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A new luminescent hybrid material was developed based on silica aerogel and a boron-containing coordination compound with 8-hydroxyquilinone. Its physicochemical and spectral-luminescent characteristics were investigated. A procedure eliminating the need for an expensive preliminary synthesis of a high-purity organoelemental boron-containing phosphor was developed for synthesizing the hybrid luminescent material. Hydrophobization of the aerogel was found to significantly increase the stability of the luminescent characteristics of the hybrid material. [ABSTRACT FROM AUTHOR]

A new series of tin(II) complexes (1, 2, 4, and 5) were successfully synthesized by employing hydroxy functionalized pyridine ligands, specifically 2-hydroxypyridine (hpH), 8-hydroxyquinoline (hqH), and 10-hydroxybenzo[h]quinoline (hbqH) as stabilizing ligands. Complexes [Sn(μ-κ2ON-OC5H4N)(N{SiMe3}2)]2 (1) and [Sn4(μ-κ2ON-OC5H4N)6(κ1O-OC5H4N)2] (2) are the first structurally characterized examples of tin(II) oxypyridinato complexes exhibiting {Sn2(OCN)2} heterocyclic cores. As part of our study, 1H DOSY NMR experiments were undertaken using an external calibration curve (ECC) approach, with temperature-independent normalized diffusion coefficients, to determine the nature of oligomerisation of 2 in solution. An experimentally determined diffusion coefficient (298 K) of 6.87 × 10−10 m2 s−1 corresponds to a hydrodynamic radius of Ca. 4.95 Å. This is consistent with the observation of an averaged hydrodynamic radii and equilibria between dimeric [Sn{hp}2]2 and tetrameric [Sn{hp}2]4 species at 298 K. Testing this hypothesis, 1H DOSY NMR experiments were undertaken at regular intervals between 298 K–348 K and show a clear change in the calculated hydrodynamic radii form 4.95 Å (298 K) to 4.35 Å (348 K) consistent with a tetramer ⇄ dimer equilibria which lies towards the dimeric species at higher temperatures. Using these data, thermodynamic parameters for the equilibrium (ΔH° = 70.4 (±9.22) kJ mol−1, ΔS° = 259 (±29.5) J K−1 mol−1 and ΔG°298 = −6.97 (±12.7) kJ mol−1) were calculated. In the course of our studies, the Sn(II) oxo cluster, [Sn6(m3-O)6(OR)4:{Sn(II)(OR)2}2] (3) (R = C5H4N) was serendipitously isolated, and its molecular structure was determined by single-crystal X-ray diffraction analysis. However, attempts to characterise the complex by multinuclear NMR spectroscopy were thwarted by solubility issues, and attempts to synthesise 3 on a larger scale were unsuccessful. In contrast to the oligomeric structures observed for 1 and 2, single-crystal X-ray diffraction studies unambiguously establish the monomeric 4-coordinate solid-state structures of [Sn(κ2ON-OC9H6N)2)] (4) and [Sn(κ2ON-OC13H8N)2)] (5). [ABSTRACT FROM AUTHOR]

In this work, we report on an approach to the description of acid–base equilibria of 8-hydroxyquinoline-modified silica gels, influencing both the effect of the double layer and competing processes at the interface. The samples were synthesized by the Mannich reaction. The surface density of the grafted groups was determined. The curves of acid–base titration of the modified silica gels were received by us and have been converted to charge density pH-dependent curves. These curves were used to carry out the fitting procedure. The ionic equilibria of surface groups, processes of interaction of surface groups with each other and the Diffuse Double Layer Model, considering the molecular and ionic forms on the surface, were used to describe protolytic equilibria. Within the applied model, the behavior of counterions in the surface layer and the surface equilibrium constants were assessed. The ionic equilibria of protolithic groups constants values were close to the ionization constants of homogeneous analogs. [ABSTRACT FROM AUTHOR]

The emerging antibiotic-resistant bacteria, especially the "ESKAPE" pathogens, pose a continuous threat to global health. In this study, we explored metalloantibiotics as promising therapeutics and innovative antimicrobial agents. The role of metal in the antimicrobial activity of chloroxine (5,7-dichloro-8-hydroxyquinoline), as a metalloantibiotic, was investigated by minimal inhibit concentration (MIC) assay and a series of assays, including growth curve, time-killing, and UV-visible spectroscopy and PAR (4-(2-pyridylazo)-resorcinol) competition assays. Both chloroxine and its structural analogues exhibited increased antibacterial potency against Gram-positive bacteria compared to Gram-negative bacteria. The introduction of exogenous manganese or zinc ions significantly boosted chloroxine's antibacterial efficacy against Gram-negative bacteria, including the notorious ESKAPE pathogens. However, the enhanced antibacterial activity induced by zinc ions could be negated in the presence of copper or ferrous iron ions, as well as changes in oxygen availability, highlighting the involvement of proton motive force, oxidative and antioxidative systems. Notably, chloroxine effectively inhibited the enzymatic activity of superoxide dismutase (SOD). In addition, chloroxine could reverse polymyxin and carbapenem resistance in E. coli in vitro. Therefore, these results suggested that chloroxine with zinc ions are promising therapeutics and antibiotics potentiator to combat multidrug-resistant ESKAPE pathogens., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

In this study, we investigated the abilities of nitrogen and sulfur heterocyclic carbenes of benzotriazole, 2-mercaptobenzothiazole, 8-hydroxyquinoline, and 3-amino-1,2,4-triazole-5-thiol regarding adsorption on an Al-Mg-Si alloy toward corrosion inhibition of the surface. Al-Si(14), Al-Si(19), and Al-Si(21) in the Al-Mg-Si alloy surface with the highest fluctuation in the shielding tensors of the “NMR” spectrum generated by intra-atomic interaction directed us to the most influence in the neighbor atoms generated by interatomic reactions of N → Al, O → Al, and S → Al through the coating and adsorbing process of Langmuir adsorption. The values of various thermodynamic properties and dipole moments of benzotriazole, 2-mercaptobenzothiazole, 8-hydroxyquinoline, and 3-amino-1,2,4-triazole-5-thiol adsorbed on the Al-Mg-Si increased by enhancing the molecular weight of these compounds as well as the charge distribution between organic compounds (electron donor) and the alloy surface (electron acceptor). Finally, this research can build up our knowledge of the electronic structure, relative stability, and surface bonding of various metal alloy surfaces, metal-doped alloy nanosheets, and other dependent mechanisms such as heterogeneous catalysis, friction lubrication, and biological systems.

The metal chelator PBT2 (5,7-dichloro-2-[(dimethylamino)methyl]-8-hydroxyquinoline) acts as a terdentate ligand capable of forming binary and ternary Cu2+ complexes. It was clinically trialed as an Alzheimer’s disease (AD) therapy but failed to progress beyond phase II. The β-amyloid (Aβ) peptide associated with AD was recently concluded to form a unique Cu(Aβ) complex that is inaccessible to PBT2. Herein, it is shown that the species ascribed to this binary Cu(Aβ) complex in fact corresponds to ternary Cu(PBT2)NImAβ complexes formed by the anchoring of Cu(PBT2) on imine nitrogen (NIm) donors of His side chains. The primary site of ternary complex formation is His6, with a conditional stepwise formation constant at pH 7.4 (Kc [M−1]) of logKc = 6.4 ± 0.1, and a second site is supplied by His13 or His14 (logKc = 4.4 ± 0.1). The stability of Cu(PBT2)NImH13/14 is comparable with that of the simplest Cu(PBT2)NIm complexes involving the NIm coordination of free imidazole (logKc = 4.22 ± 0.09) and histamine (logKc = 4.00 ± 0.05). The 100-fold larger formation constant for Cu(PBT2)NImH6 indicates that outer-sphere ligand–peptide interactions strongly stabilize its structure. Despite the relatively high stability of Cu(PBT2)NImH6, PBT2 is a promiscuous chelator capable of forming a ternary Cu(PBT2)NIm complex with any ligand containing an NIm donor. These ligands include histamine, L-His, and ubiquitous His side chains of peptides and proteins in the extracellular milieu, whose combined effect should outweigh that of a single Cu(PBT2)NImH6 complex regardless of its stability. We therefore conclude that PBT2 is capable of accessing Cu(Aβ) complexes with high stability but low specificity. The results have implications for future AD therapeutic strategies and understanding the role of PBT2 in the bulk transport of transition metal ions. Given the repurposing of PBT2 as a drug for breaking antibiotic resistance, ternary Cu(PBT2)NIm and analogous Zn(PBT2)NIm complexes may be relevant to its antimicrobial properties.

