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PubMed2005

Synthesis and characterization of monomeric, oligomeric, and polymeric aluminum 8-hydroxyquinolines.

We report the synthesis and characterization of monomeric, oligomeric, and polymeric aluminum 8-hydroxyquinolines. The new structures of aluminum quinolate are contrived for expanding the application of AlQ(3) in the area of solution process by modifying AlQ(3) structure for improving solution processibility and crystallization resistance. Oligomeric aluminum 8-hydroxyquinoline (OALQ) was obtained using methylaluminoxane (MAO) and 8-hydroxyquinoline (8-HQ). Polymeric aluminum 8-hydroxyquinoline (PALQ) consists of 8-HQ and a polymeric Al-O backbone, simply prepared by stoichiometrically reacting 8-hydroxyquinoline, pentaerythritol propoxylate, and triethyl aluminum in the presence of chloroform. The absorption and emission spectra of OALQ and PALQ bear a clear resemblance to those of AlQ(3), and the molecular orbitals of OALQ and PALQ are virtually identical to those of AlQ(3). In the SEM images of AlQ(3) and OALQ, cylindrical rods of >100 microm in length and 5-10 microm in diameter for AlQ(3) and 20-100 microm in length and 1-5 microm in diameter for OALQ were observed, respectively. The size of the cylindrical rods of OALQ decreased compared with that of AlQ(3). As for the image of PALQ, an amorphous phase with bulge spots (ca. 5 microm) was observed. These microscope data correspond well to the X-ray powder pattern results. The chemical shifts (31.1, 57.0 ppm) and peak broadness of (27)Al NMR of AlQ(3) and its DFT calculation results present that mer- and fac-AlQ(3) appear in equilibrium through pentacoordinated intermediates. With the combination of DFT optimization and NMR calculation, models of OALQ and PALQ, hexa-, penta-, and tetracoordinated structures, were proposed, which exist in polymeric Al-O backbone and with inter- and intracoordination of Al-O bonds.

Journal Article↗
PubMed2005

6-hydroxyquinoline-N-oxides: a new class of "super" photoacids.

N-Oxidation of hydroxyquinolines leads to a dramatic increase in their excited-state acidity. Time-resolved and steady-state emission characterization of 6-hydroxyquinoline-N-oxide and 2-methyl-6-hydroxyquinoline-N-oxide reveals a rich but less complex proton-transfer behavior than that of its parent hydroxyquinoline. The electronic effect of the oxidized heterocyclic nitrogen atom makes the excited state both less basic and more acidic than the parent and adds hydroxyquinoline N-oxides to the class of high-acidity excited-state proton donors in photochemistry and photobiology. Adiabatic photoinduced proton transfer is accompanied by the efficient nonreversible deoxygenation and 1-2 oxygen migration.

Journal Article↗
PubMed1999

Syntheses and Metal Ion Complexation of Novel 8-Hydroxyquinoline-Containing Diaza-18-Crown-6 Ligands and Analogues.

Ten new 8-hydroxyquinoline-containing diaza-18-crown-6 ligands and analogues were synthesized via a one-pot or stepwise Mannich reaction, reductive amination, or by reacting diaza-18-crown-6 with 5,7-dichloro-2-iodomethyl-8-quinolinol in the presence of N,N-diisopropylethylamine. The Mannich reaction of N,N'-bis(methoxymethyl)diaza-18-crown-6 with 4-chloro-2-(1H-pyrazol-3-yl)phenol gave the NCH(2)N-linked bis(3-(5-chloro-2-hydroxy)pyrazol-1-ylmethyl)-substituted diazacrown ether (14) in a 98% yield. The reaction of bis(N,N'-methoxymethyldiaza)-18-crown-6 with 2.2 equiv of 10-hydroxybenzoquinoline gave only the monosubstituted diazacrown ether ligand (8). Interaction of some of the ligands with various metal ions was evaluated by a calorimetric titration technique at 25 degrees C in MeOH. Bis(8-hydroxyquinoline-2-ylmethyl)-substituted ligand 13 forms a very strong complex with Ba(2+) (log K = 11.6 in MeOH) and is highly selective for Ba(2+) over Na(+), K(+), Zn(2+), and Cu(2+) (selectivity factor > 10(6)). The (1)H NMR spectral studies of the Ba(2+) complexes with bis(8-hydroxyquinoline-2-ylmethyl)- and bis(5,7-dichloro-8-hydroxyquinoline-2-ylmethyl)-substituted diaza-18-crown-6 ligands (13 and 10) suggest that these complexes are cryptate-like structures with the two overlapping hydroxyquinoline rings forming a pseudo second macroring. UV-visible spectra of the metal ion complexes with selected ligands suggest that these ligands might be used as chromophoric or fluorophoric sensors.

