Péter Horváth

Semmelweis University, Budapeŝto, Budapest, Hungary

Are you Péter Horváth?

Claim your profile

Publications (57)97.04 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: B3LYP is one of the most widely used functional for the prediction of electronic circular dichroism spectra, however if the studied molecule contains aromatic nitro group computations may fail to produce reliable results. A test set of molecules of known stereochemistry were synthesized to study this phenomenon in detail. Spectra were computed by B3LYP and CAM-B3LYP functionals with 6-311++G(2d,2p) basis set. It was found that the range separated CAM-B3LYP gives better predictions than B3LYP for all test molecules. Fragment population analysis revealed that the nitro groups form highly localized molecule orbitals but the exact composition depends on the functional. CAM-B3LYP allows sufficient spatial overlap between the nitro group and distant parts of the molecule, which is necessary for the accurate description of excited states especially for charge transfer states. This phenomenon and the synthesized test molecules can be used to benchmark theoretical methods as well as to help the development of new functionals intended for spectroscopical studies.
    Full-text · Article · Nov 2015 · Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy
  • [Show abstract] [Hide abstract]
    ABSTRACT: In Cirsium eriophorum fruit, the main neolignan and sesquineolignan compounds, denominated prebalanophonin (preBA) and prepicrasmalignan (prePI), were determined for the first time in the plant kingdom using a combination of optimized acid treatments and complementary spectroscopic (HPLC-MS, GC-MS, CD and NMR) methods. Analysis of fruit parts separated via germination, demonstrated the specific accumulation of these compounds, since preBA and prePI were exclusively found in the fruit wall. Based on quantitative approaches obtained by HPLC-UV measurements, the fruit wall was found to contain extraordinarily high amounts of preBA (4.57%) and prePI (2.88%) allowing their high-yield isolation by preparative HPLC. Optimized acidic treatment (2 N trifluoroacetic acid, 50 °C, 15 min) of the wall extract resulted in the quantitative transformation of preBA and prePI into balanophonin (BA) and picrasmalignan (PI), as a result of acid-catalyzed cyclization by the SN2 reaction. Consequently, acid-treated wall extract was found to be the richest raw material containing BA and PI (5.3% and 3.10%), reported to date
    No preview · Article · Feb 2015 · PROCESS BIOCHEMISTRY
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of the study was to characterise the unique chromatographic properties of tetrahydrofuran (THF) based on hydrogen-bonding interactions with weakly acidic compounds (pK a = 7.4–12.48) including steroids with phenolic hydroxyl groups, their substituted derivatives and heterocyclic amides having different polar functional groups (log P = 1.15–4.78). The results suggested that the organic modifier does not simply affect retention by changing the hydrophobicity of eluent, but rather specifically modifies the nature of the analyte–stationary phase interaction. In the water/isopropanol (IPA)/THF eluent mixture THF forms a hydrogen-bonded complex with the phenolic steroid compounds. The apparent formation of the THF–analyte complex depended on the proportion of components in the ternary mobile phase employed (from 70:30:0 to 70:0:30 v/v/v). The weakly acidic model compounds showed an increasing retention time with increasing THF concentration. This effect of THF was found to be a solvent-specific interaction, which was only observed in the presence of IPA. The systematic modification of the phase ratio of organic modifiers exerts a great influence on retention time and changes the separation processes over a wide range. In the case of other protic solvents (methanol, ethanol) we could not observe this selective chromatographic behaviour. From the point of view of chromatographic practice, the use of THF–IPA co-modifiers may increase the selectivity and provide excellent possibilities for separation of weakly acidic compounds including the large family of phenolic compounds.
    No preview · Article · May 2013 · Chromatographia
  • [Show abstract] [Hide abstract]