Chlamydia trachomatis causes the most common sexually transmitted bacterial infection and trachoma, an eye infection. Untreated infections can lead to sequelae, such as infertility and ectopic pregnancy in women and blindness. We previously enhanced the antichlamydial activity of the fluoroquinolone ciprofloxacin by grafting a metal chelating moiety onto it. In the present study, we pursued this pharmacomodulation and obtained nanomolar active molecules (EC50) against this pathogen. This gain in activity prompted us to evaluate the antibacterial activity of this family of molecules against other pathogenic bacteria, such as Neisseria gonorrhoeae and bacteria from the ESKAPE group. The results show that the novel molecules have selectively improved activity against C. trachomatis and demonstrate how the antichlamydial effect of fluoroquinolones can be enhanced. [ABSTRACT FROM AUTHOR]

In this work, we carried out the evaluation of the toxicity, the anxiogenic effect and the antidepressant activity by intraperitoneal administration of the compound "5-(((2-hydroxy-ethyl)thio)methyl)quinolin-8-ol)quinoline-8-ol." The anxiogenic effect was achieved by simple and effective texts already described in the literature such as open field test and elevated plus-maze test, while the antidepressant activity was carried out by performing the forced swimming test. To carry out this study, we have chosen, therefore, to use five groups of adult rats and each group contains five rats. The results obtained from this study show that this new compound derivative of 8-hydroxyquinoline does not show signs of toxicity, anxiety and depression before the lethal dose of 100 mg/kg (LD50 = 100 mg/kg), and by consequently, this compound is likely to present very important biological activity for a possible pharmaceutical and medicinal use at low doses (< 100 mg/kg). [ABSTRACT FROM AUTHOR]

Novel Schiff Base (E)-2-((4-chloro-3-nitrophenylimino)(phenyl)methyl)-5-methoxyphenol (S1) synthesized by condensing 2-hydroxy-4-methoxy benzophenone and 4-chloro-3-nitroaniline in ethanol and used for synthesis of five new mixed ligand complexes of Mn(II) Fe(III), Co(II), Ni(II), and Cu(II). The synthesized Schiff base ligand (S1) has been characterized by IR, UV–Visible, 1H-NMR, 13C-NMR spectra and all the synthesized complexes were characterized by elemental analysis, IR, electronic, thermal methods (TGA-DTA), Powder XRD analysis, magnetic susceptibility and molar conductivity measurements. All the complexes were proposed to have octahedral geometry. All the synthesized compounds were screened for their antimicrobial, antidibetic, antioxidant, antimalarial and anticancer activity. The obtained results indicated towards potential of these complexes as antimalarial and antioxidant agents. [ABSTRACT FROM AUTHOR]

• The formation and properties of a Charge transfer complex (CTC) between 8-Hydroxyquinoline (8HQ) and Quinol (Q) in different solvent polarities. • CT complex formation, instrumental analyses (FTIR, UV–visible spectroscopy, TGA/DTA, biological, computational, and SEM). • The FTIR confirmation of CTC formation, electronic spectra indicating charge transfer, physical composition, thermal behavior, surface characteristics, and biological activities. • DFT/TD-DFT and molECULAR DOCking Studies offer insights into energy, stability, molecular orbitals,. • CTC's electron transfer properties, with a focus on binding interactions with human serum albumin (HSA) for potential protein binding applications. The formation and characterization of a charge transfer complex (CTC) between 8-Hydroxyquinoline and Benzene-1,4-diol (Quinol) in various polar solvents. CTCs, marked by weak yet significant interactions, are pivotal in understanding electron transfer processes and molecular recognition phenomena. The choice of 8-Hydroxyquinoline (8HQ) as the donor and Quinol (Q) as the acceptor facilitates the investigation of their interaction, given their respective electron-rich and electron-poor properties. The spectroscopic analysis, including Fourier-transform infrared (FTIR) and UV-visible spectroscopy, reveals shifts in molecular vibrations and electronic transitions, indicating the formation of the CTC. Additionally, thermal analysis techniques, such as thermogravimetric analysis (TGA) and differential thermal analysis (DTA), provide insights into the thermal stability and decomposition behavior of the CTC. Powder X-ray diffraction (PXRD) analysis offers data on the crystalline structure and morphology of the complex. Furthermore, the manuscript explores the biological significance of the synthesized CTC, including its antioxidant, antibacterial, and antifungal activities. Conductivity measurements and computational studies, such as Density Functional Theory (DFT) and molecular docking, provide further insights into the electronic properties and structural characteristics of the CTC. Overall, the study contributes to advancing the understanding of CTCs and their applications, particularly in the context of novel donor-acceptor systems. The insights gained have implications in diverse fields, including materials science, biomedical engineering, and fundamental chemistry, paving the way for tailored molecular design and functional applications. [Display omitted] [ABSTRACT FROM AUTHOR]

A number of novel urea and thiourea derivatives of 8-hydroxyquinoline have been designed, synthesized and evaluated for their anticancer activities. The structures of the new compounds were established by spectroscopic techniques, 1H NMR, 13C NMR, and mass spectrometry. The in vitro cytotoxicity against MCF7, and MDA-MB-231 cell lines were assessed by MTT assay. Six of the 11 compounds synthesized namely 5b, 5c, 5f, and 6b-d exhibited cytotoxicity with IC50 values ranged between 0.5 and 42.4 µM. Apoptotic features of cells treated with 5b compound were observed via florescent microscopy using DAPI and ethidium bromide/acridine orange staining against MCF-7 cells. Molecular docking of these molecules against 16 potential breast cancer protein revealed that these compounds could interact with the active site of poly (ADP-ribose) polymerase-1 (PARP1), B-cell lymphoma-extra large (Bcl-xL) and PARP5A (Tankyrase 1) by forming hydrogen bonds, π-π interactions and hydrophobic interactions. The docked poses of these molecules were observed to be similar in the active site of each of these targets.

Developing a sufficient composite organic inhibitor coating on the surface of metals is a promising strategy to improve the protection capability of metal materials from corrosive media. In this study, dopamine is polymerized into a polydopamine coating on a copper surface by embedding 8-hydroxyquinoline (denoted as PDA@8-HQ). The formation mechanism of PDA@8-HQ on the surface of copper is confirmed by X-ray photoelectron spectroscopy, Fourier transform infrared reflectance, and Raman methods. Electrochemical and field emission scanning electron microscopic results show that the PDA@8-HQ coating made with the addition of 8-HQ was 0.02 M and had the greatest inhibition efficiency (99.1%). When the optimal composite coating is damaged by external forces, self-healing capability could be obviously found due to generating insoluble complex species between corrosive products of copper ions and 8-HQ and the salt solution in the damaged region. This study provides feasibility for the construction of functional corrosion inhibitors on the metal surface.

