Synthesis, Structure, Anion Binding, And Sensing By Calix[4] Pyrrole Isomers

The synthesis, structure, and anion binding properties of chromogenic octamethylcalix[4] pyrroles (OMCPs) and their N-confused octamethylcalix[4] pyrrole isomers (NC-OMCPs) containing an inverted pyrrole ring connected via alpha\u27- and beta-positions are described. X-ray diffraction analyses proved the structures of two synthesized isomeric pairs of OMCPs and NC-OMCPs. The addition of anions to solutions of chromogenic OMCPs and NC-OMCPs resulted in different colors suggesting different anion-binding behaviors. The chromogenic NC-OMCPs showed significantly stronger anion-induced color changes compared to the corresponding chromogenic OMCP, and the absorption spectroscopy titrations indicated that chromogenic OMCPs and NC-OMCPs also possess different anion binding selectivity. Detailed NMR studies revealed that this rather unusual feature stems from a different anion-binding mode in OMCPs and NC-OMCPs, one where the beta-pyrrole C-H of the inverted pyrrole moiety participates in the hydrogen-bonded anion-NC-OMCP complex. Preliminary colorimetric microassays using synthesized chromogenic calixpyrroles embedded in partially hydrophilic polyurethane matrices allow for observation of analyte-specific changes in color when the anions are administered in the form of their aqueous solutions and in the presence of weakly competing anions

Evaluation of the suitability of ionic liquid-based liquid-liquid microextractions for blood protein removal

The analysis of biological samples, such as whole blood, comes with several sample preparation challenges. Biological matrices often contain a variety of endogenous components that can interfere with the determination of xenobiotics. Especially blood plasma proteins (e.g. serum albumin) are known to interfere with electrospray ionization and result in analyte ion suppression. Sample preparation techniques should guarantee adequate removal of these biomolecules. The current study aims to determine to which extent proteins are removed from whole blood samples, using ionic liquid-based dispersive liquid-liquid microextraction (IL-DLLME). A qualitative comparison of the protein presence in extracts of IL-DLLME, solid-phase extraction (SPE) and protein precipitation (PP) was performed, using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Additionally, UV/VIS spectrophotometry was used to determine the protein content of a whole blood sample and IL-DLLME, SPE and PP extracts of the same sample. Finally, a quantitative comparison of matrix effects of benzodiazepines present in both whole blood and water samples. SDS-PAGE results showed that IL-DLLME extracts still contained proteins (i.e. albumin, hemoglobin); however, band intensities were comparable to SPE extracts. Spectrophotometric tests showed a total protein content of approximately 2 mg/mL in the final extracts. PP showed the highest protein extraction rate (19 mg/mL). Quantitative ME results showed no significant differences (α = 0.05) between blood and water IL-DLLME extracts. Overall, this is the first study to conclude that IL-DLLME is able to sufficiently remove blood proteins from whole blood samples, in order to avoid significant ion suppression.</p

Development and validation of a fast ionic liquid-based dispersive liquid-liquid microextraction procedure combined with LC-MS/MS analysis for the quantification of benzodiazepines and benzodiazepine-like hypnotics in whole blood

To date, thorough clean-up of complex biological samples remains an essential part of the analytical process. The solid phase extraction (SPE) technique is the well-known standard, however, its main weaknesses are the labor-intensive and time-consuming protocols. In this respect, dispersive liquid-liquid microextractions (DLLME) seem to offer less complex and more efficient extraction procedures. Furthermore, ionic liquids (ILs) - liquid salts - are emerging as new promising extraction solvents, thanks to their non-flammable nature, negligible vapor pressure and easily adaptable physiochemical properties. In this study, we investigated whether ILs can be used as an extraction solvent in a DLLME procedure for the extraction of a broad range of benzodiazepines and benzodiazepine-like hypnotics in whole blood samples. 1.0mL whole blood was extracted using an optimized 30-min IL-based DLLME procedure, followed by LC-ESI(+)-MS/MS analysis in scheduled MRM scan mode. The optimized analytical method was successfully validated for 7-aminoflunitrazepam, alprazolam, bromazepam, clobazam, clonazepam, clotiazepam, diazepam, estazolam, ethyl loflazepate, etizolam, flurazepam, lormetazepam, midazolam, oxazepam, prazepam, temazepam, triazolam, zolpidem and zopiclone. The method showed good selectivity for endogenous interferences based on 12 sources of blank whole blood. No benzodiazepine interferences were observed, except for clorazepate and nordiazepam, which were excluded from the quantitative method. Matrix-matched calibration curves were constructed covering the whole therapeutic range, including low toxic plasma concentrations. Accuracy and precision results met the proposed acceptance criteria for the vast majority of compounds, except for brotizolam, chlordiazepoxide, cloxazolam, flunitrazepam, loprazolam, lorazepam and nitrazepam, which can only be determined in a semi-quantitative way. Recoveries were within the range of 24.7%-127.2% and matrix effects were within 20.0%-92.6%. Both parameters were tested using 5 sources of whole blood and coefficients of variance were below 20%. Overall, the applicability of ILs as promising solvents for the extraction of benzodiazepines in whole blood samples has been proven. Moreover, a fast and easy IL-based DLLME procedure was developed for the quantification of 19 benzodiazepines and benzodiazepine-like hypnotics.</p