Journal Article↗
PubMed1985

NTP Toxicology and Carcinogenesis Studies of 8-Hydroxyquinoline (CAS No. 148-24-3) in F344/N Rats and B6C3F1 Mice (Feed Studies).

Carcinogenesis studies of 8-hydroxyquinoline (99% pure), a metal chelator and antimicrobial agent, were conducted by administering the test chemical in feed to groups of 50 male and 50 female F344/N rats and B6C3F1 mice at concentrations of 0, 1,500, or 3,000 ppm for 103 weeks. These concentrations were selected because the chemical at higher concentrations resulted in reduced feed consumption, decreases in mean body weights, and deaths in the 15-day and 13-week studies. The average daily doses were estimated to be 73 and 143 mg/kg for male rats, 89 and 166 mg/kg for female rats, 217 and 396 mg/kg for male mice, and 349 and 619 mg/kg for female mice. Survival of dosed male and female rats and mice in the 2-year studies was comparable to that of the corresponding controls. The high dose rats and mice of each sex exhibited slight decreases in mean body weights and decreased feed consumption. Compound-related gross or microscopic pathologic effects were not observed in either species in the 15-day or 13-week studies. In the 2-year studies, C-cell adenomas/carcinomas of the thyroid gland showed a positive trend (P=0.03) for male rats (control, 1/50; low dose, 1/49; high dose, 6/47). The incidence of C-cell neoplasms in the high dose was not significantly increased compared with the controls, and the occurrence of C-cell hyperplasia was not elevated (4/50; 3/49; 1/47). The incidence of alveolar/bronchiolar adenomas or carcinomas (combined) in male rats with a positive trend, and the incidence in the high dose group was greater than that in the controls (0/50; 3/50; 4/50). This marginal effect was not supported by an increase in epithelial hyperplasia (5/50; 5/50; 3/50). These marginal increases in male rats were not regarded as being related to the administration of 8-hydroxyquinoline. In in vitro tests, 8-hydroxyquinoline did not induce either unscheduled DNA synthesis in rat hepatocytes or transformation of BALB/c-3T3 cells. An audit of the experimental data for these carcinogenesis studies on 8-hydroxyquinoline was conducted. No data discrepancies were found that significantly influenced the final interpretations. Under the conditions of these studies, there was no evidence of carcinogenicity for male and female F344/N rats or for male and female B6C3F1 mice given 8-hydroxyquinoline in feed at concentrations of 1,500 or 3,000 ppm for 103 weeks. Synonyms: 8-quinolinol; oxine; hydroxybenzopyridine

Journal Article↗
PubMed1976

Synthesis and in vitro evaluation of 8-hydroxyquinoline analogs as inhibitors of dental plaque.

A group of 5-substituted 8-hydroxyquinolines with predicted log P values in the 1-4 range has been prepared from either 8-hydroxyquinoline or its appropriate derivative. 5-Formyl-, 5-iodo-, 5-fluoro-, 5-acetyl-, and 5-methoxymethyl-8-hydroxyquinoline in addition to methyl-5(8-hydroxyquinolyl)acetate and ethyl 5-(8-hydroxyquinolyl)acetate displayed greater in vitro antiplaque activity than 8-hydroxyquinoline.

