Amplified Peroxidase-like Activity of Co2+ Using 8-Hydroxyquinoline and Its Application for Ultrasensitive Colorimetric Detection of Clioquinol.

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 Co3 O4 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.

Electrocatalytic evaluation of graphene oxide warped tetragonal t-lanthanum vanadate (GO@LaVO4) nanocomposites for the voltammetric detection of antifungal and antiprotozoal drug (clioquinol).

Metastable and rarely reported GO warped tetragonal phase t-lanthanum vanadate nanocomposites (GO@LaVO4-NCs) are reported for the sensitive electrochemical determination of antifungal drug Clioquinol (CQ). The hydrothermal method was adopted for synthesis of GO@LaVO4-NCs. The electrochemical performance of CQ was examined using cyclic voltammetry (CV) and differential plus voltammetry (DPV) at GO@LaVO4-NCs modified glassy carbon electrode (GCE). The electrocatalytic oxidation of CQ at the GO@LaVO4-NCs/GCE shows the highest anodic peak current at a potential of +0.51 V vs. Ag/AgCl. The proposed sensor provides excellent sensitivity of 4.1894 µA µM-1 cm-2, a very low detection limit (LOD) of 2.44 nM, and a wide range of 25 nM to 438.52 µM towards CQ detection. Finally, the detection of CQ in biological media was successfully done using the GO@LaVO4-NCs/GCE and possesses recoveries of 94.67-98.0%.

Coupling of liquid-liquid extraction and mathematical filtration techniques for the separation and quantification of five components in semisolid dosage form with severely overlapped spectra.

Quadriderm cream was a combination of four components; Clioquinol (CLIO), Betamethasone (BETA), Tolnaftate (TOL), Gentamicin (GEN) in addition to the preservative Chlorocresol (CC). Four components CLIO, TOL, BETA, and CC were extracted in methanol and determined by mathematic filtration spectrophotometric techniques. The partially overlapped spectrum of CLIO was determined by constant value, constant multiplication, and concentration value methods then eliminated via spectrum subtraction (SS) to get the resolved ternary mixture of TOL, BETA, and CC with severely overlapping spectra. TOL was determined by derivative ratio at zero crossing point of BETA using CC as a divisor. While, BETA could be determined using TOL as a divisor at zero crossing of CC. BETA and CC were obtained using novel (DD1FS) followed by SS. By applying these novel procedures, the DD1 spectrum of each component alone was recovered where Pmax-min was directly proportional to its concentration. Liquid-liquid extraction technique was used for the semisolid dosage form where GEN was extracted with a mixture of chloroform: water (50:50, v/v); and the induced fluorescence obtained by derivatization with o-phthalaldehyde was measured at 419 nm after excitation at 359 nm. Accuracy and precision testing of the developed methods showed good results. Specificity of the methods was ensured and was successfully applied for the analysis of pharmaceutical formulation of the five components in combination. ICH guidelines were used for validation of the proposed methods. Statistical data were calculated, and the results were satisfactory revealing no significant difference regarding accuracy and precision.

Using zinc ion-enhanced fluorescence of sulfur quantum dots to improve the detection of the zinc(II)-binding antifungal drug clioquinol.

A turn on-off fluorometric assay for clioquinol (CQ) is described here. It is based on modulation of the fluorescence of sulfur quantum dots (SQDs; best measured at excitation/emission wavelengths of 360/426 nm) by using the Zn2+-CQ affinity pair. Although the fluorescence enhancement effect of Zn2+ on SQDs was not obvious, a good quenching modulation effect was observed in the presence of CQ. This resulted in a linear analytical range that is increased by two orders of magnitude (from 0.024 µM to 0.24 µM, and 0.62 µM to 30 µM), with a detection limit (3 s) of 0.015 µM. The selectivity of the method is also improved. Graphical abstractSchematic illustration of the turn on-off fluorometric assay for for clioquinol (CQ) based on Zn2+-modulated sulfur quantum dots (SQDs).

