34 results on '"Damjan Makuc"'
Search Results
2. Children gut microbiota exhibits a different composition and metabolic profile after in vitro exposure to Clostridioides difficile and increases its sporulation
- Author
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Sabina Horvat, Aleksander Mahnic, Damjan Makuc, Klemen Pečnik, Janez Plavec, and Maja Rupnik
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Microbiology (medical) ,Microbiology - Abstract
Clostridioides difficile (Clostridium difficile) infection (CDI) is one of the main public health concerns in adults, while children under 2 years of age are often colonized asymptomatically. In both adults and children, CDI is strongly associated with disturbances in gut microbiota. In this study, an in-vitro model of children gut microbiota was challenged with vegetative cells or a conditioned media of six different toxigenic C. difficile strains belonging to the ribotypes 027, 078, and 176. In the presence of C. difficile or conditioned medium the children gut microbiota diversity decreased and all main phyla (Bacteroidetes, Firmicutes, and Proteobacteria) were affected. The NMR metabolic spectra divided C. difficile exposed children gut microbiota into three clusters. The grouping correlated with nine metabolites (short chain fatty acids, ethanol, phenolic acids and tyramine). All strains were able to grow in the presence of children gut microbiota and showed a high sporulation rate of up to 57%. This high sporulation rate in combination with high asymptomatic carriage in children could contribute to the understanding of the reported role of children in C. difficile transmissions.
- Published
- 2022
3. Children gut microbiota exhibits a different composition and metabolic profile after
- Author
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Sabina, Horvat, Aleksander, Mahnic, Damjan, Makuc, Klemen, Pečnik, Janez, Plavec, and Maja, Rupnik
- Published
- 2022
4. Organic acid cross-linked 3D printed cellulose nanocomposite bioscaffolds with controlled porosity, mechanical strength, and biocompatibility
- Author
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Marco Beaumont, Armin Winter, Uroš Maver, Florian Lackner, Doris Bračič, Tamilselvan Mohan, Karin Stana Kleinschek, Rupert Kargl, Damjan Makuc, Andreja Dobaj Štiglic, Fazilet Gürer, Janez Plavec, Lidija Gradišnik, and Isabel Duarte
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History ,Multidisciplinary ,Materials science ,Nanocomposite ,Polymers and Plastics ,Biocompatibility ,Tissue Engineering ,technology, industry, and agriculture ,macromolecular substances ,Industrial and Manufacturing Engineering ,Carboxymethyl cellulose ,Biomaterials ,chemistry.chemical_compound ,Compressive strength ,Chemical engineering ,chemistry ,Tissue engineering ,medicine ,Business and International Management ,Cellulose ,Swelling ,medicine.symptom ,Citric acid ,medicine.drug - Abstract
Biocompatible polysaccharide scaffolds with controllable pore size, good mechanical properties and without hazardous chemical crosslinkers, are desirable for long-term tissue engineering applications but their production is highly challenging. Herein, we fabricated three-dimensional (3D) scaffolds using a polysaccharide composite ink composed of nanofibrillated cellulose, carboxymethyl cellulose and citric acid, featuring strong shear thinning behavior and adequate printability. Highly porous and mechanically stable scaffolds were produced by combining direct ink writing 3D printing, freeze-drying and dehydrothermal heat-assisted crosslinking techniques. The last heat-assisted step induces reaction of citric acid, which was chosen as it is a non-hazardous and green crosslinker. Degree of crosslinking was controlled by varying the concentration of citric acid (2.5 – 10 wt.%) to tune the chemical, surface, swelling and degradation properties of the scaffolds in the dry and hydrated states. The scaffolds with the highest porosity (86%) and interconnected pores (100-450 µm) were acquired using the lowest citric acid concentration; and the porosity was significantly reduced at higher citric acid concentration as well as at longer hydration time. The compressive strength, elastic modulus and the shape recovery behavior of the crosslinked scaffolds were increased significantly with increasing crosslinker concentration. The prepared crosslinked scaffolds promoted clustered cell adhesion and showed no cytotoxic effects, as determined by a cell viability assay and live/dead staining with human bone tissue derived osteoblast cells. The water-based and non-hazardous crosslinking method reported here can be extended to all polysaccharide-based materials to develop cell-friendly scaffolds with tailormade properties suitable for various tissue engineering applications in general.
- Published
- 2022
5. Water-based carbodiimide mediated synthesis of polysaccharide-amino acid conjugates: Deprotection, charge and structural analysis
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Rupert Kargl, Karin Stana Kleinschek, Damjan Makuc, Fazilet Gürer, Matej Bračič, Tamilselvan Mohan, Janez Plavec, and Martin Thonhofer
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Polymers and Plastics ,Glycine ,02 engineering and technology ,DEPT ,010402 general chemistry ,01 natural sciences ,Polysaccharide Conjugates ,chemistry.chemical_compound ,Carbodiimide ,Materials Chemistry ,Peptide bond ,Organic chemistry ,Deprotection Charges ,Solubility ,chemistry.chemical_classification ,Aqueous solution ,Molecular Structure ,Organic Chemistry ,Tryptophan ,021001 nanoscience & nanotechnology ,NMR ,0104 chemical sciences ,Amino acid ,Carbodiimides ,chemistry ,Ninhydrin ,Carboxymethylcellulose Sodium ,Amino acids ,Titration ,Indicators and Reagents ,0210 nano-technology - Abstract
We report here a one-step aqueous method for the synthesis of isolated and purified polysaccharide-amino acid conjugates. Two different types of amino acid esters: glycine methyl ester and L-tryptophan methyl ester, as model compounds for peptides, were conjugated to the polysaccharide carboxymethylcellulose (CMC) in water using carbodiimide at ambient conditions. Detailed and systematic pH-dependent charge titration and spectroscopy (infrared, nuclear magnetic resonance: 1H, 13C- DEPT 135, 1H- 13C HMBC/HSQC correlation), UV–vis, elemental and ninhydrin analysis provided solid and direct evidence for the successful conjugation of the amino acid esters to the CMC backbone via an amide bond. As the concentration of amino acid esters increased, a conjugation efficiency of 20–80% was achieved. Activated charcoal aided base-catalyzed deprotection of the methyl esters improved the solubility of the conjugates in water. The approach proposed in this work should have the potential to tailor the backbone of polysaccharides containing di- or tri-peptides.
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- 2021
- Full Text
- View/download PDF
6. Interference of oleamide with analytical and bioassay results
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Valentina Metličar, Janez Plavec, Damjan Makuc, Kurt Lucas, Anne Schink, Irena Vovk, Katerina Naumoska, and Urška Jug
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0301 basic medicine ,Sample handling ,Multidisciplinary ,Oleamide ,Chromatography ,Computer science ,Immunology ,lcsh:R ,010401 analytical chemistry ,lcsh:Medicine ,Interference (wave propagation) ,01 natural sciences ,Article ,0104 chemical sciences ,Chemistry ,03 medical and health sciences ,chemistry.chemical_compound ,030104 developmental biology ,chemistry ,Bioassay ,lcsh:Q ,Double check ,Sample preparation ,Plant sciences ,lcsh:Science - Abstract
During sample preparation and analysis, samples are coming in contact with different labware materials. By four unrelated analytical (phytochemical and pharmaceutical) case-studies and employing different analytical techniques, we demonstrated the potential misinterpretation of analytical results due to the use of contaminants-leaching labware during sample handling. Oleamide, a common polymer lubricant and a bioactive compound, was identified as a main analytical interference, leaching from different labware items into solvents, recognised as chemically compatible with the tested polymer material. Moreover, anti-inflammatory effect of oleamide at 100 μg mL−1 and considerable pro-inflammatory effect of the plastic syringe extractables (containing oleamide) at the same level were shown in a TLR4-based bioassay. Taking these results into account, together with the fact that oleamide can be a compound of natural origin, we would like to notify the professional public regarding the possible erroneous oleamide-related analytical and bioassay results due to the use of oleamide-leaching labware. Researchers are alerted to double check the real source of oleamide (labware or natural extract), which will prevent further reporting of false results. Analysis of procedural blanks with de-novo developed UHPLC-ESI-MS method is, among some other strategies, proposed for detection of oleamide interference and avoidance of misleading results of certain analyses.