Dental Plaque↗
PubMed2002

Study of in vitro glucuronidation of hydroxyquinolines with bovine liver microsomes.

Glucuronidation of drugs by UDP-glucuronosyltransferase (UGT) is a major phase II conjugation reaction. Defects in UGT are associated with Crigler-Najjar syndrome and Gilbert's syndrome with severe hyperbilirubinaemias and jaundice. We analysed the reactivities of some hydroxyquinoline derivatives, which are naturally produced from quinoline by cytochrome P450. The analyses were carried out using a microassay system for UGT activity in bovine liver microsomes in the range 0.5-100 pmol/assay with the highly sensitive radio-image analyser Fuji BAS2500 (Fujifilm, Tokyo, Japan). 3-Hydroxylquinoline is a good substrate for glucuronidation, and the relative Kcat values were 3.1-fold higher than the values for p-nitrophenol. 5,6-Dihydroquinoline-5,6-trans-diol gave a similar Km value to that of 3-hydroxyquinoline, but the Vmax value was approximately 1/15 of that of p-nitrophenol and showed weak reactivity. Quinoline N-oxide gave a low Vmax value and showed marginal activity. The Kcat values of 6-hydroxyquinoline and 5-hydroxyquinoline were 2.1- and 1.2-fold higher than that of p-nitrophenol, respectively. Fluoroquinoline (FQ) derivatives, such as 3FQ, 7.8diFQ and 6,7,8triFQ, did not show any substrate activities. These results suggest that there are therapeutic problems in administration of some quinoline drugs to patients with jaundice.

Animals↗
PubMed1992

2-Heptyl-4-hydroxyquinoline N-oxide, an antistaphylococcal agent produced by Pseudomonas aeruginosa.

Clinical isolates of Pseudomonas aeruginosa produce low molecular weight, hydrophobic substances which inhibit the growth of Staphylococcus aureus and other Gram-positive organisms. The active substances have been purified from a culture of P. aeruginosa and characterized as a mixture of 2-heptyl-4-hydroxyquinoline N-oxide and its homologues. The alkyl-hydroxyquinolines (derived through reduction of the N-oxide) were also produced by P. aeruginosa cultures but, in general, were less active against S. aureus. 2-Heptyl-4-hydroxyquinoline was identified in a sample of human bronchial secretions from a patient with cystic fibrosis who was heavily colonized with P. aeruginosa. Production of antibacterial alkyl-hydroxyquinoline N-oxides in human lung may explain the observation that the presence of P. aeruginosa in the sputum of patients with cystic fibrosis is correlated with the absence of S. aureus.

Chromatography, High Pressure Liquid↗
PubMed2003

Hydroxyquinolines as iron chelators.

The interest in synthetic siderophore mimics includes therapeutic applications (iron chelation therapy), the design of more effective agents to deliver Fe to plants and the development of new chemical tools for studies of iron metabolism and for a better understanding of iron assimilation processes in living systems. The 8-hydroxyquinoline bidentate chelate moiety offers an alternative to the usual hydroxamic acid, catechol and/or alpha-hydroxycarboxylic acid metal-binding groups encountered in natural siderophores. The promising results obtained by the tris hydroxyquinoline-based ligand O-TRENSOX are summarized. O-TRENSOX exhibits a high and selective affinity for Fe(III) complexation. Its efficiency in delivering Fe to plants as well as its efficiency for iron mobilization, cellular protection and antiproliferative effects have been evidenced. Other chelators of the O-TRENSOX family (mixed catechol / 8-hydroxyquinoline ligands, lipophilic ligands) are also described. Some results question whether the use of partition coefficients is pertinent to foresee the activity of iron chelators. The development of probes (fluorescent, radioactive, spin labelled) based on the O-TRENSOX backbone is in progress. 8-hydroxyquinoline iron chelators seem to have a promising future.