New record of Scedosporium dehoogii from Chile: phylogeny and susceptibility profiles to classic and novel putative antifungal agents / Scedosporium dehoogii, un nuevo reporte de Chile: filogenia y perfiles de sensibilidad a antifúngicos clásicos y a nuevas moléculas con potencial antifúngico

Background. Scedosporium species are considered emerging agents causing illness in immunocompromised patients. In Chile, only Scedosporium apiospermum, Scedosporium boydii and Lomentospora prolificans haven been reported previously. Aims. The study aimed to characterize genetically Scedosporium dehoogii strains from Chilean soil samples, and assessed the antifungal susceptibility profile to classic and novel putative antifungal molecules. Methods. In 2014, several samples were obtained during a survey of soil fungi in urban areas from Chile. Morphological and phylogenetic analyses of the internal transcribed spacer region (ITS), tubulin (TUB), and calmodulin (CAL) sequences were performed. In addition, the susceptibility profiles to classic antifungal and new putative antifungal molecules were determined. Results. Four strains of Scedosporium dehoogii were isolated from soil samples. The methodology confirmed the species (reported here as a new record for Chile). Antifungal susceptibility testing demonstrates the low activity of terpenes (α-pinene and geraniol) against this species. Voriconazole (VRC), posaconazole (PSC), and the hydroxyquinolines (clioquinol, and 5,7-dibromo-8-hydroxyquinoline) showed the best antifungal activity. Conclusions. Our results demonstrate that Scedosporium dehoogii is present in soil samples from Chile. This study shows also that hydroxyquinolines have potential as putative antifungal molecules (AU)

Antecedentes. Las especies de Scedosporium se consideran agentes emergentes responsables de enfermedad en pacientes inmunodeficientes. En Chile, únicamente se había publicado con anterioridad la existencia de las especies Scedosporium apiospermum, Scedosporium boydii y Lomentospora prolificans. Objetivos. Este estudio tuvo como objetivo clasificar genéticamente aislamientos de Scedosporium dehoogii obtenidos de muestras del suelo de Chile. Asimismo, se evaluó el perfil de sensibilidad de las cepas a los antifúngicos clásicos y a nuevas moléculas con potencial antifúngico. Métodos. En el año 2014, durante un estudio de evaluación de la biodiversidad fúngica en Chile, se tomaron diversas muestras del suelo de zonas urbanas del país. Se llevaron a cabo análisis morfológicos y filogenéticos de las secuencias pertenecientes a la región del espaciador transcrito interno (ITS), de la tubulina (TUB) y de la calmodulina (CAL). Además, se determinaron los perfiles de sensibilidad a los antifúngicos clásicos y a nuevas moléculas con potencial antifúngico. Resultados. Se aislaron cuatro cepas de Scedosporium dehoogii de las muestras del suelo. Las pruebas morfológicas y moleculares confirmaron la especie (el presente estudio representa un nuevo reporte para Chile). Las pruebas de sensibilidad antifúngica mostraron baja actividad de los terpenos (α-pineno y geraniol). El voriconazol (VRC), el posaconazol (PSC) y las hidroxiquinolinas (clioquinol y 5,7-dibromo-8-hidroxiquinolina) presentaron la mejor actividad antifúngica. Conclusiones. Nuestros estudios demuestran que Scedosporium dehoogii está presente en los suelos de Chile. Asimismo, este estudio sugiere que las hidroxiquinolinas desempeñan una potencial actividad antifúngica (AU)

Cu(2+)-mediated fluorescence switching of gold nanoclusters for the selective detection of clioquinol.