- Published
- 2020
7. 1H NMR metabolomics of microbial metabolites in the four MW agricultural biogas plant reactors: A case study of inhibition mirroring the acute rumen acidosis symptoms
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Blaž Stres, Damjan Makuc, Boštjan Murovec, Sabina Kolbl Repinc, Domen Zavec, Zala Prevoršek, Robert Šket, Klemen Pečnik, and Janez Plavec
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0301 basic medicine ,Environmental Engineering ,Chemistry ,030106 microbiology ,Trimethylamine ,General Medicine ,Management, Monitoring, Policy and Law ,equipment and supplies ,03 medical and health sciences ,Rumen ,chemistry.chemical_compound ,030104 developmental biology ,Metabolomics ,Biogas ,medicine ,Metabolome ,Food science ,Pyruvic acid ,medicine.symptom ,Waste Management and Disposal ,Acidosis ,Mesophile - Abstract
In this study, nuclear magnetic resonance (1H NMR) spectroscopic profiling was used to provide a more comprehensive view of microbial metabolites associated with poor reactor performance in a full-scale 4 MW mesophilic agricultural biogas plant under fully operational and also under inhibited conditions. Multivariate analyses were used to assess the significance of differences between reactors whereas artificial neural networks (ANN) were used to identify the key metabolites responsible for inhibition and their network of interaction. Based on the results of nm-MDS ordination the subsamples of each reactor were similar, but not identical, despite homogenization of the full-scale reactors before sampling. Hence, a certain extent of variability due to the size of the system under analysis was transferred into metabolome analysis. Multivariate analysis showed that fully active reactors were clustered separately from those containing inhibited reactor metabolites and were significantly different. Furthermore, the three distinct inhibited states were significantly different from each other. The inhibited metabolomes were enriched in acetate, caprylate, trimethylamine, thymine, pyruvate, alanine, xanthine and succinate. The differences in the metabolic fingerprint between inactive and fully active reactors observed in this study resembled closely the metabolites differentiating the (sub) acute rumen acidosis inflicted and healthy rumen metabolomes, creating thus favorable conditions for the growth and activity of pathogenic bacteria. The consistency of our data with those reported before for rumen ecosystems shows that 1H NMR based metabolomics is a reliable approach for the evaluation of metabolic events at full-scale biogas reactors.
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- 2018
8. High selectivity of thin-layer chromatography enables characterization of physalin L standard and its impurity
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Irena Vovk, Alen Albreht, Damjan Makuc, Eva Kranjc, and Vesna Glavnik
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Chromatography ,010405 organic chemistry ,Silica gel ,010401 analytical chemistry ,Clinical Biochemistry ,Sulfuric acid ,Mass spectrometry ,01 natural sciences ,Biochemistry ,Thin-layer chromatography ,0104 chemical sciences ,Analytical Chemistry ,chemistry.chemical_compound ,chemistry ,Impurity ,Reagent ,Derivatization ,Densitometry - Abstract
High-performance thin-layer chromatography (HPTLC) is a powerful separation technique which is often overlooked. In this study, we comprehensively assessed the applicability, ease, and performance of HPTLC in combination with densitometry and mass spectrometry (MS) to characterize physalins — relatively polar secondary metabolites from Physalis alkekengi L. HPTLC silica gel plates were evaluated in combination with 14 developing solvents (13 published in the literature). Bonded stationary phases (HPTLC RP-18, RP-18 W, CN F254S) were also tested. Four detection reagents (sulfuric acid, anisaldehyde, 4-dimethylaminocinnamaldehyde (DMACA), and molybdatophosphoric acid) were compared to ascertain which one is the most suitable. For all chromatographic analyses, a commercial standard physalin L and a P. alkekengi L. crude extract were used. In some cases, physalin L standard appeared as two clearly resolved bands on silica plates, but only after derivatization, where sulfuric acid reagent provided the best sel...
- Published
- 2017
9. Water-Soluble Colorimetric Amino[bis(ethanesulfonate)] Azobenzene pH Indicators: A UV–Vis Absorption, DFT, and 1H–15N NMR Spectroscopy Study
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Konrad Szaciłowski, Maria A. Cardona, Janez Plavec, Damjan Makuc, and David C. Magri
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General Chemical Engineering ,Metal ions in aqueous solution ,Protonation ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Medicinal chemistry ,Article ,Acid dissociation constant ,lcsh:Chemistry ,chemistry.chemical_compound ,Charge transfer ,pH indicator ,010405 organic chemistry ,Chemistry ,Molecules -- Research ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,Binding constant ,Indicators and test-papers ,3. Good health ,0104 chemical sciences ,lcsh:QD1-999 ,Azobenzene ,Selectivity ,Analytical chemistry - Abstract
Water-soluble azobenzene derivatives containing amino[bis(ethanesulfonate)] groups are demonstrated as colorful pH indicators in water and on filter paper. Vibrant color changes were observed from yellow/orange to pink between pH 1 and 4, which are attributed to an intramolecular charge-transfer mechanism. The pKas of the indicators range from 2.1 to 2.6. 1H/1H–15N NMR studies in deuterium oxide reveal that the protonation of the azobenzene pH indicators occurs predominantly at the β-azo nitrogen atom, in agreement with the density functional theory calculations. Excellent selectivity for protons was confirmed in water over common biologically relevant metal ions. Studies in methanol, however, indicate that the pH indicator with a methoxy group ortho to the amino[bis(ethanesulfonate)] group facilitates the selective coordination of Cu2+ with a binding constant pβCu2+ of 4.6 ± 0.1. The indicators complement the existing library of azobenzene indicator dyes and may be useful for measuring the environmental pH at higher proton concentrations., peer-reviewed
- Published
- 2017
10. Probing the Effects of Pyrimidine Functional Group Switches on Acyclic Fleximer Analogues for Antiviral Activity
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Christina F. Spiropoulou, Payel Chatterjee, Janez Plavec, Katherine L. Seley-Radtke, Yafet Arefeayne, Mike Flint, Mary K. Yates, and Damjan Makuc
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filovirus ,Pyrimidine ,viruses ,Proton Magnetic Resonance Spectroscopy ,Molecular Conformation ,Pharmaceutical Science ,nucleoside ,medicine.disease_cause ,fleximers ,01 natural sciences ,Antiviral Agents ,Virus ,Article ,Analytical Chemistry ,Dengue fever ,lcsh:QD241-441 ,03 medical and health sciences ,chemistry.chemical_compound ,Structure-Activity Relationship ,lcsh:Organic chemistry ,flavivirus ,Cell Line, Tumor ,Drug Discovery ,medicine ,Structure–activity relationship ,Humans ,Physical and Theoretical Chemistry ,030304 developmental biology ,0303 health sciences ,Ebola virus ,biology ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,biology.organism_classification ,medicine.disease ,Ebolavirus ,Virology ,Lipids ,0104 chemical sciences ,3. Good health ,Enzyme binding ,Flavivirus ,Pyrimidines ,Chemistry (miscellaneous) ,Molecular Medicine ,Indicators and Reagents ,Nucleoside ,SAR - Abstract
Due to their ability to inhibit viral DNA or RNA replication, nucleoside analogues have been used for decades as potent antiviral therapeutics. However, one of the major limitations of nucleoside analogues is the development of antiviral resistance. In that regard, flexible nucleoside analogues known as &ldquo, fleximers&rdquo, have garnered attention over the years due to their ability to survey different amino acids in enzyme binding sites, thus overcoming the potential development of antiviral resistance. Acyclic fleximers have previously demonstrated antiviral activity against numerous viruses including Middle East Respiratory Syndrome coronavirus (MERS-CoV), Ebola virus (EBOV), and, most recently, flaviviruses such as Dengue (DENV) and Yellow Fever Virus (YFV). Due to these interesting results, a Structure Activity Relationship (SAR) study was pursued in order to analyze the effect of the pyrimidine functional group and acyl protecting group on antiviral activity, cytotoxicity, and conformation. The results of those studies are presented herein.