The antimicrobial properties of 8-Hydroxyquinoline (8-Hq), a small organic compound known for its metal-chelating capabilities, hold significant promise. However, its limited solubility in water poses a challenge for practical applications. In this study, we address this limitation by augmenting the antimicrobial efficacy of 8-Hq through its integration into the metal-organic framework UiO-66 (named 8-Hq@UiO-66) and coupling it with iron ions (designated as Fe/8-Hq@UiO-66) via an adsorption process. The sorption isotherm and adsorption kinetics were meticulously examined using Langmuir's adsorption model and the pseudo-second-order kinetic model. Material characterization techniques including powder X-ray powder diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, nitrogen adsorption isotherms, ultraviolet–visible spectroscopy, and photoluminescence spectroscopy revealed the coordination of zirconium clusters and iron with the nitrogen and hydroxyl groups of 8-Hq, respectively. Furthermore, our investigation into metal ion adsorption demonstrated that the 8-Hq@UiO-66 composite displayed a notable selectivity for iron ions over other metal ions in aqueous media. Under optimized conditions, the adsorption capacity for iron ions ranged from approximately 34–46 mg g−1. Importantly, the Fe/8-Hq@UiO-66 composite exhibited potent antimicrobial activity against Bacillus subtilis , Staphylococcus aureus , and Escherichia coli. These findings underscore the potential of incorporating 8-Hq into porous metal-organic frameworks and coupling it with iron ions to enhance its antimicrobial efficacy. [Display omitted] • Enhanced antimicrobial efficacy via 8-Hq and iron ion integration into UiO-66. • Insights from sorption isotherms and kinetics models. • Selective conjugation of iron ions by 8-Hq@UiO-66. • Potent antimicrobial activity against diverse bacterial strains demonstrated. [ABSTRACT FROM AUTHOR]

N-(3-(dimethylamino)propyl-4-(8-hydroxyquinolin-6-yl)benzamide (ML324, HL) is a potent inhibitor of the iron-containing histone demethylase KDM4, a recognized potential target of cancer therapeutics. Herein, we report the proton dissociation and complex formation processes of ML324 with essential metal ions such as Fe(II), Fe(III), Cu(II) and Zn(II) using UV–visible, fluorescence, electron paramagnetic resonance and 1H NMR spectroscopic methods. The electrochemical behaviour of the copper and iron complexes was characterized by cyclic voltammetry and spectroelectrochemistry. The solid phase structure of ML324 analysed by X-ray crystallography is also provided. Based on the solution equilibrium data, ML324 is present in solution in H 2 L+ form with a protonated dimethylammonium moiety at pH 7.4, and this (N,O) donor bearing ligand forms mono and bis complexes with all the studied metal ions and the tris-ligand species is also observed with Fe(III). At pH 7.4 the metal binding ability of ML324 follows the order: Fe(II) < Zn(II) < Cu(II) < Fe(III). Complexation with iron resulted in a negative redox potential (E ' 1/2 = −145 mV vs. NHE), further suggesting that the ligand has a preference for Fe(III) over Fe(II). ML324 was tested for its anticancer activity in chemosensitive and resistant human cancer cells overexpressing the efflux pump P-glycoprotein. ML324 exerted similar activity in all tested cells (IC 50 = 1.9–3.6 μM). Co-incubation and complexation of the compound with Cu(II) and Zn(II) had no impact on the cytotoxicity of ML324, whereas Fe(III) decreased the toxicity in a concentration-dependent manner, and this effect was more pronounced in the multidrug resistant cells. Synopsis The stability of the complexes of the histone demethylase inhibitor ML324 follows the order of Fe(II) < Zn(II) < Cu(II) < Fe(III) at pH 7.4. ML324 exhibits comparable cytotoxicity towards both drug-sensitive and drug-resistant cancer cells, and complexation with Fe(III) reduces cytotoxicity, particularly in resistant cells. [Display omitted] • Solution chemical properties of the histone demethylase inhibitor ML324. • Single crystal X-ray diffraction analysis on the solid structure of ML324. • Complexation of ML324 with endogenous metal ions, a special focus on iron(II). • Cytotoxicity on multidrug resistant human cancer cells affected by iron(III) ions. [ABSTRACT FROM AUTHOR]

Identifying potent bacterial algicidal agents is essential for the development of effective, safe, and economically viable algaecides. Challenges in isolating and purifying these substances from complex secretions have impeded progress in this field. Metabolomics profiling, an efficient strategy for identifying metabolites, was pioneered in identifying bacterial algicidal substances in this study. Extracellular secretions from different generations of the algicidal bacterium Brevibacillus sp. were isolated for comprehensive analysis. Specifically, a higher algicidal efficacy was observed in the secretion from Generation 3 (G3) of Brevibacillus sp. compared to Generation 1 (G1). Subsequent metabolomics profiling comparing G3 and 1 revealed 83 significantly up-regulated metabolites, of which 9 were identified as potential algicidal candidates. Back-validation highlighted the potency of 4-acetamidobutanoic acid (4-ABC) and 8-hydroxyquinoline (8-HQL), which exhibited robust algicidal activity with 3d-EC 50 values of 6.40 mg/L and 92.90 µg/L, respectively. These substances disrupted photosynthetic activity in M. aeruginosa by ceasing electron transfer in PSⅡ, like the impact exerted by Brevibacillus sp. secretion. These findings confirmed that 4-ABC and 8-HQL were the main algicidal components derived from Brevibacillus sp.. Thus, this study presents a streamlined strategy for identifying bacterial algicidal substances and unveils two novel and highly active algicidal substances. Harmful cyanobacterial blooms (HCBs) pose significant environmental problems and health effects to humans and other organisms. The increasing frequency of HCBs has emerged as a pressing global concern. Bacterial-derived algicidal substances are expected to serve as effective, safe, and economically viable algaecides against HCBs. This study presents a streamlined strategy for identifying bacterial algicidal substances and unveils two novel substances (4-ABC and 8-HQL). These two substances demonstrate remarkable algicidal activity and disrupt the photosynthetic system in M. aeruginosa. They hold potential as prospective algaecides for addressing HCBs. [Display omitted] • Metabolomics profiling was used to identify bacterial algicidal substances. • 4-ABC and 8-HQL were validated as effective algicidal substances. • 3 d-EC 50 values of 4-ABC and 8-HQL were 6.40 mg/L and 92.90 µg/L, respectively. • 4-ABC and 8-HQL both ceased electron transfer of PSⅡ in M. aeruginosa. [ABSTRACT FROM AUTHOR]

8-hydroxyquinoline (oxine) is a widely known and frequently used chelating agent, and the pharmacological effects of the core molecule and its derivatives have been studied since the 19th century. There are several synthetic methods to modify this core. The Mannich reaction is one of the most easily implementable examples, which requires mild reaction conditions and simple chemical reagents. The three components of the Mannich reaction are a primary or secondary amine, an aldehyde and a compound having a hydrogen with pronounced activity. In the modified Mannich reaction, naphthol or a nitrogen-containing naphthol analogue (e.g., 8-hydroxyquinoline) is utilised as the active hydrogen provider compound, thus affording the formation of aminoalkylated products. The amine component can be ammonia and primary or secondary amines. The aldehyde component is highly variable, including aliphatic and aromatic aldehydes. Based on the pharmacological relevance of aminomethylated 8-hydroxyquinolines, this review summarises their syntheses via the modified Mannich reaction starting from 8-hydroxyquinoline, formaldehyde and various amines.