It is of great significance to sense clioquinol (CQ) in a simple and fast way because of its potential application in the treatment of neurodegenerative diseases. In this contribution, we proposed a Cu(2+)-mediated fluorescence switchable strategy to detect CQ by taking bovine serum albumin (BSA) protected gold nanoclusters (AuNCs) as probes. It was found that the strong red fluorescence of BSA-protected AuNCs at 610 nm could be effectively quenched by Cu(2+) (off state) and reversibly recovered by CQ (on state) owing to the specific coordination of CQ and Cu(2+). Under the optimal conditions, there was a good linear relationship between the off-on efficiency (Eoff-on) and the amount of CQ in the range of 1-12 µM (R(2) = 0.9902), with a detection limit of 0.63 µM (3σ). The "turn off-on" mode and the fast and unique complexation of CQ and Cu(2+) endow AuNCs with high specificity for CQ sensing. The proposed strategy is label-free, fast and selective, which is applicable to the analysis of CQ in cream with satisfactory results.

Novel spectrophotometric determination of flumethasone pivalate and clioquinol in their binary mixture and pharmaceutical formulation.

This work is concerned with development and validation of three simple, specific, accurate and precise spectrophotometric methods for determination of flumethasone pivalate (FP) and clioquinol (CL) in their binary mixture and ear drops. Method A is a ratio subtraction spectrophotometric one (RSM). Method B is a ratio difference spectrophotometric one (RDSM), while method C is a mean center spectrophotometric one (MCR). The calibration curves are linear over the concentration range of 3-45 µg/mL for FP, and 2-25 µg/mL for CL. The specificity of the developed methods was assessed by analyzing different laboratory prepared mixtures of the FP and CL. The three methods were validated as per ICH guidelines; accuracy, precision and repeatability are found to be within the acceptable limits.

HPLC method for identification and quantification of three active substances in a dermatological preparation--Viosept ointment.

The study was aimed at developing a HPLC method to identify and quantify domiphen bromide, tripelennamine hydrochloride and clioquinol in Viosept ointment. The tested substances were successfully separated using Inertsil ODS-3 (250 x 4.6 mm, 5 µm) as a stationary phase and a gradient elution. Detection at 310 nm wavelength was applied for tripelennamine hydrochloride and clioquinol, and at 215 nm wavelength for domiphen bromide. Methods of extraction of the tested substances were developed: domiphen bromide and clioquinol were extracted with acetone from heated solutions, and tripelennamine hydrochloride was extracted in a hexane-water system. Validation procedure confirmed the method to be sufficiently selective, precise and accurate. Correlation coefficients of calibration curves pointed out that they were linear within the examined concentration range.

Anodic behavior of clioquinol at a glassy carbon electrode.

Clioquinol is an antifungal, antiprotozoal and an Alzheimer's disease drug with cytotoxic activity toward human cancer cells. The electrochemical behavior of clioquinol and its oxidation product was studied using cyclic, differential pulse and square-wave voltammetry over a wide pH range on a glassy carbon electrode. The results revealed that the oxidation of clioquinol is an irreversible pH-dependent process that proceeds with the transfer of one electron and one proton in an adsorption-controlled mechanism and results in the formation of a main oxidation product, which adsorbs very strongly on the glassy carbon surface. The charge transfer coefficient was calculated as 0.64. The adsorbed oxidation product presented reversible redox behavior, with two electron and two proton transfer. The electrochemical oxidation of clioquinol as a phenolic compound involves the formation of a phenoxy radical which reacts in at least two ways: in one pathway the radical initiates polymerization, the products remaining at the electrode surface, and in the other the radical is oxidized to a quinone-like structure. A mechanism for the oxidation of clioquinol is proposed.

LC of pharmaceutically important halogenated 8-hydroxyquinolines after precolumn derivatization with Pd (II).