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- 2019
11. Synthesis and spectroscopic studies of diaza-8-crown-4-dinitrophenyl ethers
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Damjan Makuc, Konrad Szaciłowski, David C. Magri, Claudia Galea, and Janez Plavec
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chemistry.chemical_compound ,010405 organic chemistry ,Chemistry ,Crown (botany) ,Dinitrophenyl ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences - Abstract
The macrocycles 3,7-bis(3-nitrophenyl)-1,5,3,7-dioxadiazocane 1 and 3,7-bis(4-nitrophenyl)-1,5,3,7-dioxadiazocane 2 were synthesised by a one-pot reaction with substituted nitroanilines and formaldehyde under acidic conditions. The same reaction with 2-nitroaniline yielded N, N’-(oxybis(methylene))bis(2-nitroaniline) 3 rather than 3,7-bis(2-nitrophenyl)-1,5,3,7-dioxadiazocane 4. The yellow powders 1–3 were characterised by 1H/13C/15N NMR, FTIR and HRMS. The photophysical properties were studied by UV-visible absorption and steady-state fluorescence spectroscopy. Acid dissociation constants were determined by UV-visible absorption titrations in 1:1 (v/v) acetonitrile/water to be 0.80 and 3.1 for the meta- and para-substituted compounds 1 and 2, respectively. Compounds 1 and 2 were discovered to fluoresce in the solid-state, yellow and green, respectively, but not in solution. Density functional theory (DFT) calculations for 1–4 provide insight into the frontier molecular orbital energy levels. These compounds represent a new class of fluorescent heterocyclic building blocks for organic and supramolecular applications.
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- 2019
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12. Off-line multidimensional high performance thin-layer chromatography for fractionation of Japanese knotweed rhizome bark extract and isolation of flavan-3-ols, proanthocyanidins and anthraquinones
- Author
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Katerina Naumoska, Irena Vovk, Damjan Makuc, Vesna Glavnik, and Urška Jug
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010402 general chemistry ,01 natural sciences ,Biochemistry ,Analytical Chemistry ,chemistry.chemical_compound ,Flavan ,Fallopia japonica ,Taxifolin ,Proanthocyanidins ,High performance thin layer chromatography ,Procyanidin B3 ,Procyanidin B1 ,Procyanidin B2 ,Chromatography, High Pressure Liquid ,Flavonoids ,Chromatography ,Plant Extracts ,010401 analytical chemistry ,Organic Chemistry ,General Medicine ,0104 chemical sciences ,chemistry ,visual_art ,Plant Bark ,visual_art.visual_art_medium ,Bark ,Chromatography, Thin Layer ,Emodin ,Rhizome - Abstract
A methodology based on off-line multidimensional thin-layer chromatography was developed for isolation of several secondary metabolites from bark of Japanese knotweed (Fallopia japonica Houtt.) rhizomes. Successive fractionation steps using PLC silica gel and HPTLC silica gel or HPTLC cellulose plates in combination with various developing solvents enabled isolation of (+)-catechin, (-)-epicatechin, (-)-epicatechin gallate, procyanidin B1, procyanidin B2, procyanidin B3, proanthocyanidin B dimer gallate, emodin, emodin-8-O-glucoside and emodin-8-O-malonyl-glucoside. Their identity was confirmed by HPTLC, HPTLC-MSn and for most of them also by 1H NMR and 2D NMR analyses. To the best of our knowledge emodin-8-O-malonyl-glucoside, procyanidins B1 and B2 were for the first time isolated from this plant material. HPTLC and HPTLC-MSn analyses were also performed as support of fractionation/isolation process, leading to first detection of some compounds in bark of Japanese knotweed rhizomes and Japanese knotweed rhizomes in general: procyanidins B1 and B2, methyl derivatives of emodin bianthrone and emodin bianthrone-hexose, resveratrol-malonyl-hexoside and taxifolin derivatives. Characterization of flavan-3-ols and proanthocyanidins was facilitated by post-chromatographic derivatization of the corresponding chromatographic zones with 4-dimethylaminocinnamaldehyde (DMACA) detection reagent.
- Published
- 2021
13. Conformational NMR Study of Bistriazolyl Anion Receptors
- Author
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Wim Dehaen, Damjan Makuc, Janez Plavec, and Tamara Merckx
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Anions ,Models, Molecular ,Magnetic Resonance Spectroscopy ,anion receptors ,Protein Conformation ,Stereochemistry ,Thio ,Receptors, Cell Surface ,Crystallography, X-Ray ,010402 general chemistry ,01 natural sciences ,lcsh:Chemistry ,chemistry.chemical_compound ,NMR spectroscopy ,Pyridine ,Molecule ,010405 organic chemistry ,Chemistry ,Hydrogen bond ,host–guest systems ,conformational analysis ,Nuclear magnetic resonance spectroscopy ,Triazoles ,0104 chemical sciences ,lcsh:QD1-999 ,Heteronuclear molecule ,Proton NMR ,Two-dimensional nuclear magnetic resonance spectroscopy - Abstract
Conformational features of pyridine- and pyrimidine-based bistriazolyl anion receptors dissolved in acetonitrile-d3 were assessed by multidimensional, heteronuclear NMR spectroscopy. NOESY correlation signals suggested preorganization of both host molecules in solution in the absence of anions. In addition, only a single set of signals was observed in the 1H NMR spectra, which suggested a symmetrical conformation of anion receptors or their conformational exchange that is fast on the NMR time-scale. Furthermore, the predominant conformations of the pyridine- and pyrimidine-based anion receptors are preserved upon addition of chloride, bromide, and acetate anions. Chemical shift changes observed upon addition of anions showed that the NH (thio)urea and triazole protons are involved in anion-receptor interactions through hydrogen bonding.
- Published
- 2016
14. Colorimetric Naphthalene-Based Thiosemicarbazide Anion Chemosensors with an Internal Charge Transfer Mechanism
- Author
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Damjan Makuc, Kristina N. Farrugia, Konrad Szaciłowski, Janez Plavec, David C. Magri, and Agnieszka Podborska
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010405 organic chemistry ,Organic Chemistry ,Inorganic chemistry ,Nuclear magnetic resonance spectroscopy ,010402 general chemistry ,01 natural sciences ,Chloride ,Fluorescence spectroscopy ,0104 chemical sciences ,chemistry.chemical_compound ,Deprotonation ,chemistry ,Polymer chemistry ,medicine ,Physical and Theoretical Chemistry ,Methylene ,Anion binding ,Acetonitrile ,Naphthalene ,medicine.drug - Abstract
A series of thiosemicarbazide anion chemosensors substituted with naphthalene and 4-nitrophenyl or phenyl units were synthesized. The molecules were characterized by using 1H,13C DEPT and 15N NMR spectroscopy. The anion binding properties of compounds 1–4 were investigated by UV/Vis absorption and fluorescence spectroscopy in DMSO, DMSO/H2O (9:1 v/v), and acetonitrile with hydroxide, fluoride, acetate, hypophosphate, and chloride anions. Striking color changes were observed with nitro-containing chemosensors 2–4 with all anions, with the exception of chloride, which was attributed to an internal charge-transfer mechanism. 1H/13C/15N NMR titration studies and DFT and charge distribution calculations support a mechanism involving deprotonation of the central N–H bond. Compound 4 with a methylene spacer between the naphthalene and thiosemicarbazide moieties was deliberately designed as a fluorescent photoinduced electron-transfer anion (PET) sensor. However, the methylene spacer did not prevent delocalization of the HOMO orbital between the planar aromatic ring and the thiosemicarbazide unit as expected on the basis of the “fluorophore–spacer–receptor” PET model.