In a “smart” corrosion-protective coating system, both the active anti-corrosion and the early corrosion detection of underlying metals are highly required. It is practical significant to develop materials that possess self-detecting of the early local corrosion and self-healing of coating defects simultaneously. The organic compound 8-hydroxyquinoline (8HQ) is an effective inhibitor and a fluorescent sensor probe for corrosion of aluminum alloy. Therefore, a layer double hydroxide (LDH) nanocontainer film loaded with the 8HQ was developed for the active corrosion protection purpose of aluminum alloy AA2024. In corrosive environments, the 8HQ are released from LDH film to inhibit the corrosion process, leading to the loss of the complexation with Al3+ ions in LDH laminates, thus turning off fluorescence. Results show that the LDH film loaded with 8HQ composites can improve the anti-corrosion performance of the film by releasing corrosion inhibitors on demand. Simultaneously, due to the complexation of 8HQ and Al3+ ions, the LDH film is fluorescent at the initial stage under ultraviolet light, and then becomes non-fluorescent at the corrosion sites, indicating the corrosion evolution process of the coating. The 8HQ-loaded LDH film with self-healing and self-detecting dual functions provides promising opportunities for the effective corrosion protection of aluminum alloy due to its “smart” and multifunctional properties.

We report the time-efficient synthesis of quinolin-8-yl 4-chlorobenzoate (3) via an O-acylation reaction between 8-hydroxyquinoline (1) and 4-chlorobenzoyl chloride (2) mediated by triethylamine in acetonitrile under heating at 80 °C for 20 min in the Monowave 50 reactor. This protocol is distinguished by its short reaction time, operational simplicity, and clean reaction profile. The structure of 3 was fully characterized through a combination of analytical techniques, including NMR, IR, and UV–Vis spectroscopy, MS spectrometry, differential scanning calorimetry (DSC), thermogravimetry (TG), and crystallographic studies. Interestingly, X-ray diffraction analyses of 3 show that the crystal structure is characterized by C-H···N, C-H···O, Cl···π, and π···π interactions. The molecular conformation presents an orthogonal orientation between aromatic rings in the solid state. The calculated interaction energies using the CE-B3LYP model show that dispersion forces act in a higher proportion to build the crystal, which is consistent with the few short hydrogen interactions detected. Electrostatic potential maps suggest the formation of σ-holes over the Cl atoms. Although they can behave as both Lewis acid and base sites, Cl··Cl interactions are absent due to the shallow depth of these σ-holes. Quantum chemical descriptors and global reactivity descriptors were examined using the B3LYP method with the 6-31G(d,p) basis set implemented in CrystalExplorer. Finally, compound 3 exhibited low activity against HOP-92 and EKVX non-Small-cell lung and UO-31 Renal cancer cell lines, with a growth inhibition percentage (GI%) ranging from 6.2% to 18.1%.

The fabrication of pH-sensitive lignin-based materials has received considerable attention in various fields, such as biomass refining, pharmaceuticals, and detecting techniques. However, the pH-sensitive mechanism of these materials is usually depending on the hydroxyl or carboxyl content in the lignin structure, which hinders the further development of these smart materials. Here, a pH-sensitive lignin-based polymer with a novel pH-sensitive mechanism was constructed by establishing ester bonds between lignin and the active molecular 8-hydroxyquinoline (8HQ). The structure of the produced pH-sensitive lignin-based polymer was comprehensively characterized. The substituted degree of 8HQ was tested up to 46.6% sensitivity, and the sustained release performance of 8HQ was confirmed by the dialysis method, the sensitivity of which was found to be 60 times slower compared with the physical mixed sample. Moreover, the obtained pH-sensitive lignin-based polymer showed an excellent pH sensitivity, and the released amount of 8HQ under an alkaline condition (pH = 8) was obviously higher than that under an acidic condition (pH = 3 and 5). This work provides a new paradigm for the high-value utilization of lignin and a theory guidance for the fabrication of novel pH-sensitive lignin-based polymers.

The increase of corrosion resistance of magnesium and its alloys by forming the smart self-healing hybrid coatings was achieved in this work in two steps. In the first step, using the plasma electrolytic oxidation (PEO) treatment, a ceramic-like bioactive coating was synthesized on the surface of biodegradable MA8 magnesium alloy. During the second step, the formed porous PEO layer was impregnated with a corrosion inhibitor 8-hydroxyquinoline (8-HQ) and bioresorbable polymer polycaprolactone (PCL) in different variations to enhance the protective properties of the coating. The composition, anticorrosion, and antifriction properties of the formed coatings were studied. 8-HQ allows controlling the rate of material degradation due to the self-healing effect of the smart coating. PCL treatment of the inhibitor-containing layer significantly improves the corrosion and wear resistance and retains an inhibitor in the pores of the PEO layer. It was revealed that the corrosion inhibitor incorporation method (including the number of steps, impregnation, and the type of solvent) significantly matters to the self-healing mechanism. The hybrid coatings obtained by a 1-step treatment in a dichloromethane solution containing 6 wt.% polycaprolactone and 15 g/L of 8-HQ are characterized by the best corrosion resistance. This coating demonstrates the lowest value of corrosion current density (3.02 × 10−7 A cm−2). The formation of the hybrid coating results in the corrosion rate decrease by 18 times (0.007 mm year−1) as compared to the blank PEO layer (0.128 mm year−1). An inhibitor efficiency was established to be 83.9%. The mechanism of corrosion protection of Mg alloy via smart hybrid coating was revealed.

Tannic acid (TA) as a natural plant polyphenol bearing multiple phenolic hydroxyl groups could cause considerable interactions with organic compounds. This work aims at detecting 8‐hydroxyquinoline (8‐HQ) based on poly (tannic acid) (PTA) by electropolymerization of TA on glassy carbon electrode (GCE). Owing to enhanced modified electrode surface area and interactions of PTA with 8‐HQ via hydrogen bonding and π‐π stacking, PTA/GCE exhibits electrocatalytic activity to 8‐HQ. Using Differential pulse voltammetry, PTA/GCE shows two linear plots with 8‐HQ concentrations from 0.5 to 5 μmol L−1 and 5 to 50 μmol L−1, the detection limit is 0.036 μmol L−1. The PTA modified electrode also shows great reproducibility and stability. The application of the sensor for real hair conditioner samples is demonstrated with satisfactory result. [ABSTRACT FROM AUTHOR]

The (±)‐, (+)‐ and (−)‐forms of 2‐amino‐3‐(8‐hydroxyquinolin‐3‐yl)‐propanoic acid (1 or 8HQ‐3Ala) have been prepared from o‐methoxyacetanilide (2). A combination of Vilsmeier‐Haack, Erlenmeyer‐Plöchl and methanolysis reactions was used to convert compound 2 into the Z‐configured dehydroamino acid derivative 5. Catalytic hydrogenation of the latter compound then gave, after reductive dechlorination and demethylation steps, compound (±)‐1. Asymmetric hydrogenation of compound 5 using a rhodium precatalyst and an enantiopure DuPhos‐type ligand selectively delivered either acid (+)‐1 or (−)‐1. The structure, including absolute configuration, of the latter product was confirmed through single‐crystal X‐ray analysis of the corresponding HBr mono salt. [ABSTRACT FROM AUTHOR]

Often associated to the colonization by Candida spp. biofilm, the catheter‐related infections are a serious health problem since the absence of a specific therapy. Hence, the main objective of this work was to evaluate the activity of 8‐hydroxyquinoline and quinazoline derivatives on Candida spp. biofilms. A quinazoline derivative (PH100) and an 8‐hydroxyquinoline derivative (PH157) were tested against nine strains of C. albicans, C. tropicalis and C. parapsilosis, and their biofilms in polystyrene microtitre plates and on polyurethane central venous catheter. The PH157 compound was incorporated into a film‐forming system‐type formulation and its capacity to inhibit biofilm formation on catheters was evaluated. The compounds were active against planktonic and sessile cells, as well as against the tested biofilms. PH157 compound performed better than the PH100 compound. The formulation containing PH157 presented results very similar to those of the compound in solution, which indicates that its activity was preserved. Both compounds showed activity against Candida spp. strains and their biofilm, with better PH157 activity. The formulation preserved the action of the PH157 compound, in addition, it facilitates its application on the catheter. The structural modifications that these compounds allow can generate compounds that are even more active, both against planktonic cells and biofilms. [ABSTRACT FROM AUTHOR]