Fast and easy extraction of antidepressants from whole blood using ionic liquids as extraction solvent

This study aims to prove that ionic liquids (ILs) can be used as extraction solvents in a liquid-liquid microextraction, coupled to LC-MS/MS, for the quantification of a large group of antidepressants in whole blood samples. The sample preparation procedure consisted of adding 1.0mL aqueous buffer pH 3.0 and 60µL of IL (1-butyl-3-methylimidazolium hexafluorophosphate) to 1.0mL whole blood. Subsequently, a 5-min rotary mixing step was performed followed by centrifugation. The lower IL phase was collected, diluted 1:10 in methanol and 10µL was injected into the LC-MS/MS. The following analytes were included in the full-quantitative method: agomelatine, amitriptyline, bupropion, clomipramine, dosulepin, doxepin, duloxetine, escitalopram, fluoxetine, imipramine, maprotiline, mianserin, mirtazapine, nortriptyline, paroxetine, reboxetine, trazodone and venlafaxine. Selectivity was checked for 10 different whole blood matrices. Additionally, possible interferences of deuterated standards or other antidepressants were evaluated. Overall, no interferences were found. For each analyte a matrix-matched calibration curve was constructed (7 levels, n = 6), covering therapeutic and low toxic concentrations. Accuracy and precision were evaluated over eight days, at three concentration levels (n = 2). Bias, repeatability and intermediate precision results met with the proposed validation criteria, except for fluvoxamine, which was therefore only included in the semi-quantitative method. LOQs were set at the lowest calibrator concentration and LOD values were - for most analytes - within a range of 1-2ng/mL. Recoveries (RE) and matrix effects (ME) were evaluated for five types of donor whole blood, at two concentration levels. RE values were within a range of 53.11-132.98%. ME values were within a range of 61.92-123.24%. In conclusion, this study proves the applicability of ILs as extraction solvents for a large group of antidepressants in complex whole blood matrices.</p

Effects of thiol substitution in deep-eutectic solvents (DESs) as solvents for metal oxides

This study deals with an investigation of how substitution of an alcohol group by a thiol group in mixtures of choline chloride with a series of bio-sourceable molecules affects the physico-chemical properties of the mixtures and their ability to dissolve metal oxides. All of the thiol mixtures studied showed a higher affinity and selectivity for late transition metals and the physical properties of the mixtures were improved compared to their alcohol analogues (i.e. lower viscosity, wider liquid range). The metal solubility was assessed via determination of the final concentration of the metal oxides dissolved in thiol mixtures via inductively coupled plasma optical emission spectroscopy (ICP-OES). The thiol function selectively improved the solubilities of the late transition metal oxides (i.e. copper and zinc), which are valuable metals often present as residue in industrial waste. The solubility of iron oxides was much lower than that of the valuable metals, which is a significant benefit in industrial applications. The different solubilization behaviour of metal oxides in the thiol and alcohol mixtures was further investigated via UV-vis absorption and infrared spectroscopy. This study allowed the potential of these deep-eutectic solvents for the selective recovery of metals to be assessed

Pronounced anti-proliferative activity and tumor cell selectivity of 5-alkyl-2-amino-3-methylcarboxylate thiophenes