- Published
- 2016
15. Novel halogenated 3-deazapurine, 7-deazapurine and alkylated 9-deazapurine derivatives of l-ascorbic or imino-l-ascorbic acid: Synthesis, antitumour and antiviral activity evaluations
- Author
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Karlo Wittine, Damjan Makuc, Krešimir Pavelić, Robert Snoeck, Sandra Kraljević Pavelić, Dominique Schols, Janez Plavec, Graciela Andrei, Mladen Mintas, Maja Stipković Babić, and Tamara Martinović
- Subjects
Cytostatic activity ,Stereochemistry ,Cytomegalovirus ,Antineoplastic Agents ,Imino-l-ascorbic acid ,Ascorbic Acid ,Microbial Sensitivity Tests ,Antiviral Agents ,Article ,Cell Line ,HeLa ,Mice ,Structure-Activity Relationship ,3-Deazapurines ,7-Deazapurines ,9-Deazapurines ,L-Ascorbic acid ,Imino-L-ascorbic acid ,Antiviral activity ,Drug Discovery ,Animals ,Humans ,l-Ascorbic acid ,Structure–activity relationship ,IC50 ,Cell Proliferation ,Pharmacology ,Dose-Response Relationship, Drug ,Molecular Structure ,biology ,Cell growth ,Chemistry ,Organic Chemistry ,Biological activity ,General Medicine ,Fibroblasts ,Ascorbic acid ,biology.organism_classification ,In vitro ,Purines ,Cell culture ,Drug Screening Assays, Antitumor - Abstract
Keeping the potential synergy of biological activity of synthetic anomalous derivatives of deazapurines and l-ascorbic acid (l-AA) in mind, we have synthesized new 3-, 7- and 9-deazapurine derivatives of l-ascorbic (1–4, 8–10, 13–15) and imino-l-ascorbic acid (5–7, 11, 12, 16–19). These novel compounds were evaluated for their cytostatic and antiviral activity in vitro against a panel of human malignant tumour cell lines and normal murine fibroblasts (3T3). Among all evaluated compounds, the 9-deazapurine derivative of l-AA (13) exerted the most potent inhibitory activity on the growth of CEM/0 cells (IC50 = 4.1 ± 1.8 μM) and strong antiproliferative effect against L1210/0 (IC50 = 4.7 ± 0.1 μM) while the 9-deazahypoxanthine derivative of l-AA (15) showed the best effect against HeLa cells (IC50 = 5.6 ± 1.3 μM) and prominent effect on L1210/0 (IC50 = 4.5 ± 0.5 μM). Furthermore, the 9-deazapurine derivative disubstituted with two imino-l-AA moieties (18) showed the best activity against L1210/0 tumour cells (IC50 = 4.4 ± 0.3 μM) and the most pronounced antiproliferative effects against MiaPaCa-2 cells (IC50 = 5.7 ± 0.2 μM). All these compounds showed selective cytostatic effect on tumour cell lines in comparison with embryonal murine fibroblasts (3T3). When evaluating their antiviral activity, the 3-deazapurine derivative of l-AA (3) exhibited the highest activity against both laboratory-adapted strains of human cytomegalovirus (HCMV) (AD-169 and Davis) with EC50 values comparable to those of the well-known anti-HCMV drug ganciclovir and without cytotoxic effects on normal human embryonal lung (HEL) cells., Graphical abstract, Highlights • Deazapurine derivatives of l-ascorbic and imino-l-ascorbic acid were synthesized. • Compound 13 exerted strong activity on the growth of CEM/0 and L1210/0 cells. • Compound 15 showed the best cytostatic effect against HeLa cells. • Compound 18 showed the best cytostatic activity against L1210/0 and MiaPaCa-2. • Compound 3 exhibited highest effect against HCMV comparable to ganciclovir.
- Published
- 2015
16. One-pot click synthesis of 1,2,3-triazole-embedded unsaturated uracil derivatives and hybrids of 1,5- and 2,5-disubstituted tetrazoles and pyrimidines
- Author
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Janez Plavec, Damjan Makuc, Svjetlana Krištafor, Tamara Martinović, Sandra Kraljević Pavelić, Silvana Raić-Malić, and Andrea Bistrović
- Subjects
Antitumor activity ,1,2,3-Triazole ,Pyrimidine ,Organic Chemistry ,Uracil ,Biochemistry ,Combinatorial chemistry ,1, 2, 3-Triazoles ,1, 5- and 2, 5-disubstituted tetrazoles ,Click chemistry ,One-pot ,chemistry.chemical_compound ,chemistry ,Drug Discovery ,Microwave irradiation ,Organic chemistry - Abstract
Novel conformationally restricted pyrimidine derivatives with a 1,2,3-triazolyl scaffold bound via Z- and E-2-butenyl spacers were prepared by Cu(I)-catalyzed click chemistry via a one-pot, multi-step reaction under microwave irradiation, while 1,5- and 2,5-disubstituted tetrazoles were synthesized by convenient, environmentally friendly click synthesis and subsequently by N-alkylation of 5-substituted 1H-tetrazoles. Among all the tested compounds, the N-1,N-3-disubstituted olefinic uracil derivative showed the highest antiproliferative effects.
- Published
- 2015
17. A Kinetic Approach in the Evaluation of Radical-Scavenging Efficiency of Sinapic Acid and Its Derivatives
- Author
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Helena Abramovič, Tomaž Polak, Nataša Poklar Ulrih, Damjan Makuc, and Neda Nićiforović
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Coumaric Acids ,Radical ,Pharmaceutical Science ,antioxidant activity ,organske kisline ,Medicinal chemistry ,Syringaldehyde ,sinapinske kisline ,Article ,Analytical Chemistry ,lcsh:QD241-441 ,chemistry.chemical_compound ,0404 agricultural biotechnology ,lcsh:Organic chemistry ,radical scavenging kinetics ,Drug Discovery ,Sinapine ,Organic chemistry ,sinapic acid ,Physical and Theoretical Chemistry ,Scavenging ,udc:577.1:547.587.53 ,sinapin ,Organic Chemistry ,04 agricultural and veterinary sciences ,Free Radical Scavengers ,Syringic acid ,fenolne kisline ,040401 food science ,antioksidativna učinkovitost ,Kinetics ,radical scavenging mechanisms ,chemistry ,Chemistry (miscellaneous) ,Sinapic acid ,Endpoint Determination ,Emulsion ,Molecular Medicine ,lovilci prostih radikalov ,DPPH - Abstract
A kinetic approach was used to determine the radical scavenging activities of sinapic acid and its derivatives: sinapine, 4-vinylsyringol, syringic acid, syringaldehyde, and ethyl, propyl and butyl sinapate. The responses were expressed as rates of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH$^·$) scavenging (R$_S$), superoxide radical (O$_2$$^{·−}$) scavenging (R$_{FF}$), and β-carotene bleaching in the emulsion system (R$_B$). For R$_S$ and R$_B$, the esters of sinapic acid showed the highest responses while, for R$_{FF}$, this was seen for syringic acid. The effectiveness of the selected compounds for scavenging these free radicals was also determined at a fixed endpoint. The early response parameters were demonstrated to be good discriminators in assessing differences for antioxidants with comparable fixed endpoint activity. The primary feature that ranks the kinetic data and the endpoint determinations is interpreted in terms of the mechanisms of the reactions involved in each of the assays conducted.
- Published
- 2017
18. Conformational Analysis of Geometric Isomers of Pitavastatin Together with Their Lactonized Analogues
- Author
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Damjan Makuc, Janez Plavec, Jan Fabris, and Zdenko Časar
- Subjects
Magnetic Resonance Spectroscopy ,Double bond ,Stereochemistry ,Molecular Conformation ,Pharmaceutical Science ,010402 general chemistry ,01 natural sciences ,Article ,Analytical Chemistry ,super-statins ,Computational chemistry ,Ab initio quantum chemistry methods ,Drug Discovery ,medicine ,Single bond ,NMR studies ,Physical and Theoretical Chemistry ,barriers to rotation ,Pitavastatin ,Conformational isomerism ,chemistry.chemical_classification ,Atropisomer ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,conformational analysis ,Nuclear magnetic resonance spectroscopy ,0104 chemical sciences ,intramolecular dynamics ,Chemistry (miscellaneous) ,Quinolines ,Thermodynamics ,Molecular Medicine ,Cis–trans isomerism ,medicine.drug - Abstract
Super-statins are synthetic inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, which is the rate-limiting enzyme responsible for the biosynthesis of cholesterol. All of the super-statins with a C=C double bond spacer between the heterocyclic and the dihydroxycarboxylic moiety that are currently on the market exist as E-isomers. To extend the understanding of conformational and thermodynamic preferences of Z-isomeric super-statin analogues, this study focused on analyzing pitavastatin and its lactonized derivatives via NMR spectroscopy and ab initio calculations. Z-isomeric pitavastatin analogues exist in solution as a pair of interconverting rotamers, where the Gibbs free energies between the major and minor rotamers are within 0.12 and 0.25 kcal mol−1 and the rotational energy barriers are between 15.0 and 15.9 kcal mol−1. The analysis of long-range coupling constants and ab initio calculations revealed that rotation across the C5'–C7 single bond is essential for generating a pair of atropisomers. The overall comparison of the results between Z-isomeric pitavastatin and rosuvastatin analogues demonstrated that the former are to some extent more flexible to attain numerous conformations. Demonstrating how structural differences between super-statin analogues induce distinctive conformational preferences provides important insight into the super-statins’ conformational variability and may well improve future drug design.