A simple and efficient protocol for the synthesis of the previously unknown 2-(2-(4-methoxyphenyl)furo[3,2-h]quinolin-3-yl)acetic acid was elaborated. The suggested method is based on the telescoped multicomponent reaction of 8-hydroxyquinoline, 4-methylglyoxal, and Meldrum's acid. The studied process includes the initial interaction of the starting compounds in MeCN followed by intramolecular cyclization to the target product in refluxing acetic acid. The advantage of this approach is the application of readily available starting materials, atom economy, and a simple work-up procedure. The structure of the synthesized furylacetic acid derivative was proven by 1H, 13C, 2D-NMR, IR spectroscopy, and high-resolution mass spectrometry. [ABSTRACT FROM AUTHOR]

Density functional theory approaches are employed to elucidate the structural features and electronic properties of cis-dioxidomolybdenum(VI) complexes with water, 8-hydroxyquinoline and 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one. Geometrical parameters are optimized using B3PW91, B3LYP functionals in conjunction with def2-TZVP, LanL2DZ and 6-311 + G basis sets. Computed results show that the complex energetically prefers a pseudo-pentagonal bipyramidal shape in the ground state. The nature of intramolecular interactions between Mo(VI) and ligands is evaluated by analyzing the natural bond orbital and quantum theory of atoms in molecules. The Mo–OH2 interaction is rather weak with an average distance of 2.445 Å and a very low Mayer bond order of 0.235. The vibrational signatures and vertical electronic transitions of some excitations are examined and compared to available experimental data. The most favorable sites for electrophilic, nucleophilic attack or protonation were also identified using the noncovalent interaction method. [ABSTRACT FROM AUTHOR]

Leishmania (Mundinia) martiniquensis is responsible for visceral leishmaniasis in patients with no known underlying immunodeficiency, and visceral or disseminated cutaneous leishmaniasis in HIV-infected patients. The available anti-Leishmania drugs for treatment have limitations such as high toxicity and variable efficacy. To improve the therapeutic index of anti-Leishmania drugs, the search for a new drug or a new natural compound in combination therapy instead of using monotherapy to reduce drug side effect and have high efficacy is required. In this study, anti-Leishmania activity of 8-hydroxyquinoline (8HQN) and its synergistic effect with amphotericin B (AmB) against L. martiniquensis were evaluated in vitro for the first time. These results showed that 8HQN presented anti-Leishmania activity against L. martiniquensis with IC50 1.60 ± 0.28 and 1.56 ± 0.02 µg/mL for promastigotes and intracellular amastigotes, respectively. The selectivity index (SI) value of 8HQN was 79.84 for promastigotes and 82.40 for intracellular amastigotes, which highlight promising results for the use of 8HQN in the treatment of L. martiniquensis-infected host cells. Interestingly, four combinations of 8HQN and AmB provided synergistic effects for intracellular amastigotes and showed no toxic effects to host cells. These results provided information of using a combination therapy in treating this Leishmania species leads to further development of therapy and can be considered as an alternative treatment for leishmaniasis. [ABSTRACT FROM AUTHOR]

8‐Hydroxyquinoline (8HQ) and its derivatives display diverse bioactivities and therapeutic potentials. In this study, we unveiled that 8HQ can boost the peroxidase‐like activity of Co2+ in the presence of bicarbonate (HCO3−) in neutral pH at room temperature. With 2,2′‐azino‐bis‐(3‐ethylbenzothiazoline‐6‐sulphonate) (ABTS) as the substrate, the formed Co2+/8HQ/HCO3− complex shows robust catalytic activity with the turnover number (kcat) tens to hundreds of times higher than that of Co3O4 and other Co2+ complexes in terms of per cobalt ion. This system was used to design colorimetric sensors for ultrasensitive detection of 8HQ‐based drugs by activating the activity of Co2+. Take detecting clioquinol as an example, a detection limit of 2.4 nM clioquinol with a linear range from 0.01 to 0.2 μM was obtained. This work not only revealed a new kind of ligand that activated the activity of Co2+, but also provided a facile, low‐cost, ultrasensitive, easy‐to‐use, and universal strategy for sensing various 8HQ‐based drugs. Further development of this catalytic system might be beneficial to overcome drug resistance by combined medication. [ABSTRACT FROM AUTHOR]

The synthetic cannabinoids 5F-QUPIC and MDMB-CHMICA were sprayed on plant material intended for smoking and was seized as a criminal evidence. Their presence was confirmed by gas chromatography – mass spectrometry (GC-MS), and nuclear magnetic resonance (NMR). In the absence of analytical standards (indirect approach), the quantity of 5F-QUPIC in the herbal extract was determined by high-performance liquid chromatography with diode array detection (HPLC-DAD) based on total hydrolysis and measurement of the hydrolytic product (8-hydroxyquinoline) at 292 nm. The quantity of MDMB-CHMICA was determined using the ratio of 1H-NMR signals of both compounds in methanol-d4. 5F-QUPIC and MDMB-CHMICA in the herbal mixture were determined by the validated HPLC-DAD protocol by a direct approach with standards. [ABSTRACT FROM AUTHOR]

Objective(s): Breast cancer is a devastating disease related to women. The anticancer properties of 8-hydroxyquinoline (8HQ) and the increasing use of graphene oxide (GO), as a drug delivery system with anti-cancerous properties, led us to investigate the toxicity and apoptosis-induction capability of 8HQ-coated GO on breast cancer cells compared with normal breast cells.Materials and Methods: Breast cancer (MCF-7) and normal breast (MCF-10) cell lines were treated with several doses of 8-HQ-coated GO for 12, 24, and 48 hr. The toxicity of the nanocomposite was measured using MTT assay and the effect of the nanocomposite on cell apoptosis was determined by examining the expression of P53, P21, Bax, and BCL2 genes, as well as Annexin-V /PI apoptosis assay.Results: There were significantly increased cell deaths in nanocomposite-treated MCF-7 breast cancer cells, compared with treated normal breast cells. Significantly increased expression of P53, P21, and Bax genes and reduced expression of BCL2 gene were found in the treated breast cancer cell line compared with the normal cell line. Annexin-V/PI assay also illustrated significant induction of apoptosis in MCF-7 following nanocomposite treatment.Conclusion: Overall, 8HQ-coated GO has toxicity for breast cancer cell lines and one of the mechanisms through which this nanocomposite can induce cell death is the induction of apoptosis. With complementary in vitro and in vivo studies, this nanocomposite can be suggested as a nano-drug with anti-cancer properties.