An accurate, sensitive, and selective reversed phase high performance liquid chromatographic (HPLC) method was developed for the analysis of two halogenated 8-hydroxyquinoline derivatives; clioquinol (CQN) and iodoquinol (IQN). The proposed method depends on the complexation ability of the studied compounds with Pd(II) ions. Reversed phase chromatography was conducted using a 300 x 3.9 mm i.d. stainless steel column packed with 10 microm Bondclone phenyl at ambient temperature. A solution containing 0.005% w/v of Pd(II)-chloride in a mixture of acetonitrile-methanol-water (3:3:4 v/v/v) of pH 3.7 as a mobile phase pumped at a flow rate of 0.75 ml min(-1). UV-detection was performed at 282 and 285 nm for CQN and IQN, respectively. The method showed excellent linearity in the range 0.05-1.8 and 0.1-3.0 microg ml(-1) with limit of detection (S/N=2) 4.8 ng ml(-1) (1.57 x 10(-8) M) and 6.4 ng ml(-1) (1.61 x 10(-8) M) for CQN and IQN, respectively. The suggested method was successfully applied for the analysis of the studied drugs in bulk with average% recoveries of 99.68+/-0.44 for CQN and 99.65+/-0.53 for IQN. The proposed method was successfully applied for the analysis of the studied drugs in single or combined dosage forms with average% recoveries of 99.41+/-0.51-100.02+/-0.63. The proposed method could be used successfully for the determination of the studied compounds in the presence of their degradation product as they could be eluted with different retention times. The presence of metronidazole (MNZ) or tolnaftate (TFT) with the studied drugs does not affect their accurate determination. The results obtained were favorably compared with those obtained by the reference method. The results were satisfactorily, accurate, and precise.

Reverse-phase liquid chromatographic determination of clioquinol in cream and ointment preparations: collaborative study.

Seven laboratories participated in a collaborative study to analyze, in duplicate, 2 synthetic formulations and 2 commercial preparations, labeled to contain 3% clioquinol. Clioquinol is determined as its nickel (II) complex by reverse-phase liquid chromatography on a phenyl-bonded column with a mobile phase of acetonitrile-methanol-water, containing ammonium acetate and nickel chloride. Detection is at 273 nm and diphenylamine is added as an internal standard. Mean recoveries were 99.1 and 101.1%, respectively, for the ointment and cream synthetic preparations and 96.7 and 99.7%, respectively, for the commercial ointment and cream. All results are consistent with the variability of other methods at this concentration range. The method has been approved interim official first action.

Determination of chinoform in biological fluids and nervous tissues of the dog by gas chromatography-mass spectrometry.

A sensitive gas chromatographic-mass spectrometric method for the determination of 5-chloro-7-iodo-8-hydroxyquinoline (chinoform, clioquinol) in biological fluids and nervous tissues is described. Chinoform was converted into the pentafluorobenzyl ether, which was separated on a 10% Dexsil 300GC column and determined by the use of chinoform-d4 as an internal standard. The clean-up of chionoform in plasma and urine was efficiently achieved by extracting with benzene, while the drug in the tissue was pretreated successively by extraction with 12.5% v/v pyridine-benzene, separation on a Clin-Elut cartridge and adsorption on alumina. The quantitation limit of chinoform was 100 pg, and the recovery rates of chinoform added to plasma and tissue were 98% and 92%, respectively. The chinoform levels in biological fluids and tissues in dogs after prolonged administration of the drug at a dose of 400 mg/kg/day were measured by the proposed method. The plasma level and tissue distribution of chinoform are also discussed.

Determination of the partition coefficient and acid dissociation constants of iodochlorhydroxyquin by an improved partition method.

A simple and precise method for determining partition coefficients was developed utilizing a disposable injector. The method was used to determine the partition ratio of iodochlorhydroxyquin between n-decane and phosphate-buffered saline, pH 7.4. The partition ratio was found to be 1750 with a coefficient of variation of 3%. Moreover, it was found that iodochlorhydroxyquin did not associate in n-decane at a concentration less than 1 X 10(-3) M. The acid dissociation constants and the partition coefficient of the undissociated species were determined. These values corresponded well with the values obtained from spectrophotometric methods.

Reverse-phase high-performance liquid chromatographic determination of halogenated 8-hydroxyquinoline compounds in pharmaceuticals and bulk drugs.