- Published
- 2013
19. Conformational analysis of E/Z-isomeric pairs of rosuvastatin and its lactonized analogues
- Author
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Janez Plavec, Jan Fabris, Zdenko Časar, and Damjan Makuc
- Subjects
chemistry.chemical_classification ,Double bond ,010405 organic chemistry ,Stereochemistry ,Organic Chemistry ,nutritional and metabolic diseases ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Spectral line ,3. Good health ,0104 chemical sciences ,Enzyme ,chemistry ,Drug Discovery ,medicine ,Proton NMR ,Rosuvastatin ,Binding site ,Conformational isomerism ,Resonance line ,medicine.drug - Abstract
Most of the super-statins contain a CC double bond spacer between the heterocyclic and the chiral dihydroxycarboxylic moieties. The known drugs are E-geometric isomers, whereas very little is known about their Z-isomeric analogues. This study explains the unusual resonance line broadening observed in 1H NMR spectra of Z-isomeric rosuvastatin analogues at room temperature, which originates from dynamic exchange between different conformers. Conformational equilibria and intrinsic preferences of Z-isomeric rosuvastatin analogues provide valuable insight into conformational variability that is important for studying potential interactions within the binding site of the enzyme.
- Published
- 2013
20. Synergistic complex from plants Solanaceae exhibits cytotoxicity for the human hepatocellular carcinoma cell line HepG2
- Author
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Urban Švajger, Irena Vovk, Mitja Križman, Romina Schwarzlin, Nika Pušenjak, Janez Plavec, and Damjan Makuc
- Subjects
0301 basic medicine ,Carcinoma, Hepatocellular ,Cell Survival ,chemistry.chemical_element ,Antineoplastic Agents ,Apoptosis ,Cellobiose ,High-performance liquid chromatography ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Humans ,Cytotoxicity ,Solanaceae ,Traditional medicine ,biology ,Plant Extracts ,Liver Neoplasms ,food and beverages ,Drug Synergism ,General Medicine ,Hep G2 Cells ,Ascorbic acid ,biology.organism_classification ,030104 developmental biology ,chemistry ,Biochemistry ,Complementary and alternative medicine ,Cell culture ,030220 oncology & carcinogenesis ,Selenium ,Research Article - Abstract
Background It had been demonstrated that sugars from various plants can act as potent agents, which induce apoptosis of cancer cells. Methods Using HPLC, we fractionated a mixture of two plant extracts from the plant family Solanaceae, namely Capsicum chinense and the plant family Amaryllidaceae namely Allium sativum. We evaluated the effect of different fractions on apoptosis of HepG2 cell line. The most effective fraction was further studied to determine its molecular composition using mass spectrometry (MS) and NMR. We further evaluated the effect of determined molecular composition found in the selected fraction by using a mixture of commercially available substances, which were found in the fraction and tested its pro-apoptotic effect on HepG2 cells. To get some insight into potential apoptotic mechanisms we studied caspase-3 activity and mitochondrial integrity in treated cells. Results Out of 93 fractions obtained by HPLC from the plant extract we found HPLC fraction 10 (10 min elution) was the most effective. MS and NMR studies revealed high presence of cellobiose together with vitamin C, sulphur (S) and trace amounts of selenium (Se). HPLC fraction 10 triggered apoptosis of HepG2 within 3 h in the 0.01–1.0 mg/mL concentration range. Furthermore, a mixture of pure cellobiose, vitamin C, S and Se (complex cellobiose/C/S/Se) had a very similar capacity in inducing apoptosis of HepG2 cells compared to HPLC fraction 10. Complex cellobiose/C/S/Se was capable of inducing caspase-3 activity and led to loss of mitochondrial integrity. The capacity of cellobiose alone to induce apoptosis of HepG2 was approximately 1000-fold lower compared to complex cellobiose/C/S/Se. Conclusion In this study we present the highly synergistic effect of a unique complex consisting of cellobiose, vitamin C, sulphur and selenium on triggering the apoptosis of human hepatocellular carcinoma (HepG2) cell line.
- Published
- 2016
21. Novel 1,2,4-triazole and imidazole derivatives of l-ascorbic and imino-ascorbic acid: Synthesis, anti-HCV and antitumor activity evaluations
- Author
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Mirela Sedić, Mladen Mintas, Damjan Makuc, Karlo Wittine, Sandra Kraljević Pavelić, Krešimir Pavelić, Jan Balzarini, Maja Stipković Babić, Janez Plavec, Johan Neyts, and Pieter Leyssen
- Subjects
Magnetic Resonance Spectroscopy ,Clinical Biochemistry ,Drug Evaluation, Preclinical ,Pharmaceutical Science ,Antineoplastic Agents ,Ascorbic Acid ,Hepacivirus ,Pharmacology ,Virus Replication ,Antiviral Agents ,Biochemistry ,Virus ,Dogs ,IMP Dehydrogenase ,IMP dehydrogenase ,Cell Line, Tumor ,Drug Discovery ,Animals ,Humans ,Molecular Biology ,chemistry.chemical_classification ,Molecular Structure ,Cell growth ,Chemistry ,Organic Chemistry ,Imidazoles ,Biological activity ,Fibroblasts ,Triazoles ,Ascorbic acid ,Enzyme ,2 ,4-triazole ,imidazole ,L-ascorbic acid ,anti-HCV activity ,antitumor activity ,IMPDH ,Viral replication ,Cell culture ,Molecular Medicine ,Drug Screening Assays, Antitumor - Abstract
Several novel 1,2,4-triazole and imidazole L-ascorbic acid (1, 2, 3, 5, 6 and 9) and imino-ascorbic acid (4, 7 and 8) derivatives were prepared and evaluated for their inhibitory activity against hepatitis C virus (HCV) replication and human tumour cell proliferation. Compounds 6 and 9 exerted the most pronounced cytostatic effects in all tumour cell lines tested, and were highly selective for human T-cell acute lymphoblastic leukaemia cells (CEM/0) with IC(50)s of 10 ± 4 and 7.3 ± 0.1 μM, respectively. Unlike compound 9, compound 6 showed no toxicity in human diploid fibroblasts. One of the possible mechanisms of action of compound 6 accounting for observed cytostatic activity towards haematological malignancies might be inhibition of inosine monophosphate dehydrogenase (IMPDH) activity, a key enzyme of de novo purine nucleotide biosynthesis providing the cells with precursors for DNA and RNA synthesis indispensable for cell growth and division, which has emerged as an important target for antileukemic therapy. In addition, this compound proved to be the most potent inhibitor of the hepatitis C virus replication as well. However, observed antiviral effect was most likely associated with the effect that the compound exerted on the host cell rather than with selective effect on the replication of the virus itself. In conclusion, results of this study put forward compound 6 as a potential novel antitumor agent (IMPDH inhibitor) for treating leukaemia. Its significant biological activity and low toxicity in human diploid fibroblasts encourage further development of this compound as a lead.
- Published
- 2012
22. The occurrence and characterisation of phenolic compounds in Camelina sativa seed, cake and oil
- Author
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Nataša Poklar Ulrih, Tomaž Polak, Petra Terpinc, Damjan Makuc, and Helena Abramovič
- Subjects
Metal chelating activity ,Hydroxybenzoic acid ,biology ,Camelina sativa ,General Medicine ,biology.organism_classification ,Camelina ,Protocatechuic acid ,Analytical Chemistry ,chemistry.chemical_compound ,chemistry ,Biochemistry ,Sinapine ,Food science ,Salicylic acid ,Food Science ,Ellagic acid - Abstract
In this study, the antioxidant activities of Camelina sativa methanolic extracts were evaluated by different chemical assays: reducing power, 2,2-diphenyl-1-picrylhydrazyl (DPPH·) assay, the β-carotene bleaching method and the metal chelating activity assay. An LC–MS profiling method was used for a comprehensive study of the phenolic compounds and their representation in camelina seeds, cake and oil. For this purpose, 4-vinyl derivatives of hydroxycinnamic acids were synthesized by thermal decarboxylation of the corresponding phenolic acids and sinapine was isolated from kale ( Brassica oleracea ) applying a new method and confirmed by NMR. The results revealed that besides the total phenolic content and antioxidant activity, seeds and cake also possess a similar phenolic profile. In addition to sinapine and 4-vinyl derivatives, other antioxidants were successfully identified: ellagic acid, protocatechuic acid, p -hydroxybenzoic acid, sinapic acid, salicylic acid, catechin, rutin, quercetin and quercetin glucoside. Since after oil pressing most of the phenolic compounds remain in the seed residues, only a few compounds were identified in the oil. Camelina cake was found to have the best reducing power and radical scavenging activity, whereas camelina oil, with a relatively low phenolic content, exhibited the highest iron-chelating capacity and the best inhibitory action against β-carotene discolouration in an emulsified system.