Animals↗
PubMed2003

Quinolinate dehydrogenase and 6-hydroxyquinolinate decarboxylase involved in the conversion of quinolinic acid to 6-hydroxypicolinic acid by Alcaligenes sp. strain UK21.

In the conversion of quinolinic acid to 6-hydroxypicolinic acid by whole cells of Alcaligenes sp. strain UK21, the enzyme reactions involved in the hydroxylation and decarboxylation of quinolinic acid were examined. Quinolinate dehydrogenase, which catalyzes the first step, the hydroxylation of quinolinic acid, was solubilized from a membrane fraction, partially purified, and characterized. The enzyme catalyzed the incorporation of oxygen atoms of H(2)O into the hydroxyl group. The dehydrogenase hydroxylated quinolinic acid and pyrazine-2,3-dicarboxylic acid to form 6-hydroxyquinolinic acid and 5-hydroxypyrazine-2,3-dicarboxylic acid, respectively. Phenazine methosulfate was the preferred electron acceptor for quinolinate dehydrogenase. 6-Hydroxyquinolinate decarboxylase, catalyzing the nonoxidative decarboxylation of 6-hydroxyquinolinic acid, was purified to homogeneity and characterized. The purified enzyme had a molecular mass of approximately 221 kDa and consisted of six identical subunits. The decarboxylase specifically catalyzed the decarboxylation of 6-hydroxyquinolinic acid to 6-hydroxypicolinic acid, without any co-factors. The N-terminal amino acid sequence was homologous with those of bacterial 4,5-dihydroxyphthalate decarboxylases.

Alcaligenes↗
PubMed2002

Suppression of pyrite oxidation by iron 8-hydroxyquinoline.

One of the important approaches to prevent pyrite (FeS(2)) oxidation and subsequent formation of acid mine drainage (AMD) is to create a surface coating on pyrite. In this study, a coating of iron 8-hydroxyquinoline was formed by leaching pyrite with a 0.10 M H(2)O(2)/0.0034 M 8-hydroxyquinoline solution; stability of the coated pyrite was tested under various pH and temperature conditions. The results showed that iron 8-hydroxyquinoline coating could significantly suppress further pyrite oxidation by both chemical (H(2)O(2)) and biological ( e.g., Thiobacillus ferrooxidans) processes. At pH from 3.0 to 5.0 and temperature from 10-40 degrees C, the amount of SO(4)(2-) leached out by 0.10 M H(2)O(2) from the coated pyrite samples was 54.8-70.1% less than that from the uncoated controls. The oxidation of pyrite followed a pseudo-zero-order kinetics under the constant concentration of H(2)O(2). In the presence of microorganisms, sulfate leached out of the uncoated pyrite in 1 year accounted for 5.32% of the total pyrite in the system, with a concurrent pH drop to 2.35 under the ambient room temperatures. In contrast, the amount leached out from the coated samples was only 0.15% of the total pyrite and the final pH was 5.48. Thus, the coating decreased the leachability of pyrite by 97% in the inoculated systems. In comparison to the more widely studied iron phosphate coating, the advantage of iron 8-hydroxyquinoline coating was that it inhibited both chemical and biological pyrite oxidation, whereas iron phosphate coating could only inhibit chemical pyrite oxidation.

Equipment Design↗
PubMed2001

Bis-8-hydroxyquinoline-armed diazatrithia-15-crown-5 and diazatrithia-16-crown-5 ligands: possible fluorophoric metal ion sensors.