A reverse-phase high-performance liquid chromatographic (HPLC) method was developed for determining iodochlorhydroxyquin, 5,7-dichloro-8-hydroxyquinoline, and 5,7-diiodo-8-hydroxyquinoline in creams, ointments, shampoos, tablets, and bulk drugs. A column packed with 10-micron phenyl-silica and a mobile phase of 0.001 M NiCl2 in acetonitrile-methanol-water (30:20:50) was used to separate the nickel complexes of the three drugs, with detection at 273 nm. Analysis of creams, ointments, shampoos, and tablets gave results close to the label declarations. Recovery of standard material added to samples was greater than or equal to 98%. Linearity of response was shown over a range of 30-150% of label claim for standards of the three drug substances. Multiple analyses of iodochlorhydroxyquin and diiodohydroxyquinoline bulk drugs showed purities of 99.96 and 98.77% with CV of 1.17 and 0.73%, respectively. The HPLC method offers an alternative to current USP procedures, which lack stability-indicating and specificity characteristics.

High-performance liquid chromatographic analysis of iodochlorhydroxyquin and hydrocortisone in ointments and creams.

A simple isocratic, high-performance liquid chromatographic (HPLC) assay procedure was developed for the simultaneous determination of iodochlorhydroxyquin and hydrocortisone in ointments and creams using phenyl salicylate as an internal standard. Ointment samples were extracted by direct dissolution in ether. Homogeneous suspensions of the creams were prepared in the mobile phase. The samples were spiked by the addition of standard iodochlorhydroxyquin, standard hydrocortisone, and the internal standard and subsequently extracted with the mobile phase. HPLC was performed using a reverse-phase microparticulate C-18 column, a precolumn, and a UV detector set at 256 nm. A mobile phase containing methanol and 0.05 M phosphoric acid (70:30) was employed at a flow rate of 1 ml/min. The percent iodochlorhydroxyquin and hydrocortisone found to be present in eight commercial products is reported.

Analysis of iodochlorhydroxyquin in biological materials by high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatographic system using a mobile phase of 0.05 M phosphoric acid--methanol (30:70) was developed for determination of iodochlorhydroxyquin (clioquinol, I) in biological material. I was extracted from samples with diethyl ether. Conjugates of I were hydrolyzed to free I and extracted by the same method. The ether phases were evaporated to dryness, reconstituted in the mobile phase and chromatographed using a microparticulate C18 column, a pre-column and a UV detector set at 256 nm. Quantitation of I in the range of 0.20-2.0 micrograms/ml of urine, 0.50-2.0 micrograms/g of liver, and 0.25-2.0 micrograms/g of feces was obtained with coefficients of variation of 0.02, 0.05, and 0.06, respectively. The detection limit of I was 0.2 micrograms. Extensive absorption of I upon topical application to dogs was also demonstrated.

Rapid method for the simultaneous analysis of hydrocortisone and clioquinol in topical preparations by high-performance liquid chromatography.

Reversed-phase high performance liquid chromatographic methods for the analysis of ointments containing hydrocortisone and clioquinol have been investigated. A successful method using a C18 column and methanol--0.05 M phosphoric acid (80:20) as eluting solvent has been developed which allows both compounds to be determined simultaneously. The high-performance liquid chromatographic procedure is rapid and sensitive whereas the assay described in the 1980 BP involves a different method for the analysis of each component of the ointment. The method has also been further applied to the analysis of ointments containing hydrocortisone combined with other halogenated hydroxyquinolines.

Analysis of iodochlorhydroxyquin in cream formulations and bulk drugs by high-performance liquid chromatography.

A high-performance liquid chromatographic method for the analysis of iodochlorhydroxyquin in creams and as bulk drugs has been developed. Iodochlorhydroxyquin was acetylated in the 8-position by reaction with acetic anhydride in pyridine. The resulting ester was mixed with the internal standard and chromatographed on a microparticulate silica column. Recovery was quantitative and the method was shown to be applicable to cream formulations from several manufacturers.