- Published
- 2012
23. Non-targeted chromatographic analyses of cuticular wax flavonoids from Physalis alkekengi L
- Author
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Janez Plavec, Irena Vovk, Alen Albreht, Eva Kranjc, and Damjan Makuc
- Subjects
Flavonols ,Physalis ,Flavonoid ,Silica Gel ,Ether ,01 natural sciences ,Biochemistry ,High-performance liquid chromatography ,Analytical Chemistry ,chemistry.chemical_compound ,Organic chemistry ,Furans ,Chromatography, High Pressure Liquid ,chemistry.chemical_classification ,Flavonoids ,Wax ,Chromatography ,010405 organic chemistry ,010401 analytical chemistry ,Organic Chemistry ,General Medicine ,Thin-layer chromatography ,0104 chemical sciences ,chemistry ,visual_art ,Waxes ,visual_art.visual_art_medium ,Myricetin ,Quercetin ,Chromatography, Thin Layer - Abstract
Since Chinese lantern (Physalis alkekengi L.) represents a rich source of various bioactive secondary metabolites, there is an urge for its detailed characterization. Non-polar flavonoid aglycones represent one of the few bioactive species found in plant's cuticular waxes. The separation of flavonoids is already extensively covered in the literature, but methods dedicated to separation and identification of methylated flavonoids are rather scarce. In the present study a non-targeted approach for the separation, isolation and identification of methylated flavonoids present in P. alkekengi L. var. franchetii cuticular waxes was established. A rapid and simple separation on HPTLC silica gel was developed for preliminary screening of flavonoids. Fast HPLC-UV-MS(n) and HPLC-UV methods using a C6-Phenyl and a C18 stationary phase were also developed, respectively. In both cases, the right combination of temperature and tetrahydrofuran, as a mobile phase modifier, were shown to be crucial for a baseline separation of all studied compounds. By employing a semi-preparative analog of the C18 column, a simultaneous isolation of pure unknown analytes was achieved. Using these developed methods in combination with NMR, four 3-O-methylated flavonols were detected and identified in P. alkekengi L. var. franchetii cuticular waxes: myricetin 3,7,3'-trimethyl ether, quercetin 3,7-dimethyl ether, myricetin 3,7,3',5'-tetramethyl ether and quercetin 3,7,3'-trimethyl ether. Moreover, the simple and fast isocratic HPLC-UV-MS(n) method (under 8min) should prove useful in quality control of P. alkekengi L. var. franchetii by enabling chromatographic fingerprinting of external methylated flavonols. Finally, a rationale for the mechanism of separation of these metabolites by HPLC is also given, which establishes a foundation for future development of chromatographic methods for methylated flavonols and related compounds.
- Published
- 2015
24. NMR studies of anion-induced conformational changes in diindolylureas and diindolylthioureas
- Author
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Janez Plavec, Mark E. Light, Jennifer R. Hiscock, Philip A. Gale, and Damjan Makuc
- Subjects
anion recognition ,010402 general chemistry ,01 natural sciences ,Full Research Paper ,lcsh:QD241-441 ,NMR spectroscopy ,lcsh:Organic chemistry ,Ab initio quantum chemistry methods ,conformation analysis ,QD ,lcsh:Science ,Anion binding ,Conformational isomerism ,Indole test ,010405 organic chemistry ,Hydrogen bond ,Chemistry ,Chemical shift ,host–guest systems ,Organic Chemistry ,Nuclear magnetic resonance spectroscopy ,0104 chemical sciences ,Crystallography ,Heteronuclear molecule ,lcsh:Q - Abstract
The conformational properties of 1,3-diindolylureas and thioureas were studied by a combination of heteronuclear NMR spectroscopy and quantum mechanics calculations. NOE experiments showed that the anti–anti conformer along the C7–N7α bonds was predominant in DMSO-d6 solution in the absence of anions. Anion-induced changes in the 1H and 15N chemical shifts confirm the weak binding of chloride anions with negligible conformational changes. Strong deshielding of ureido protons and moderate deshielding of indole NH was observed upon the addition of acetate, benzoate, bicarbonate and dihydrogen phosphate, which indicated that the predominant hydrogen bond interactions occurred at the urea donor groups. Binding of oxo-anions caused conformational changes along the C7–N7α bonds and the syn–syn conformer was preferred for anion–receptor complexes. The conformational changes upon anion binding are in good agreement with energetic preferences established by ab initio calculations.
- Published
- 2011
25. Synthesis, structural and conformational studies of Z- and E-isomers of fluorinated C-6 isobutenyl N-methyl thymine derivatives
- Author
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Mario Cetina, Silvana Raić-Malić, Janez Plavec, Andrijana Meščić, Svjetlana Krištafor, Silvija Korunda, and Damjan Makuc
- Subjects
Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Pyrimidine ,Stereochemistry ,Organic Chemistry ,Environmental Chemistry ,Crystal structure ,mono- and difluorinated N-methyl thymine derivatives ,C-6 unsaturated side-chain ,Z- and E-isomers ,NMR conformational analysis ,positron emission tomography (PET) ,Physical and Theoretical Chemistry ,Pet tracer ,Biochemistry ,Thymine - Abstract
A new series of conformationally restricted pyrimidine derivatives bearing C-6 isobutenyl side-chain (2–9) has been prepared. The novel fluoroalkenyl pyrimidine nucleoside mimetic 3 as model compound for development of tracer molecule in positron emission tomography (PET) was synthesized by fluorination reaction of methoxytritylated pyrimidine derivative using diethylaminosulfur trifluoride (DAST). Conversion of one hydroxyl group to methoxytritylated, fluorinated, mesylated and acetylated pyrimidine derivatives (2, 3, 5–7 and 9) afforded a mixture of Z- and E-isomers in which Z-isomers were predominant. Conformational study of 1, and its fluorinated structural congeners 3 and 4 by the use of NOE experiments revealed predominant conformation of compounds where vinyl H-10 proton is spatially close to N-1 methyl and H-30b methylene protons and on the other hand H-30a methylene protons are close to C-5 methyl protons. The stereostructure of 1, 3-dihydroxyisobutenyl N- methyl thymine 1 was unambiguously confirmed by X- ray crystal structure analysis.