Oscar Ekpenyong, Xiuqing Gao, Jing Ma, Candace Cooper, Linh Nguyen, Omonike A Olaleye, Dong Liang, Huan Xie Department of Pharmaceutical and Environmental Health Sciences, College of Pharmacy and Health Sciences, Texas Southern University, Houston, TX, USACorrespondence: Huan XieDepartment of Pharmaceutical and Environmental Health Sciences, College of Pharmacy and Health Sciences, Texas Southern University, 3100 Cleburne Street, Houston, TX 77004, USAEmail huan.xie@tsu.eduIntroduction: CLBQ14, a derivative of 8-hydroxyquinoline, exerts its chemotherapeutic effect by inhibiting methionine aminopeptidase (MetAP), the enzyme responsible for the post-translational modification of several proteins and polypeptides. MetAP is a novel target for infectious diseases. CLBQ14 is selective and highly potent against replicating and latent Mycobacterium tuberculosis making it an appealing lead for further development.Methods: The physicochemical properties (solubility, pH stability and lipophilicity), in vitro plasma stability and metabolism, pre-clinical pharmacokinetics, plasma protein binding and tissue distribution of CLBQ14 in adult male Sprague-Dawley rats were characterized.Results: At room temperature, CLBQ14 is practically insoluble in water (< 0.07 mg/mL) but freely soluble in dimethyl acetamide (> 80 mg/mL); it has a log P value of 3.03 ± 0.04. CLBQ14 exhibits an inverse Z-shaped pH decomposition profile; it is stable at acidic pH but is degraded at a faster rate at basic pH. It is highly bound to plasma proteins (> 91%), does not partition to red blood cells (B/P ratio: 0.83 ± 0.03), and is stable in mouse, rat, monkey and human plasma. CLBQ14 exhibited a bi-exponential pharmacokinetics after intravenous administration in rats, bioavailability of 39.4 and 90.0%, respectively from oral and subcutaneous route. We observed a good correlation between predicted and observed rat clearance, 1.90 ± 0.17 L/kg/h and 1.67 ± 0.08 L/kg/h, respectively. Human hepatic clearance predicted from microsomal stability data and from the single species scaling were 0.80 L/hr/kg and 0.69 L/h/kg, respectively. CLBQ14 is extensively distributed in rats; following a 5 mg/kg intravenous administration, lowest and highest concentrations of 15.6 ± 4.20 ng/g of heart and 405.9 ± 77.11 ng/g of kidneys, respectively, were observed. In vitro CYP reaction phenotyping demonstrates that CLBQ14 is metabolized primarily by CYP 1A2.Conclusion: CLBQ14 possess appealing qualities of a drug candidate. The studies reported herein are imperative to the development of CLBQ14 as a new chemical entity for infectious diseases.Keywords: CLBQ14, 8-hydroxyquinoline, methionine aminopeptidase, clioquinol, pharmacokinetics, tissue distribution, physicochemical, drug development

Two novel series of pyrazole and thiophene-linked quinoline analogues via amide bond were conveniently synthesized and characterized by IR, NMR, and HRMS analysis. The synthesized compounds were evaluated for their antimicrobial, anti-inflammatory, and anti-leukemic activity. The antimicrobial evaluation of the target compounds clearly showed that compound 11c has better activity compared to other compounds against tested pathogens. The anti-inflammatory assay of the selected compounds showed that 12c with IC50 value 118.73 µg/ml exhibited significant activity than standard drug Aspirin (IC50, 107.75 µg/ml). The compound 12a out of the twelve newly prepared quinoline heterocycles displayed superior antileukemic activity and was comparable with the standard drug against human monocytic leukemia cell lines (THP-1). Representing the two different quinolinyl-pyrazole/thiophene analogues, compounds 11d, 11e, and 12a displayed the remarkable cytotoxicity against THP-1 cell lines with IC50 values 112.46, 105.42, and 98.88 µg/ml respectively.

Leishmania (Mundinia) martiniquensis is responsible for visceral leishmaniasis in patients with no known underlying immunodeficiency, and visceral or disseminated cutaneous leishmaniasis in HIV-infected patients. The available anti-Leishmania drugs for treatment have limitations such as high toxicity and variable efficacy. To improve the therapeutic index of anti-Leishmania drugs, the search for a new drug or a new natural compound in combination therapy instead of using monotherapy to reduce drug side effect and have high efficacy is required. In this study, anti-Leishmania activity of 8-hydroxyquinoline (8HQN) and its synergistic effect with amphotericin B (AmB) against L. martiniquensis were evaluated in vitro for the first time. These results showed that 8HQN presented anti-Leishmania activity against L. martiniquensis with IC50 1.60 ± 0.28 and 1.56 ± 0.02 µg/mL for promastigotes and intracellular amastigotes, respectively. The selectivity index (SI) value of 8HQN was 79.84 for promastigotes and 82.40 for intracellular amastigotes, which highlight promising results for the use of 8HQN in the treatment of L. martiniquensis-infected host cells. Interestingly, four combinations of 8HQN and AmB provided synergistic effects for intracellular amastigotes and showed no toxic effects to host cells. These results provided information of using a combination therapy in treating this Leishmania species leads to further development of therapy and can be considered as an alternative treatment for leishmaniasis.

A simple and efficient protocol for the synthesis of the previously unknown 2-(2-(4-methoxyphenyl)furo[3,2-h]quinolin-3-yl)acetic acid was elaborated. The suggested method is based on the telescoped multicomponent reaction of 8-hydroxyquinoline, 4-methylglyoxal, and Meldrum’s acid. The studied process includes the initial interaction of the starting compounds in MeCN followed by intramolecular cyclization to the target product in refluxing acetic acid. The advantage of this approach is the application of readily available starting materials, atom economy, and a simple work-up procedure. The structure of the synthesized furylacetic acid derivative was proven by 1H, 13C, 2D-NMR, IR spectroscopy, and high-resolution mass spectrometry.

Two tetranuclear [Zn4Cl2(ClQ)6]·2DMF (1) and [Zn4Cl2(ClQ)6(H2O)2]·4DMF (2), as well as three dinuclear [Zn2(ClQ)3(HClQ)3]I3 (3), [Zn2(dClQ)2(H2O)6(SO4)] (4) and [Zn2(dBrQ)2(H2O)6(SO4)] (5), complexes (HClQ = 5-chloro-8-hydroxyquinoline, HdClQ = 5,7-dichloro-8-hydroxyquinoline and HdBrQ = 5,7-dibromo-8-hydroxyquinoline) were prepared as possible anticancer or antimicrobial agents and characterized by IR spectroscopy, elemental analysis and single crystal X-ray structure analysis. The stability of the complexes in solution was verified by NMR spectroscopy. Antiproliferative activity and selectivity of the prepared complexes were studied using in vitro MTT assay against the HeLa, A549, MCF-7, MDA-MB-231, HCT116 and Caco-2 cancer cell lines and on the Cos-7 non-cancerous cell line. The most sensitive to the tested complexes was Caco-2 cell line. Among the tested complexes, complex 3 showed the highest cytotoxicity against all cell lines. Unfortunately, all complexes showed only poor selectivity to normal cells, except for complex 5, which showed a certain level of selectivity. Antibacterial potential was observed for complex 5 only. Moreover, the DNA/BSA binding potential of complexes 1–3 was investigated by UV-vis and fluorescence spectroscopic methods.

A solid phase was developed by the fictionalization of silica fume with 8- hydroxyquinoline (SF-8HQ) through microwave-assisted solvent-free synthesis process for separation, removal and determination of Pb(II) in aqueous solutions. SF-8HQ was characterized by FTIR, XRD and SEM. The experimental conditions such as pH, shaking time, weight of sorbent and concentration of Pb(II) were optimized. It was found that SF-8HQ showed higher percentage of extraction (100.0 %) for Pb(II) and adsorption capacity value (171.55 mg g –1 ). The sorption kinetic data of Pb(II) on SF-8HQ was fitted to pseudo-second-order (r2 = 1). Moreover, the adsorption isotherm data for adsorption of Pb(II) was fitted to Langmuir and Freundlish isotherm models (r2 = 1). Breakthrough curves were analyzed at different bed heights as well as flow rates using fixed bed column. The practical applicability of SF-8HQ was examined to determine a trace amounts of Pb(II) in environmental water samples with high recovery values.

