Search Results (220)

We report here a thorough study concerning the acylation reaction products of 8-hydroxyquinoline with 2-chloroacyl chloride, with new insights and clarifications in respect to the obtained products brought by NMR and X-ray studies. According to the reaction conditions we employed, three compounds could be obtained: 1-(2-chloro-2-oxoethyl)pyridin-1-ium chloride 10, 8-hydroxyquinoline hydrochloride 11, and the acylated product 8-(2-chloroacetoxy)quinolin-1-ium chloride 12. A certain influence of the catalyst and the used solvent was observed, and feasible explanations for product formations were furnished. The structure of the compounds was proved by using ¹H- and ¹³C-NMR spectra as well as single-crystal X-ray diffraction studies for compounds 12 and 11. According to X-ray crystallography, compounds 11 and 12 have a planar structure and exhibit an ionic crystal structure crystallized as a hydrochloride salt of the corresponding organic base. The crystal structures of both compounds are stabilized by intermolecular hydrogen bonds and π-π stacking interactions. In the crystals of compounds 11 and 12, the structural components are interconnected by a system of intermolecular hydrogen bonding, and a similar one-dimensional array is formed via hydrogen bonding and π-π stacking. The further assembling of the structure for 12 and 11 occurs with the formation of a three-dimensional supramolecular network. Full article

Zinc(II) bis(8-hydroxyquinolinate) (Zn(HQ)₂) and 1,10-phenanthroline (phen) were combined to fabricate an organic semiconductor in a bulk heterojunction architecture and subsequently embedded in a poly 3,4-ethylene dioxythiophene–polystyrene sulfonate (PEDOT–PSS) matrix. The resulting Zn(HQ)₂-phen/PEDOT–PSS was deposited as a film upon tin-oxide-coated glass and graphite-covered Tetra Pak (TP)-recycled substrates for the manufacture of organic photoconductive devices. The topographical and micromechanical characteristics of the hybrid films were assessed by atomic force microscopy, with an average roughness of 5.6 nm, maximum tensile strength of 7.95 MPa, and Knoop microhardness of 14.7. The fundamental energy gap (E_g) was determined employing the Kubelka–Munk function, with E_g of 3.5–3.8 eV. These results were complemented with a computational DFT molecular orbital analysis of the species involved in the hybrid semiconductor. The devices were electrically characterized under UV irradiation conditions, obtaining the current–voltage and power–voltage relationships. The maximum current in the TP–graphite device is 1.8 × 10⁻² A and 1.1 × 10⁻² A in the device on glass–ITO. Zn(HQ)₂-phen/PEDOT–PSS film presents its own operating regimes relating to a photoconductor or flexible photoresistor. The power in the device on glass–ITO is 120 mW and 113 mW for shortwave and longwave, respectively, and in the device on TP–graphite, it is 198 mW and 139 mW. Full article

Background: 8-Hydroxyquinoline and phthalimide are two significant heterocyclic scaffolds in medicinal chemistry due to their pharmacological profiles. Hybridizing these pharmacophores and further modifying them via modified Mannich reactions provides a strategy to improve their physicochemical parameters and selectivity toward multidrug-resistant (MDR) cancer cells. Objectives: To synthesize a series of 8-hydroxyquinoline–phthalimide hybrids and their Mannich base derivatives and evaluate their cytotoxic activity and resistance-selective properties against sensitive Colo205 and resistant Colo320 cancer cell lines. Methods: Four hybrid compounds were synthesized by reacting 5-amino-8-hydroxyquinoline with different phthalic anhydride derivatives. Twelve fine-tuned derivatives were prepared by using the modified Mannich reaction. Cytotoxic activity was measured using the MTT assay, and relative resistance (RR) was calculated to determine selectivity toward the resistant cell line. P-glycoprotein (Pgp) ATPase activity was evaluated for the most active compounds. Results: All derivatives displayed cytotoxic activity, with higher potency toward the resistant Colo320 cell line. Compounds 2 and 4 showed the strongest activity against both cell lines (IC₅₀ down to 4.88 µM). Compounds 5, 8a, 9a, and 9c retained potent activity against Colo320 (IC₅₀ = 9.89–22.79 µM). Incorporating a CH₂–N group at position C7 substantially enhanced the selectivity for MDR cells. Compounds 9c, 9a, and 8a exhibited the highest selectivity, with RR values of 0.29, 0.33, and 0.35, respectively. Compounds 2, 4, 5, 8a, and 9a showed inhibitory effects on Pgp ATPase activity. Conclusions: The newly synthesized HQ–phthalimide hybrids represent promising candidates for targeting MDR in colorectal cancer, with Mannich modification enhancing the selectivity toward resistant cells. Full article

