature (296 K) under conditions leading to rapid desolvation and less distinct characterization of the waters of crystallization. With our redetermination of 3 at 100(2) K, we present a detailed description of ribbon-like structure formed by water molecules in crystals of (2,2′-bipyridine)Cu(CH₃COO)₂·5H₂O. Acetate oxygens are linked by hydrogen-bonding to two inequivalent waters separated by 4.72 Å; the other three water molecules are trapped in polymeric ribbons of anticooperative hydrogen-bonded six-membered rings fused with cooperative hydrogen-bonded four-rings. Water oxygens of the fused ring ribbons associate only with other water oxygens, and this water structure has a local density and pair distribution function which resembles that of liquid water. Crystals of 4 are monoclinic, with acetonitrile of solvation unassociated with the complex. In both 3 and 4, bipyridine planes interleave through π-aryl stacking. Full article

Propolis is a resinous material produced by honeybees characterized by a high phenolic compound and flavonoid content. To date, several studies have examined the chemical composition of Mexican propolis from the south and north of the country. However, limited information is available on the chemical profile of propolis from central Mexico. The present study isolated six known compounds from propolis from central Mexico: one diterpene (sugiol, found for the first time in Mexican propolis), three flavonoids (chrysin, galangin 3-methyl ether, and 3,7-dimethoxyquercetin), a fatty acid (cerotic acid), and an unusual glycerol derivative (batyl alcohol). Moreover, LC-ESI-MS analysis conducted on the ethanolic extract led to the identification of three phenolic compounds and fourteen flavonoids commonly found in propolis. Lastly, the cytotoxic activity evaluation carried out on the ethanolic extract showed a decrease in the cell viability of human leukemia (Jurkat) cells in a concentration-dependent manner. Full article