Both 8-hydroxyquinoline compounds and iridium (Ir) complexes have emerged as potential novel agents for tumor therapy. In this study, we synthesized and characterized two new Ir(III) complexes, [Ir(L1)(bppy)2] (Br-Ir) and [Ir(L2)(bppy)2] (Cl-Ir), with 5,7-dibromo-2-methyl-8-hydroxyquinoline (HL-1) or 5,7-dichloro-2-methyl-8-hydroxyquinoline as the primary ligand. Complexes Br-Ir and Cl-Ir successfully inhibited antitumor activity in Hep-G2 cells. In addition, complexes Br-Ir and Cl-Ir were localized in the mitochondrial membrane and caused mitochondrial damage, autophagy, and cellular immunity in Hep-G2 cells. We tested the proteins related to mitochondrial and mitophagy by western blot analysis, which showed that they triggered mitophagy-mediated apoptotic cell death. Remarkably, complex Br-Ir showed high in vivo antitumor activity, and the tumor growth inhibition rate was 63.0% (P < 0.05). In summary, our study on complex Br-Ir revealed promising results in in vitro and in vivo antitumor activity assays., (© The Author(s) 2024. Published by Oxford University Press.)

Multidrug resistance (MDR) in cancer is one of the major obstacles of chemotherapy. We have recently identified a series of 8-hydroxyquinoline Mannich base derivatives with MDR-selective toxicity, however with limited solubility. In this work, a novel 5-nitro-8-hydroxyquinoline-proline hybrid and its Rh(η5-C5Me5) and Ru(η6-p-cymene) complexes with excellent aqueous solubility were developed, characterized, and tested against sensitive and MDR cells. Complex formation of the ligand with essential metal ions was also investigated using UV-visible, circular dichroism, 1H NMR (Zn(II)), and electron paramagnetic resonance (Cu(II)) spectroscopic methods. Formation of mono and bis complexes was found in all cases with versatile coordination modes, while tris complexes were also formed with Fe(II) and Fe(III) ions, revealing the metal binding affinity of the ligand at pH 7.4: Cu(II) > Zn(II) > Fe(II) > Fe(III). The ligand and its Rh(III) complex displayed enhanced cytotoxicity against the resistant MES-SA/Dx5 and Colo320 human cancer cell lines compared to their chemosensitive counterparts. Both organometallic complexes possess high stability in solution, however the Ru(II) complex has lower chloride ion affinity and slower ligand exchange processes, along with the readiness to lose the arene ring that is likely connected to its inactivity.

Metallo‐β–lactamases (MBLs) are zinc‐containing carbapenemases that inactivate a broad range of β–lactam antibiotics. There is a lack of β–lactamase inhibitors for restoring existing β–lactam antibiotics arsenals against common bacterial infections. Fragment‐based screening of a non‐specific metal chelator library demonstrates 8‐hydroxyquinoline as a broad‐spectrum nanomolar inhibitor against VIM‐2 and NDM‐1. A hit‐based substructure search provided an early structure–activity relationship of 8‐hydroxyquinolines and identified 8‐hydroxyquinoline‐7‐carboxylic acid as a low‐cytotoxic β–lactamase inhibitor that can restore β–lactam activity against VIM‐2‐expressing E. coli. Molecular modeling further shed structural insight into its potential mode of binding within the dinuclear zinc active site. 8‐Hydroxyquinoline‐7‐carboxylic acid is highly stable in human plasma and human liver microsomal study, making it an ideal lead candidate for further development. [ABSTRACT FROM AUTHOR]

In our present research work, we have synthesized two ternary metal complexes of Mn(II), complex-I as [Mn(L)(Gly)(Cl)(H2O)] and complex-II as [Mn(L)(Q)(Cl)(H2O)]; where L is Isatinphenylhydrazone (IPH) as primary ligand, whereas glycine (Gly) and 8-hydroxyquinoline (HQ) as secondary ligand in complex-I and II respectively, in 1:1:1 (M: L: Gly or M: L: Q) molar ratios. Above synthesized complexes are employed for characterization using various analytical techniques including elemental analysis, melting point determination, magnetic moment measurements, molar conductance measurements, and spectral techniques (FTIR, UV, 1H NMR) etc. Further, their antimicrobial activities were evaluated against selected bacterial strains i.e., B. subtilis, S. aureus (Gram-positive) and P. aeruginosa, E. coli (Gram-negative) and fungal strains (T. reesei, A. niger, C. albicans) and found significantly active. [ABSTRACT FROM AUTHOR]

We disclose a nickel‐catalyzed reaction, which enabled us to difunctionalize unactivated γ,δ‐alkenes in ketones with alkenyl triflates and arylboronic esters. The reaction was made feasible by the use of 5‐chloro‐8‐hydroxyquinoline as a ligand along with NiBr2⋅DME as a catalyst and LiOtBu as base. The reaction proceeded with a wide range of cyclic, acyclic, endocyclic and exocyclic alkenyl ketones, and electron‐rich and electron‐deficient arylboronate esters. The reaction also worked with both cyclic and acyclic alkenyl triflates. Control experiments indicate that carbonyl coordination is required for the reaction to proceed. [ABSTRACT FROM AUTHOR]

Occlusion of the stem vasculature by microorganisms that proliferate in the vase water, or the plant vessels, leads to water stress symptoms that reduce postharvest quality of cut flowers. This study aimed to determine the effects of pulsing and wet-cold storage on the microbial profiles in cut Gladiolus grandiflorus L. cv. Fado. Pulsing treatments of 600-ppm 8-hydroxyquinoline sulfate plus 5% sucrose solution versus distilled water were administered before wet cold storage periods of 0–5 days in cut Gladiolus, previously grown from corms under open field. A two-by-six factorial experiment embedded in a completely randomized design with four replicates was accomplished. Proc GLM in two-way Anova was adopted, and the means were separated using Tukey’s test at a 5% level of significance. The pulsing treatment of 600 ppm 8-HQS plus 5% sucrose, the wet cold storage duration and their interactive effects significantly (P˂0.0209; ˂0.0001 and ˂0.0001 respectively) affected the means of the colony-forming units in the vase water of cut Gladiolus at senescence. The prolonged vase life of cut gladioli spikes was associated with decreased microbial proliferation as influenced by pulsing and wet storage duration of up to 4 days. Data generated from this study will improve existing technologies related to the quality and market value of this Gladiolus cultivar.

A new series of tin(II) complexes (1, 2, 4, and 5) were successfully synthesized by employing hydroxy functionalized pyridine ligands, specifically 2-hydroxypyridine (hpH), 8-hydroxyquinoline (hqH), and 10-hydroxybenzo[h]quinoline (hbqH) as stabilizing ligands. Complexes [Sn(μ-κ2ON-OC5H4N)(N{SiMe3}2)]2 (1) and [Sn4(μ-κ2ON-OC5H4N)6(κ1O-OC5H4N)2] (2) are the first structurally characterized examples of tin(II) oxypyridinato complexes exhibiting {Sn2(OCN)2} heterocyclic cores. As part of our study, 1H DOSY NMR experiments were undertaken using an external calibration curve (ECC) approach, with temperature-independent normalized diffusion coefficients, to determine the nature of oligomerisation of 2 in solution. An experimentally determined diffusion coefficient (298 K) of 6.87 × 10−10 m2 s−1 corresponds to a hydrodynamic radius of Ca. 4.95 Å. This is consistent with the observation of an averaged hydrodynamic radii and equilibria between dimeric [Sn{hp}2]2 and tetrameric [Sn{hp}2]4 species at 298 K. Testing this hypothesis, 1H DOSY NMR experiments were undertaken at regular intervals between 298 K–348 K and show a clear change in the calculated hydrodynamic radii form 4.95 Å (298 K) to 4.35 Å (348 K) consistent with a tetramer ⇄ dimer equilibria which lies towards the dimeric species at higher temperatures. Using these data, thermodynamic parameters for the equilibrium (ΔH° = 70.4 (±9.22) kJ mol−1, ΔS° = 259 (±29.5) J K−1 mol−1 and ΔG°298 = −6.97 (±12.7) kJ mol−1) were calculated. In the course of our studies, the Sn(II) oxo cluster, [Sn6(m3-O)6(OR)4:{Sn(II)(OR)2}2] (3) (R = C5H4N) was serendipitously isolated, and its molecular structure was determined by single-crystal X-ray diffraction analysis. However, attempts to characterise the complex by multinuclear NMR spectroscopy were thwarted by solubility issues, and attempts to synthesise 3 on a larger scale were unsuccessful. In contrast to the oligomeric structures observed for 1 and 2, single-crystal X-ray diffraction studies unambiguously establish the monomeric 4-coordinate solid-state structures of [Sn(κ2ON-OC9H6N)2)] (4) and [Sn(κ2ON-OC13H8N)2)] (5).