- Published
- 2011
26. Methoxymethyl (MOM) Group Nitrogen Protection of Pyrimidines Bearing C-6 Acyclic Side-Chains
- Author
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Tatjana Gazivoda Kraljević, Janez Plavec, Martina Petrovic, Tobias L. Ross, Damjan Makuc, Svjetlana Krištafor, Silvana Raić-Malić, and Simon M. Ametamey
- Subjects
Pyrimidine ,Nitrogen ,N-methoxymethyl protecting group ,Stereochemistry ,Pharmaceutical Science ,010402 general chemistry ,01 natural sciences ,Article ,C-6 isobutyl pyrimidine derivatives ,N-1 and N-3 regioisomers ,NOE experiments ,positron emission tomography (PET) ,Analytical Chemistry ,lcsh:QD241-441 ,chemistry.chemical_compound ,lcsh:Organic chemistry ,Drug Discovery ,Side chain ,Molecule ,Moiety ,Hydroxymethyl ,Physical and Theoretical Chemistry ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,Uracil ,Carbon ,0104 chemical sciences ,3. Good health ,Pyrimidines ,Chemistry (miscellaneous) ,Reagent ,Molecular Medicine ,Positron emission tomography (PET) ,Nucleoside - Abstract
Novel N-methoxymethylated (MOM) pyrimidine (4-13) and pyrimidine-2,4-diones (15-17) nucleoside mimetics in which an isobutyl side-chain is attached at the C-6 position of the pyrimidine moiety were synthesized. Synthetic methods via O-persilylated or N-anionic uracil derivatives have been evaluated for the synthesis of N-1- and/or N-3-MOM pyrimidine derivatives with C-6 acyclic side-chains. A synthetic approach using an activated N-anionic pyrimidine derivative afforded the desired N,N-1,3-diMOM and N-1-MOM pyrimidines 4 and 5 in good yield. Introduction of fluorine into the side-chain was performed with DAST as the fluorinating reagent to give a N,N-1,3-diMOM pyrimidine 13 with a 1-fluoro-3-hydroxyisobutyl moiety at C-6. Conformational study of the monotritylated N-1-MOM pyrimidine 12 by the use of the NOE experiments revealed the predominant conformation of the compound to be one where the hydroxymethyl group in the C-6 side-chain is close to the N-1-MOM moiety, while the OMTr is in proximity to the CH3-5 group. Contrary to this no NOE enhancements between the N-1-MOM group and hydroxymethyl or fluoromethyl protons in 13 were observed, which suggested a nonrestricted rotation along the C-6 side-chain. Fluorinated N,N-1,3-diMOM pyrimidine 13 emerged as a model compound for development of tracer molecules for non-invasive imaging of gene expression using positron emission tomography (PET). ISSN:1420-3049
- Published
- 2011
27. Potentiometric and 31P NMR studies on inositol phosphates and their interaction with iron(III) ions
- Author
-
Jana Kolar, Janez Plavec, Boris Pihlar, Martin Šala, and Damjan Makuc
- Subjects
Chemistry ,Ligand ,Organic Chemistry ,Inorganic chemistry ,Potentiometric titration ,General Medicine ,Nuclear magnetic resonance spectroscopy ,Phosphate ,Biochemistry ,Analytical Chemistry ,chemistry.chemical_compound ,Deprotonation ,Hydroxide ,Molecule ,Titration - Abstract
Potentiometric, conductometric and ³¹P NMR titrations have been applied to study interactions between myo-inositol hexakisphosphate (phytic acid), (±)-myo-inositol 1,2,3,5-tetrakisphosphate and (±)-myo-inositol 1,2,3-trisphosphate with iron(III) ions. Potentiometric and conductometric titrations of myo-inositol phosphates show that addition of iron increases acidity and consumption of hydroxide titrant. By increasing the Fe(III)/InsP(6) ratio (from 0.5 to 4) 3 mol of protons are released per 2 mol of iron(III). At first, phytates coordinate iron octahedrally between P2 and P1,3. The second coordination site represents P5 and neighbouring P4,6 phosphate groups. Complexation is accompanied with the deprotonation of P1,3 and P4,6 phosphate oxygens. At higher concentration of iron(III) intermolecular P-O-Fe-O-P bonds trigger formation of a polymeric network and precipitation of the amorphous Fe(III)-InsP(6) aggregates. (31)P NMR titration data complement the above results and display the largest chemical shift changes at pD values between 5 and 10 in agreement with strong interactions between iron and myo-inositol phosphates. The differences in T(1) relaxation times of phosphorous atoms have shown that phosphate groups at positions 1, 2 and 3 are complexated with iron(III). The interactions between iron(III) ions and inositol phosphates depend significantly on the metal to ligand ratio and an attempt to coordinate more than two irons per InsP(6) molecule results in an unstable heterogeneous system.
- Published
- 2011
28. Conformational changes of functionalised indole receptors upon their interaction with anions
- Author
-
Janez Plavec, Markus Albrecht, and Damjan Makuc
- Subjects
Indole test ,chemistry.chemical_compound ,Crystallography ,chemistry ,Heteronuclear molecule ,Bromide ,Hydrogen bond ,Ab initio quantum chemistry methods ,Stereochemistry ,Ab initio ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,Anion binding - Abstract
The conformational analysis of four C2-amido and C7-ureido functionalised indole anion receptors was performed by a combination of heteronuclear NMR spectroscopy and ab initio quantum mechanical calculations. NOE experiments showed that anti–anti conformation across C2–C2α and C7–N7α bonds is predominant in acetone solution in the absence of anions. Upon anion binding to receptors, syn–syn conformation becomes predominant. The conformational changes upon anion binding are in good agreement with energetic preferences established by ab initio calculations. Chemical shift changes induced by interaction of anions suggest that binding of chloride and bromide anions occurs primarily to H1 and H7α protons. Nitrate anions favour interaction with H7α and H7γ ureido protons, whereas acetate anions interact strongly with all four available hydrogen bond donor groups.
- Published
- 2010
29. The Halide Binding Behavior of 2-Carbamoyl-7-ureido-1H-indoles: Conformational Aspects
- Author
-
Christoph A. Schalley, Arto Valkonen, Janez Plavec, Kari Rissanen, Triyanti, Damjan Makuc, and Markus Albrecht
- Subjects
Indole test ,Conformational change ,Hydrogen bond ,medicine.drug_class ,Stereochemistry ,Organic Chemistry ,Quinoline ,Substituent ,Halide ,Carboxamide ,Nuclear magnetic resonance spectroscopy ,chemistry.chemical_compound ,chemistry ,medicine ,Physical and Theoretical Chemistry - Abstract
Indole-based anion receptors with an carboxamide unit in 2- and an urea in 7-position were prepared and found to bind halides (as well as acetate and nitrate) in chloroform solutions at room temperature. Investigations of the binding behaviour show that the receptor is selective for chloride. Surprisingly, the truncated receptor 3 without the 2-carbamoyl substituent shows the highest affinity for Cl–. Thorough 1H, 13C and 15N NMR investigations indicate different binding modes for acetate, nitrate and halides to the receptor 2. The observation of a major conformational change of this receptor during the binding of the halide ions leads to an understanding of the relative binding affinities of 3 > 4 > 2 for chloride. The results of the NMR study are supported by ab initio calculations. In addition, ESI FTICR MS competition experiments of the indole 2 and the quinoline 1 reveal the “self-aggregation” of the receptors and show that halides have a higher affinity to 2 than to 1.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
- Published
- 2009
30. Synthesis, structural studies, and cytostatic evaluation of 5,6-di-O-modified l-ascorbic acid derivatives
- Author
-
Janez Plavec, Draginja Mrvoš-Sermek, Tatjana Gazivoda, Marijeta Kralj, Lidija Šuman, Karlo Wittine, Mladen Mintas, Iva Lovrić, Silvana Raić-Malić, Mario Cetina, Krešimir Pavelić, and Damjan Makuc
- Subjects
Models, Molecular ,Magnetic Resonance Spectroscopy ,Double bond ,Stereochemistry ,Molecular Conformation ,Antineoplastic Agents ,Ascorbic Acid ,Crystallography, X-Ray ,Biochemistry ,Analytical Chemistry ,chemistry.chemical_compound ,Nucleophile ,Cell Line, Tumor ,Carbohydrate Conformation ,Humans ,Molecule ,chemistry.chemical_classification ,Molecular Structure ,Hydrogen bond ,Organic Chemistry ,General Medicine ,Ascorbic acid ,L-ascorbic acid ,configurational analysis ,conformational analysis ,single crystal X-ray diffraction ,cytostatic activity ,chemistry ,Heteronuclear molecule ,Dioxolane ,Drug Screening Assays, Antitumor ,Lactone - Abstract
The 5,6-di- O -tosylated derivative of l -ascorbic acid was synthesized by selective protection and deprotection of 2,3- and 5,6-dihydroxy functional groups involving 5,6-ditosylation in the final step, while the novel 6-acetoxy, 6-hydroxy, and 6-chloro derivatives of 4,5-didehydro- l -ascorbic acid were obtained by reaction of ditosylated compound with nucleophilic reagents. The analysis of 3 J H-4–H-5 homonuclear coupling constants shows that all l -ascorbic acid derivatives except for epoxy and 4,5-didehydro compounds exist in high population as gauche conformers across C-4–C-5 bonds, while 3 J C-3–H-5 heteronuclear coupling constants in 4,5-didehydro derivatives indicate cis geometry along C-4–C-5 double bond. The X-ray crystal structure analysis of 2,3-di- O -benzyl-5,6-epoxy- and 5,6-isopropylidene- l -ascorbic acid shows that the oxygen atoms attached at positions 2 and 3 of the lactone ring are disposed in a synperiplanar fashion. Besides that, the dioxolane ring adopts half-chair conformation. The molecules of epoxy derivative are joined into infinite chains by one weak hydrogen bond of C–H⋯O type. Two O–H⋯O, and C–H⋯O hydrogen bonds link the molecules of 5,6-di- O -isopropylidene compound into two-dimensional network. 6-Chloro derivative of 2,3-di- O -benzyl- l -ascorbic acid showed the best cytostatic effects against all tested malignant tumor cells (IC 50 : ∼18 μM).