The synthesis and preliminary photophysical properties of a series of diazatrithia-15-crown-5 and diazatrithia-16-crown-5 ligands containing two 8-hydroxyquinoline sidearms are reported. The ligands were prepared by a two-step process. First, diazatrithiacrown ethers 11 and 12 were prepared by treating bis(alpha-chloroamide) 5 with various dimercaptans followed by reduction using a boron-THF complex. Hydroxymethyl-substituted macrocycle 12 was rearranged to hydroxy-substituted diazatrithia-16-crown-5 in refluxing aqueous HCl. Macrocyclic diamines 11-13 were converted to either 5-chloro-8-hydroxyquinolin-7-ylmethyl-substituted diazatrithiacrown ethers 14-16 by a Mannich aminomethylation reaction or to 8-hydroxyquinolin-2-ylmethyl-substituted diazatrithiacrown ethers 17-19 by reductive amination using 8-hydroxyquinoline-2-carboxaldehyde. Preliminary photophysical studies show that ligands 16 and 19 exhibit increased fluorescence in the presence of Zn(2+), indicating that these ligands could be chemical sensors for Zn(2+).

Journal Article↗
PubMed1977

Quantitative structure-activity relationships for 5-substituted 8-hydroxyquinolines as inhibitors of dental plaque.

Fourteen 8-hydroxyquinolines were tested for antiplaque activity by measuring their minimum inhibitory concentrations [MIC (M)] against Streptococcus mutans No. 6715. Linear regression analysis was conducted with the MIC (M) values and hydrophobic (log P), electronic (beta, pKaOH, pKaN), and steric [molar refractivity (MR), molecular weight (mol wt)] parameters. The best correlation (r2 = 0.90) was obtained with MR, log P, and beta. The smaller the steric contribution of the 5-substituent, the more active the compound. The parent 8-hydroxyquinoline was the most active. The negative contribution toward activity by 5-substituents larger than hydrogen can be overcome by the positive contributions of groups that are lipophilic and electron withdrawing; for example, the 5-chloro derivative is as active as the parent 8-hydroxyquinolines.

Dental Plaque↗
PubMed1987

Synthesis and antitumor activity of tropolone derivatives. 6. Structure-activity relationships of antitumor-active tropolone and 8-hydroxyquinoline derivatives.

The bis derivative 6 of 8-hydroxyquinoline, which, like tropolones, readily forms a chelate, was synthesized and found to have high potency (dose = 12.5 mg/kg, T/C % = 164) against leukemia P388 in mice approximately equivalent to that of the bistropolone 1b. 8-Hydroxyquinoline analogues with broad structural variation were synthesized and their structure-activity relationships followed the same pattern as in the tropolone series. In addition, the bistropolones 1a-e were tested for their ability to bind to tubulin and found to have no such property. The results of this study suggested that bistropolone and bis(8-hydroxyquinoline) derivatives must form a chelate with the metal necessary for the enzyme, such as ribonucleotide reductase, which catalyzes the DNA biosynthetic pathways.

Animals↗
PubMed1991

Separation of hydroxyquinolines by high-performance liquid chromatography.

1. Hydroxyquinolines are important chemicals for pharmaceutical and cosmetic use. This report describes an improved method for separating these chemicals, by utilizing a high-performance liquid chromatography technique. 2. 8-Hydroxyquinoline is an excellent chelating agent. Previous separation procedures failed because of this property. An important requirement for the success of the method described is to provide a metal-free environment for the separation of hydroxyquinolines by replacing metal tubing with Polyplex and polyether-ether ketone (PEEK) tubing and utilizing a metal-free Hamilton PRP-1 column.

Chromatography, High Pressure Liquid↗
PubMed1979

Combined cycloheximide and 8-hydroxyquinoline pretreatment for study of plant chromosomes.

The actions of cycloheximide and 8-hydroxyquinoline on dividing cells of root meristems of Zea mays L. have been studied during the development of a new cytological technique for sugar cane (Saccharum) root tips. The determination of mitotic phase indices revealed that combined treatment with cycloheximide (70 ppm) plus 8-hydroxyquinoline (250 ppm) was superior to treatments with either chemical separately. After the combined treatment, the preparations contained nearly ten times more cells in prophase and metaphase that were suitable for chromosome counting than those given a single pretreatment with 8-hydroxyquinoline. This new pretreatment has been developed especially for chromosome studies in tropical grasses with a large number of small chromosomes. However, both chemicals are active in a wide range of plant species.