A new azo compound was prepared via the azo coupling reaction between 4-(ethoxycarbonyl)-3-methyl-1H-pyrazole-5-diazonium chloride and 8-hydroxyquinoline (oxine). The ester functional group of the obtained compound was hydrolyzed and thus a new chemical structure with a carboxylic functional group resulted. The structures of the new compounds were fully characterized by: UV–Vis, FT-IR, 1D and 2D NMR spectroscopy, and HRMS spectrometry.

The ligand N-(2-propionic acid)-salicyloylhydrazone(HL) and its new mixed ligand Zinc(II) complexes were synthesized and characterized by mass spectroscopy, IR spectroscopy and biological spectroscopy. The new mixed ligand Zinc complexes are Zn(C5H5N)(C10H9N2O4)C2H3O2, Zn(C10H8N2)(C10H9N2O4), Zn(C5H8N2)3 (C10H9N2O4), Zn(C10H9N2O4)(C9H6NO)(H4O2) and Zn(C10H9N2O4)(C14H11N2O2)(C2H3O2). These mixed complexes of zinc is prepared by reaction of HL (C10H9N2O4) and L1,L2,L3,L4,L5 in ethanol solution. [ABSTRACT FROM AUTHOR]

In this work, we report the results of a speciation study on the ternary complexes present in the systems formed by Ni(II) ion, 8-hydroxyquinoline (8-HQ) and the amino acids = α-alanine (HαAla), β-alanine (HβAla), phenylalanine (HPhe), proline (HPro), glycine (HGly), serine (HSer), threonine (HThr), aspartic acid (H2Asp), glutamic acid (H2Glu), methionine (HMet), histidine (H2His) and cysteine (H2Cys). The analysis involved the use of the potentiometric data with a least-squares program (LETAGROP) in aqueous 1 M NaCl solution at 25°C. The binary complexes formed in the system Ni(II) – 8-HQ in aqueous 1 M NaCl solution at 25°C were also determined and are presented here. [ABSTRACT FROM AUTHOR]

In this work, we report the synthesis of a new family of organic compounds based on 8-hydroxyquinoline using a simple and efficient method. The synthesized 8-hydroxyquinoline derivatives were characterized by analysis of 1H and 13C NMR, FT-IR spectral data and elemental analysis (EA). Their antibacterial activity is tested against Gram-positive strains [S. aureus (ATCC29213), V. parahaemolyticus (ATCC17802)] and Gram negative [E. coli (ATCC35218), P. aeruginosa (ATCC27853)] by the use of the agar diffusion technique. The obtained results showed that the synthesized 8-hydroxyquinoline derivatives have a potent antibacterial activity against the tested strains compared to Norfloxacin as a standard antibiotic. The results also reveal the effectiveness of these compounds at low concentrations, with a MIC of 1.00 μg/ml for compound 4a. Their antibacterial activity has also been optimized by bioinformatics studies (POM analyses). The experimental results are in relatively good agreement with the corresponding theoretical ones. [ABSTRACT FROM AUTHOR]

Fungal infections that affect humans and plants have increased significantly in recent decades. However, these pathogens are still neglected when compared to other infectious agents. Due to the high prevalence of these infections, the need for new molecules with antifungal potential is recognized, as pathogenic species are developing resistance to the main drugs available. This work reports the design and synthesis of 1,2,3-triazole derivatives of 8-hydroxyquinoline, as well as the determination of their activities against a panel of fungal species: Candida spp. , Trichosporon asahii, Magnusiomyces capitatus, Microsporum spp. , Trichophyton spp. and Fusarium spp. The triazoles 5-(4-phenyl-1 H -1,2,3-triazol-1-yl)quinolin-8-ol (12) and 5-(4-(cyclohex-1-en-1-yl)-1 H -1,2,3-triazol-1-yl)quinolin-8-ol (16) were more promising, presenting minimum inhibitory concentration (MIC) values between 1–16  µ g/ml for yeast and 2–4  µ g/ml for dermatophytes. However, no relevant anti- Fusarium spp. activity was observed. In the time-kill assays with Microsporum canis , 12 and 16 presented time-dependent fungicide profile at 96 h and 120 h in all evaluated concentrations, respectively. For Candida guilliermondii , 12 was fungicidal at all concentrations at 6 h and 16 exhibited a predominantly fungistatic profile. Both 12 and 16 presented low leukocyte toxicity at 4  µ g/ml and the cell viability was close to 100% after the treatment with 12 at all tested concentrations. The sorbitol assay combined with SEM suggest that damages on the fungal cell wall could be involved in the activity of these derivatives. Given the good results obtained with this series, scaffold 4-(cycloalkenyl or phenyl)-5-triazol-8-hydroxyquinoline appears to be a potential pharmacophore for exploration in the development of new antifungal agents. [ABSTRACT FROM AUTHOR]

The inhibition capacity of carbon steel (CS) in 0.5M H2SO4 by three 8-hydroxyquinoline grafted triazole derivatives (EHTC, AHTC, and MHTC) have been investigated using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PPD), and weight loss measurements (WLM) at 298 K. Generally, the results clearly show that the inhibition performance (η %) increases with an increase in the concentration of EHTC, MHTC, and AHTC, reaching a maximum value of 95.5% (EHTC), 95.1% (MHTC), and 94.1% (AHTC) at the optimal concentration (10−3 M) for PPD technical. The PPD shows that EHTC, AHTC, and MHTC behave as mixed-type inhibitors. In addition, the inhibitor obeys the single layer adsorption isotherm of Langmuir. Scanning electron microscopy (SEM) analysis of the CS has also been investigated and discussed. The theoretical calculations and MD simulations show a better correlation with the experimental results for the studied triazole derivatives. [ABSTRACT FROM AUTHOR]

• Ø A novel co-crystal of 8-hydroxyquinoline with acetone-(2,4-dinitrophenyl) hydrazone was isolated. • The considered co-crystal crystallizes in the triclinic P-1 space group. • The hydrogen bonding and π-π stacking are the main driving forces for the co-crystal building. • Energy framework analysis shows that interaction topology is driven by the dispersion energy. • The molecular docking study reveals that studied co-crystal has important antioxidant properties. Inspired by Betti reaction, a novel co-crystal of 8-hydroxyquinoline with acetone-(2,4-dinitrophenyl) hydrazone (I) was isolated in a one-pot 3 component assembly by reacting 8-hydroxyquinoline (8-HQ) with 2,4-dinitrohydrazine (DNPH) and formaldehyde. The crystal structure of (I) was characterized by single crystal X-ray diffraction analysis which shows that the hydrogen bonding and π-π stacking are the main driving forces for the co-crystal building. The topology of the intermolecular interaction energies in the crystal packing was analyzed and exposed using 3D energy framework analysis. The calculations of the studied molecule at the B3LYP levels in the 3-21g, 6-31g and 6-31++g** basis sets were made using the Gaussian package program. Theoretical calculations were executed to develop optimized geometry, frontier molecular orbital analysis and the NLO properties of the considered molecule, Furthermore, Molecular docking calculations were made. Afterwards, the interactions occurring in the docking calculation against the anti-oxidant protein (ID: 1HD2, 3NRZ, 4Z8D) were examined in detail with Schrödinger maestro. [Display omitted] [ABSTRACT FROM AUTHOR]