Cut flowers of Matthiola incana ‘Mera’ are widely used in floristics but because of wilting, premature leaf yellowing, and flower/inflorescence drying their ornamental value quickly drops. The postharvest performance of this valuable cut flower in terms of symptoms of wilting, relative water content (RWC), carbohydrate content, enzyme activity, and free proline content was studied in relation to the different preservative added to the vases with flowers. The tested preservatives were based on two biocides: 200 mg/L 8-hydroxyquinoline citrate (8-HQC) and nanosilver (NS) in two concentrations, 1 and 5 mg/L, with the addition of 2% sucrose (S). Control inflorescences were kept in distilled water alone. The above preservatives did not prolong vase life, but, on the contrary, decreased it, so flowers placed in distilled water lasted the longest. The contents of both total soluble and reducing sugars increased during flower senescence, reaching the highest level in flowers held in the solution of 5 mg/L NS plus 2% S. Similarly, the content of free proline increased, especially in flowers held in the 8-HQC with 2% S (standard preservative). The contents of hydrogen peroxide (H₂O₂) varied in flowers from different solutions; however, they kept increasing during senescence in flowers from all the treatments. The highest activity of the antioxidative enzymes was found in flowers placed in water. Full article

In this paper, three quinoline-based quaternary ammonium salts were successfully synthesized, with quinoline, 8-hydroxyquinoline, and 8-methoxyquinoline used as raw materials, and benzyl chloride as a quaternization reagent. The as-synthesized quaternary ammonium salts showed excellent corrosion inhibition performance in the acidic environment based on the derivative’s cationic activity, heteroatom electron effect, and conjugated aromatic system. Specifically, the methoxy-containing product exhibited the highest corrosion inhibition efficiency of 96.92%. The quantitative calculation analysis demonstrated that the addition of methoxy and hydroxyl groups facilitated the quaternization reaction and enhanced the adsorption of the quaternary ammonium salts on the metal surface. The molecular dynamics study indicated that the three corrosion inhibitors adsorbed on the metal surface in a parallel orientation. This study has a certain reference significance for the research and development of quaternary ammonium salt as corrosion inhibitors in an acidic environment. Full article

Organoboron compounds have attracted significant interest because of their special properties conferring photoluminescence, electroluminescence, and chemiluminescence. However, there are few reported examples of their use in electrochemiluminescence (ECL). This work represents a significant contribution by providing comprehensive evidence that elucidates the critical role of four-coordinate boron coordination in modulating and enhancing ECL properties. By introducing a coordinatively saturated boron center into a designed molecular framework, we achieved a 2.5-fold enhancement in ECL intensity during electrochemical processes. These results address the limited fundamental understanding of ECL behavior pertinent to tetracoordinate boron systems and provide valuable insights into molecular design strategies for developing stable and highly efficient ECL luminophores. Full article

Understanding how solvents influence the luminescence behavior of Cu(I) complexes is crucial for designing advanced optical sensors. This study reports the synthesis, structures and photophysical investigation of an 8-hydroxyquinoline-functionalized 1H-imidazo[4,5-f][1,10]phenanthroline ligand, ipqH₂, and its four Cu(I) complexes with diphosphine co-ligands. Photoluminescence studies demonstrated distinct solvent-dependent excited-state mechanisms. In DMSO/alcohol mixtures, free ipqH₂ exhibited excited-state proton transfer (ESPT) and enol-keto tautomerization, producing dual emission at about 447 and 560 nm, while the complexes resisted ESPT due to hydrogen bond blocking by PF₆⁻ anions and Cu(I) coordination. In DMSO/H₂O, aggregation-caused quenching (ACQ) and high-energy O–H vibrational quenching dominated, but complexes 1 and 2 showed a significant red-shifted emission (569–574 nm) with high water content due to solvent-stabilized intra-ligand charge transfer and metal-to-ligand charge transfer ((IL+ML)CT) states. In DMSO/DMF, hydrogen bond competition and solvation-shell reorganization led to distinct responses: complexes 1 and 3, with flexible bis[(2-diphenylphosphino)phenyl]ether (POP) ligands, displayed peak splitting and (IL + ML)CT redshift emission (501 ⟶ 530 nm), whereas complexes 2 and 4, with rigid 9,9-dimethyl-4,5-bis(diphenylphosphino)-9H-xanthene (xantphos), showed weaker responses. The flexibility of the diphosphine ligand dictated DMF sensitivity, while the coordination, the hydrogen bonds between PF₆⁻ anions and ipqH₂, and water solubility governed the alcohol/water responses. This work elucidates the multifaceted solvent-responsive mechanisms in Cu(I) complexes, facilitating the design of solvent-discriminative luminescent sensors. Full article