- Published
- 2006
31. Potentiometric and ³¹P NMR studies on inositol phosphates and their interaction with iron(III) ions
- Author
-
Martin, Sala, Damjan, Makuc, Jana, Kolar, Janez, Plavec, and Boris, Pihlar
- Subjects
Ions ,Structure-Activity Relationship ,Magnetic Resonance Spectroscopy ,Phytic Acid ,Inositol Phosphates ,Iron ,Potentiometry ,Hydrogen-Ion Concentration ,Protons ,Ligands - Abstract
Potentiometric, conductometric and ³¹P NMR titrations have been applied to study interactions between myo-inositol hexakisphosphate (phytic acid), (±)-myo-inositol 1,2,3,5-tetrakisphosphate and (±)-myo-inositol 1,2,3-trisphosphate with iron(III) ions. Potentiometric and conductometric titrations of myo-inositol phosphates show that addition of iron increases acidity and consumption of hydroxide titrant. By increasing the Fe(III)/InsP(6) ratio (from 0.5 to 4) 3 mol of protons are released per 2 mol of iron(III). At first, phytates coordinate iron octahedrally between P2 and P1,3. The second coordination site represents P5 and neighbouring P4,6 phosphate groups. Complexation is accompanied with the deprotonation of P1,3 and P4,6 phosphate oxygens. At higher concentration of iron(III) intermolecular P-O-Fe-O-P bonds trigger formation of a polymeric network and precipitation of the amorphous Fe(III)-InsP(6) aggregates. (31)P NMR titration data complement the above results and display the largest chemical shift changes at pD values between 5 and 10 in agreement with strong interactions between iron and myo-inositol phosphates. The differences in T(1) relaxation times of phosphorous atoms have shown that phosphate groups at positions 1, 2 and 3 are complexated with iron(III). The interactions between iron(III) ions and inositol phosphates depend significantly on the metal to ligand ratio and an attempt to coordinate more than two irons per InsP(6) molecule results in an unstable heterogeneous system.
- Published
- 2010
32. Anion-induced conformational changes in 2,7-disubstituted indole-based receptors
- Author
-
Damjan Makuc, Janez Plavec, Martina Lenarčič, Philip A. Gale, and Gareth W. Bates
- Subjects
Indole test ,Hydrogen bond ,Organic Chemistry ,Nuclear magnetic resonance spectroscopy ,Biochemistry ,Medicinal chemistry ,Chloride ,chemistry.chemical_compound ,chemistry ,Thiourea ,Bromide ,Amide ,Urea ,medicine ,Organic chemistry ,Physical and Theoretical Chemistry ,medicine.drug - Abstract
The conformational preorganization and anion-induced conformational changes of indole-based receptors functionalized with an amide group at the 2-position and a variety of amide, urea and thiourea moieties at the 7-position have been studied by the means of NMR spectroscopy. NOE experiments showed that anti-anti orientation across C2-C2alpha and C7-N7alpha bonds is preferred for receptors 1-4 in acetone solution in the absence of anions. Anion-receptor interactions have been evaluated through (1)H and (15)N chemical shift changes. In 2,7-bis-carboxamido functionalized indoles the interaction with chloride and bromide anions primarily occurs at the indole H1 proton. The introduction of urea and thiourea moieties increases the number of hydrogen bond donor sites which manifests itself in a distribution of halide-receptor interactions among the H1, H7alpha and H7gamma protons. Acetate anions also interact strongly with indole and urea NH donor groups, whereas nitrate anions interact solely with H7alpha and H7gamma urea/thiourea protons. NOE enhancements in the presence of anions revealed that anion-receptor complexes favour the syn-syn conformation of the C2 and C7 substituents.
- Published
- 2009
33. Synthetic transporters for sulfate: a new method for the direct detection of lipid bilayer sulfate transport
- Author
-
Nathalie Busschaert, Damjan Makuc, Cally J. E. Haynes, Neil J. Wells, Janez Plavec, Philip A. Gale, Katrina A. Jolliffe, Louise E. Karagiannidis, Marco Wenzel, and Philip G. Young
- Subjects
inorganic chemicals ,Tris ,Inorganic chemistry ,Supramolecular chemistry ,General Chemistry ,Membrane transport ,Chloride ,Combinatorial chemistry ,Sulfate transport ,chemistry.chemical_compound ,Membrane ,chemistry ,medicine ,Sulfate ,Lipid bilayer ,medicine.drug - Abstract
The transmembrane transport of anions by small synthetic molecules is a growing field in supramolecular chemistry and has focussed mainly on the transmembrane transport of chloride. On the other hand, the transport of the highly hydrophilic sulfate anion across lipid bilayers is much less developed, even though the inability to transport sulfate across cellular membranes has been linked to a variety of genetic diseases. Tris-thioureas possess high sulfate affinities and have been shown to be excellent chloride and bicarbonate transporters. Herein we report the sulfate transport abilities of a series of tris-ureas and tris-thioureas based on a tris(2-aminoethyl)amine or cyclopeptide scaffold. We have developed a new technique based on 33S NMR that can be used to monitor sulfate transport, using 33S-labelled sulfate and paramagnetic agents such as Mn2+ and Fe3+ to discriminate between intra- and extravesicular sulfate. Reasonable sulfate transport abilities were found for the reported tris-ureas and tris-thioureas, providing a starting point for the development of more powerful synthetic sulfate transporters that can be used in the treatment of certain channelopathies or as a model for biological sulfate transporters.
- Published
- 2014
34. Antiviral and cytostatic evaluation of the novel 6-acyclic chain substituted thymine derivatives
- Author
-
Svjetlana Prekupec, Robert Snoeck, Sandra Kraljević, Silvana Raić-Malić, Graciela Andrei, Marijeta Kralj, Jan Balzarini, Janez Plavec, Mladen Mintas, Damjan Makuc, Krešimir Pavelić, and Erik De Clercq
- Subjects
0301 basic medicine ,Magnetic Resonance Spectroscopy ,Pyrimidine ,Chemistry ,Stereochemistry ,030106 microbiology ,Antineoplastic Agents ,Microbial Sensitivity Tests ,General Medicine ,Nuclear magnetic resonance spectroscopy ,C-6 fluoroalkylated pyrimidine derivatives ,conformational analysis ,antiviral activity ,cytostatic activity ,apoptosis ,Antiviral Agents ,01 natural sciences ,Mass Spectrometry ,0104 chemical sciences ,Thymine ,010404 medicinal & biomolecular chemistry ,03 medical and health sciences ,chemistry.chemical_compound ,Chain (algebraic topology) ,Cell Line, Tumor ,Side chain ,Humans ,Drug Screening Assays, Antitumor - Abstract
A series of the novel 5-methyl pyrimidine derivatives with an acyclic side chain at the C-6 position were synthesized using lithiation of a 2,4-dimethoxy-5,6-dimethyl pyrimidine and subsequent nucleophilic addition or substitution reactions of the organolithium intermediate thus obtained with acetaldehyde, epichlorhydrine, fluorinated ketones and fluorinated ester. The novel compounds were evaluated for their cytostatic and antiviral activities. Among all the compounds evaluated, two fluorinated acyclic pyrimidine derivatives showed the highest cytostatic activities. The compound containing a 2-hydroxy-3,3,3-trifluoro-1-propenyl side chain exhibited a pronounced effect against breast carcinoma (MCF-7, IC50=8.38 μg/ml), while the compound with a 2-fluoromethyl-2-acetoxypropyl chain exhibited moderate effect against cervical carcinoma (HeLa, IC50=19.73 μg/ml).
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