5-(2-(4-Methoxyphenyl)ethyl)-2-amino-3-methylcarboxylate thiophene (TR560) is the prototype drug of a recently discovered novel class of tumor-selective compounds that preferentially inhibit the proliferation of specific tumor cell types (e.g. leukemia/lymphoma). Here, we further increased tumor selectivity by simplification of the molecule through replacing the 4-methoxyphenyl moiety by an alkyl chain. Several 2-amino-3-methylcarboxylate thiophene derivatives containing at C-5 an alkyl group consisting of at least 6 (hexyl) to 9 (nonyl) carbon units showed pronounced anti-proliferative activity in the mid-nanomolar range with 500- to 1000-fold tumor cell selectivity. The compounds preferentially inhibited the proliferation of T-lymphoma CEM and Molt/4, prostate PC-3, kidney Caki-1 and hepatoma Huh-7 tumor cells, but were virtually inactive against other tumor cell lines including B-lymphoma Raji and cervix carcinoma HeLa cells. The novel prototype drug 3j (containing a 5-heptyl chain) elicited a cytotoxic, rather than cytostatic activity, already after 4 h of exposure. The unusual tumor selectivity could not be explained by a differential uptake (or efflux) of the drug by sensitive versus resistant tumor cells. Exposure of a fluorescent derivative of 3j revealed pronounced uptake of the drug in the cytoplasm, no visible appearance in the nucleus, and a predominant localization in the endoplasmic reticulum. These observations may be helpful to narrow down the intracellular localization and identification of the molecular target of the 5-substituted thiophene derivatives. publisher: Elsevier articletitle: Pronounced anti-proliferative activity and tumor cell selectivity of 5-alkyl-2-amino-3-methylcarboxylate thiophenes journaltitle: European Journal of Medicinal Chemistry articlelink: http://dx.doi.org/10.1016/j.ejmech.2017.03.044 content_type: article copyright: © 2017 The Authors. Published by Elsevier Masson SAS. ispartof: European Journal of Medicinal Chemistry vol:132 pages:219-235 ispartof: location:France status: publishe

Alpha-carboxynucleoside phosphonates: direct-acting inhibitors of viral DNA polymerases

Acyclic nucleoside phosphonates represent a well-defined class of clinically used nucleoside analogs. All acyclic nucleoside phosphonates need intracellular phosphorylation before they can bind viral DNA polymerases. Recently, a novel class of alpha-carboxynucleoside phosphonates have been designed to mimic the natural 2′-deoxynucleotide 5′-triphosphate substrates of DNA polymerases. They contain a carboxyl group in the phosphonate moiety linked to the nucleobase through a cyclic or acyclic bridge. Alpha-carboxynucleoside phosphonates act as viral DNA polymerase inhibitors without any prior requirement of metabolic conversion. Selective inhibitory activity against retroviral reverse transcriptase and herpesvirus DNA polymerases have been demonstrated. These compounds have a unique mechanism of inhibition of viral DNA polymerases, and provide possibilities for further modifications to optimize and fine tune their antiviral DNA polymerase spectrum

Oxidation of monoterpenes catalysed by a water-soluble Mn(III) PEG-porphyrin in a biphasic medium

It is well established that the transformation of abundant and cheap natural products, such as terpenoids, can produce other more valuable compounds. Thymoquinone, which has a commercial value significantly higher than that of its precursors, can be obtained by oxidation of carvacrol and thymol. In this work, a new water-soluble Mn-III PEG-porphyrin is reported as catalyst in a water/hexane (1:1) biphasic medium for the oxidation of carvacrol and thymol into thymoquinone. The reactions were performed using tert-butyl hydroperoxide as oxidant in the presence of ammonium acetate as co-catalyst, reaching 94 and 78% of conversion after 5 h of reaction for thymol and carvacrol, respectively. Experiments with oregano essential oil as substrate revealed selective transformation of thymol and carvacrol into thymoquinone. The main advantage of this biphasic system based on a water-soluble catalyst and on substrates and products soluble in hexane, is the straightforward isolation, recovery and recycling of the catalyst by simple phase separation. Recycling studies of the Mn-III PEG-porphyrin using thymol as substrate showed high conversion values throughout four catalytic cycles

Artemisinin analogues as potent inhibitors of in vitro hepatitis C virus replication

We reported previously that Artemisinin (ART), a widely used anti-malarial drug, is an inhibitor of in vitro HCV subgenomic replicon replication. We here demonstrate that ART exerts its antiviral activity also in hepatoma cells infected with full length infectious HCV JFH-1. We identified a number of ART analogues that are up to 10-fold more potent and selective as in vitro inhibitors of HCV replication than ART. The iron donor Hemin only marginally potentiates the anti-HCV activity of ART in HCV-infected cultures. Carbon-centered radicals have been shown to be critical for the anti-malarial activity of ART. We demonstrate that carbon-centered radicals-trapping (the so-called TEMPO) compounds only marginally affect the anti-HCV activity of ART. This provides evidence that carbon-centered radicals are not the main effectors of the anti-HCV activity of the Artemisinin. ART and analogues may possibly exert their anti-HCV activity by the induction of reactive oxygen species (ROS). The combined anti-HCV activity of ART or its analogues with L-N-Acetylcysteine (L-NAC) [a molecule that inhibits ROS generation] was studied. L-NAC significantly reduced the in vitro anti-HCV activity of ART and derivatives. Taken together, the in vitro anti-HCV activity of ART and analogues can, at least in part, be explained by the induction of ROS; carbon-centered radicals may not be important in the anti-HCV effect of these molecules