Invasive fungal infections and the emergence of antifungal resistance pose significant challenges to public health. This study evaluates the antifungal activity of two 8-hydroxyquinoline derivatives, PH265 and PH276, against Cryptococcus spp., Candida auris, and Candida haemulonii. Using the EUCAST protocol, both compounds demonstrated broad-spectrum antifungal activity, with MICs ranging from 0.5 to 8 μg/mL. PH276 exhibited synergistic effects with fluconazole and caspofungin against C. haemulonii (FIC ≤ 0.5). The derivatives inhibited C. neoformans biofilm formation at higher concentrations and modulated polysaccharide capsule formation in Cryptococcus spp. In vivo toxicity assays in Tenebrio molitor, Galleria mellonella, and Caenorhabditis elegans revealed no significant adverse effects, with survival rates comparable to controls. These findings highlight PH265 and PH276 as promising antifungal agents with biofilm-disrupting properties, capsule-modulating effects, and low toxicity, supporting their potential for therapeutic development. Full article

A novel quinoline-containing benzoxazine resin, 8HQ-fa, has been successfully synthesized at room temperature using sustainable raw materials, such as 8-hydroxyquinoline and furfurylamine as the phenol and amine source, respectively. The chemical structure of the hereinafter referred to as quinolinoxazine is fully characterized by Fourier transform infrared spectroscopy (FT-IR), ¹H and ¹³C nuclear magnetic resonance spectroscopy (NMR), as well as by 2D ¹H–¹H nuclear Overhauser effect spectroscopy (NOESY) and ¹H–¹³C heteronuclear multiple quantum correlation (HMQC) NMR. Thermal properties and polymerization behavior of the monomer are studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The resulting polymer is also characterized in terms of its thermal and fire-related properties by DSC, TGA, and microscale combustion calorimetry (MCC). The resulting thermoset, poly(8HQ-fa), presents good thermal stability as evidenced by its T_g (201 °C), T_d5 and T_d10 (307 and 351 °C, respectively), and char yield (42%), and low flammability as determined by the LOI, heat release capacity, and total heat released values (34.3, 143 J/gK, and 10.8 kJ/g, respectively), making it a self-extinguishing thermoset. The combination of properties and advantages in the synthesis of 8HQ-fa, accompanied by a low polymerization temperature, suggests its great potential in the field of high-performance polymers. Full article

This work describes a simple and economical electrochemical route for the generation of mesoporous alumina (MA) particles that can serve as containers for corrosion inhibitors for the active corrosion protection elements of metals when dispersed in organic coatings. The synthesis of precursor slurries was carried out in an electrochemical reactor with aluminum electrodes operating alternately as anodes and cathodes to facilitate metal dissolution and prevent passivation of the electrode surface. The obtained slurries were thermally treated to produce mesoporous alumina particles with adsorbent characteristics suitable for loading corrosion inhibitors. Benzotriazole (BTA) and 8-hydroxyquinoline (8HQ) were chosen as corrosion inhibitors. Dispersed in a commercial polymer matrix and applied to the coating of mild steel samples, the loaded MA improved the corrosion resistance of the coated metal exposed to a simulated marine environment. When physical damage is intentionally caused to expose the underlying metal, the polymer matrix containing BTA-loaded alumina particles retards the corrosion process due to the swelling of the inhibitor from the particles to the exposed bare metal in the scratch. Electrochemical impedance spectroscopy (EIS) measurements showed a marked increase in low-frequency impedance in coatings containing alumina particles, with the BTA-loaded system providing the most durable protection over extended immersion times (with a 50% improvement in corrosion resistance of steel exposed within the scratch). This demonstrates the potential of this approach for long-term corrosion protection applications. Full article

Biocatalytic nanomembranes have emerged as promising platforms for micropollutant remediation, yet their practical application is hindered by limitations in removal efficiency and operational stability. This study presents an innovative approach for fabricating highly stable and efficient biocatalytic nanomembranes through the co-immobilization of horseradish peroxidase (HRP) and glucose oxidase (GOx) within a covalent organic framework (COF) nanocrystal. Capitalizing on the dynamic covalent chemistry of COFs during their self-healing and self-crystallization processes, we achieved simultaneous enzyme immobilization and framework formation. This unique confinement strategy preserved enzymatic activity while significantly enhancing stability. HRP/GOx@COF biocatalytic membrane was prepared through the loading of immobilized enzymes (HRP/GOx@COF) onto a macroporous polymeric substrate membrane pre-coated with a polydopamine (PDA) adhesive layer. At HRP and GOx dosages of 4 mg and 4.5 mg, respectively, and a glucose concentration of 5 mM, the removal rate of bisphenol A (BPA) reached 99% through the combined functions of catalysis, adsorption, and rejection. The BPA removal rate of the biocatalytic membrane remained high under both acidic and alkaline conditions. Additionally, the removal rate of dyes with different properties exceeded 88%. The removal efficiencies of doxycycline hydrochloride, 2,4-dichlorophenol, and 8-hydroxyquinoline surpassed 95%. In this study, the enzyme was confined in the ordered and stable COF, which endowed the biocatalytic membrane with good stability and reusability over multiple batch cycles. Full article