Chromosomes↗
PubMed1986

A clinical trial of hydrocortisone/potassium hydroxyquinoline sulphate ('Quinocort') in the treatment of infected eczema and impetigo in general practice.

A double-blind, multi-centre study was carried out in general practice in 76 patients with infected eczema and 43 with impetigo to assess the effectiveness and acceptability of treatment with 1% hydrocortisone plus 0.5% potassium hydroxyquinoline sulphate cream compared with that of 1% hydrocortisone plus 2% miconazole nitrate cream. Patients were allocated at random to receive treatment with one or other preparation, applied twice daily, over a period of 2 weeks. Assessments were made of total symptom severity scores on entry and at the end of each week, as also were bacteriological investigations. The results showed that both combinations produced marked clinical and bacteriological improvement or cure in approximately 90% of patients with infected eczema and the success rate was similar with each preparation. In the case of patients with impetigo, hydrocortisone/potassium hydroxyquinoline sulphate proved significantly more effective than the other combination, the success rates being 92% and 74%, respectively. Patient assessment of the two topical preparations in terms of greasiness, odour and staining showed that, whilst both were considered acceptable by most, there was a trend in favour of the hydrocortisone/potassium hydroxyquinoline sulphate cream. No systemic or local side-effects were reported.

Adolescent↗
PubMed2006

8-Hydroxyquinoline derivatives induce the proliferation of rat mesenchymal stem cells (rMSCs).

A series of 8-hydroxyquinoline derivatives with different substituted groups at 2- or 5-position have been synthesized and characterized. Their effects on the proliferation of the rat marrow-derived mesenchymal stem cells (rMSCs) have been evaluated by MTT assay and flow cytometry. We also analyzed the ability of these compounds to regulate the proliferation of rMSCs and the relationship with the structures of 8-hydroxyquinoline. Compounds 8-11, in which, the vinyl-substituents are on the 2-position of 8-hydroxyquinoline, appear to be able to induce the proliferation of rMSCs. These results show that compounds 8-11 provide a kind of new substances for regulating the proliferation of rMSCs.

Animals↗
PubMed2002

Electroluminescent zinc(II) bis(8-hydroxyquinoline): structural effects on electronic states and device performance.

We present direct evidence for stable oligomers in vacuum-deposited thin films of zinc(II) bis(8-hydroxyquinoline) (Znq(2)). The tetramer [(Znq(2))(4)] is the energetically favored configuration in both the single crystal and the vacuum-deposited thin film. Oligomerization leads to distinct, symmetry-driven differences between the electronic states in Znq(2) and those in the archetypal organic electroluminescent molecule tris(8-hydroxyquinoline) aluminum (Alq(3)). In the case of the Znq(2) tetramer, symmetry leads to an extended network of overlapping pyridyl and phenolato moieties in the solid film. Analysis of the electronic structure of (Znq(2))(4) calculated by ab initio Hartree-Fock (HF) methods reveals a localization and energy shift of high-lying occupied and low-lying unoccupied states on symmetry related ligands located on opposite sides of the supramolecular structure resulting in a dipole moment for (Znq(2))(4) tetramer close to zero. The optimal pi-overlap pathways, altered charge distributions, and extended electronic states of tetrameric Znq(2) may be expected to enable low operating voltage organic light-emitting devices (OLEDs) based on Znq(2). We present preliminary evidence that the operating voltage of (Znq(2))(4)-based OLEDs is indeed lower than that of identical devices made with Alq(3). Strategic substitution of 8-hydroxyquinoline ligands and control of the structural symmetry of the corresponding metal chelates may offer a route to high efficiency and low operating voltage small molecule OLEDs.

Journal Article↗