Aromatic hydrazones of 7-hydrazino-8-hydroxyquinoline were studied as anti-HIV and antibacterial compounds. A set of the compounds with different aromatic moieties bearing electron-donating and electron-withdrawing substituents has been selected and obtained via the hydrazo coupling and “one-pot” click reaction with aldehydes. The compounds possess activity against both bacterial and fungal targets. Cellular Ku70-inhibiting activity has been found for the series, opening a new class of inhibitors for potential anti-HIV treatment. The compounds display anti-HIV activity in infected cells at submicromolar concentrations. Their low solubility can be overcome by incorporation in water-soluble neutral polyalginate microgels (33% wt load of the compound). Full article

A novel series of multifunctional tacrine–quinoline hybrids were designed, synthesized, and evaluated as potential anti-Alzheimer’s agents. These compounds incorporate tacrine for cholinesterase’s inhibition and 8-hydroxyquinoline for metal chelation. Piperazine was selected as a linker to provide conformational flexibility and to create favorable cation–π interactions with residues in the mid-gorge region of AChE, enhancing dual-site binding with AChE to inhibit Aβ aggregation. In vitro studies demonstrated submicromolar inhibitory activity toward both AChE and BuChE, particularly for compounds 16e (IC₅₀ = 0.10 μM for AChE, 0.043 μM for BuChE) and 16h (IC₅₀ = 0.21 μM for AChE, 0.10 μM for BuChE). These compounds also exhibited potent inhibition of self-induced Aβ_1–42 aggregation (16e: 80.5% ± 4.4%, 16h: 93.2% ± 3.9% at 20 μM). Kinetic analyses revealed mixed-type inhibition, suggesting dual binding to both CAS and PAS of AChE. UV–vis spectrometry confirmed the chelation of Cu²⁺ and Zn²⁺ ions by the 8-hydroxyquinoline moiety. These findings highlight the tacrine–quinoline scaffold as a promising platform for the discovery of a multitarget-directed anti-AD drug. Full article

Background and Clinical Significance: Many women use pessaries to manage their symptoms of pelvic organ prolapse. Hydroxyquinoline is the active ingredient in gels and ointments that are often used to lubricate a pessary prior to vaginal insertion and to provide antimicrobial effects while the pessary is in situ. Case Presentation: A 74-year-old woman with multiple medication allergies develops vulvovaginal erythema and pruritus after increasing vaginal Trimo-San application frequency for pessary care and maintenance. These symptoms are deemed to be consistent with an allergic reaction to hydroxyquinoline, the active ingredient in Trimo-San. Conclusions: This report highlights the importance of personalized treatment in pessary management. It also demonstrates how personalized medicine can optimize outcomes and improve treatment adherence among individuals with complex medical histories. Full article

Background/Objectives: Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, remains a major neglected tropical disease, with over six million cases concentrated, primarily in Latin America. Despite decades of research, treatment continues to rely on two outdated drugs—benznidazole and nifurtimox—both of which exhibit limited efficacy and are associated with severe side effects. In this context, drug repurposing presents a promising strategy to accelerate the development of safer and more effective therapies. Nitroxoline, a hydroxyquinoline compound widely used in Europe to treat bacterial urinary tract infections, has recently garnered attention for its broad-spectrum antimicrobial and anticancer activities. This study evaluated the antitrypanosomal potential of nitroxoline against both epimastigote and intracellular amastigote forms of T. cruzi, demonstrating significantly greater efficacy than benznidazole. Methods: In addition to its antiparasitic activity, we investigated the mechanism of parasite death and found that nitroxoline induces hallmarks of programmed cell death, including chromatin condensation, mitochondrial membrane depolarization, ATP depletion, reactive oxygen species accumulation, and increased membrane permeability. These cellular events are critical for minimizing host tissue inflammation and suggest a safer therapeutic profile. Results: The nitroxoline was shown to induce greater activity than the reference treatment, benznidazole, in addition to triggering events related to apoptotic or silent cell death. Conclusions: Given its established clinical use and favorable safety data, nitroxoline emerges as a strong candidate for further investigation as a repurposed treatment for Chagas disease. Future work should focus on in vivo efficacy, pharmacokinetics, and drug delivery strategies to enhance systemic bioavailability. Full article