    ABSTRACT: Six 3-O- and 6-O-glucosides of morphine and codeine derivatives were synthesized by means of glucosylation with acetobromo-α-d-glucose. O-Glucosylation at C6 was carried out by the Koenigs-Knorr method, whereas the 3-O-glycoside of morphine was synthesized directly upon stirring morphine with acetobromo-α-d-glucose and aqueous sodium hydroxide in acetone. Complete 1H and 13C NMR assignments are presented for each synthesized compound based on one- and two-dimensional homo- and heteronuclear NMR techniques. Circular dichroism, ultraviolet absorbance, and high-resolution mass spectroscopy data ensure identification and structural characterization of the O-glucoside conjugates. The synthesized glucoside conjugates are potential analgesics; the presented spectral and chromatographic data are useful references for various analytical and metabolic studies including samples of biological origin. Graphical Abstract
    No preview · Article · Feb 2013 · Monatshefte für Chemie
  • [Show abstract] [Hide abstract]
    ABSTRACT: NMDA receptors form a major subdivision of the ionotropic glutamate receptor family that mediates excitatory synaptic transmission in the brain. Series of 1-substituted 1,2-dihydroimidazo[5,1-b]quinazolinediones were synthesized and found to have potent nanomolar activity at the glycine site of the NMDA receptor. Imidazoquinazolinediones were prepared by cyclocondensation of 4-oxo-quinazoline-2-carboxamide with aldehydes and orthoesters with good yields. The formed enantiomers were separated by chiral HPLC. The absolute configuration of pure enantiomers is elucidated by combined CD/Quantumchemical time-dependent DFT calculation method (TDDFT).
    No preview · Article · Dec 2012 · Tetrahedron
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The enantiomer-specific characterization of ofloxacin–cyclodextrin complexes was carried out by a set of complementary analytical techniques. The apparent stability constants of the ofloxacin enantiomers with 20 different cyclodextrins at two different pH values were determined to achieve good resolution capillary electrophoresis enantioseparation either to establish enantioselective drug analysis assay, or to interpret and design improved host–guest interactions at the molecular level. The cyclodextrins studied differed in the nature of substituents, degree of substitution (DS), charge and purity, allowing a systematic test of these properties on the complexation. The seven-membered beta-cyclodextrin and its derivatives were found to be the most suitable hosts. Highest stability and best enantioseparation were observed for the carboxymethylated-beta-cyclodextrin (DS ~ 3.5). The effect of substitution pattern (SP) was investigated by molecular modeling, verifying that SP greatly affects the complex stability. Induced circular dichroism was observed and found especially significant on carboxymethylatedbeta-cyclodextrin. The complex stoichiometry and the geometry of the inclusion complexes were determined by 1H NMR spectroscopy, including 2D ROESY techniques. Irrespective of the kind of cyclodextrin, the complexation ratio was found to be 1:1. The alfa-cyclodextrin cavity can accommodate the oxazine ring only, whereas the whole tricyclic moiety can enter the beta- and gamma-cyclodextrin cavities. These equilibrium and structural information offer molecular basis for improved drug formulation.
    Full-text · Article · Aug 2012 · Journal of inclusion phenomena and macrocyclic chemistry
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to investigate the impact of fluoroquinolone resistance on the existence and dynamic of MRSA clones. Resistance to ciprofloxacin was induced in strains of community-acquired (CA) MRSA from various sequence types and the fitness cost suffered by mutant derivatives measured in a propagation assay. In addition, the fitness of fluoroquinolone resistant health care-associated (HA) MRSA isolates from major clones prevalent in Hungary were compared with each other and with those of the CA-MRSA derivatives. The genetic background of fluoroquinolone resistance and fitness cost in CA-MRSA was investigated. The fitness cost observed in the CA-MRSA derivatives proved diverse; the derivatives of the ST30-MRSA-IV strain suffered significantly greater fitness cost than those of the ST8-MRSA-IV and ST80-MRSA-IV isolates. Strains from the New York-Japan (ST5-MRSA-II), South German (ST228-MRSA-I) and EMRSA-15 (ST22-MRSA-IV) HA-MRSA clones proved more viable than CA-MRSA derivatives with similar MIC values to ciprofloxacin and HA-MRSA strains from the Hungarian/Brazilian clone (ST239-MRSA-III). Our strains from the New York-Japan, South-German and EMRSA-15 clones seem to have a competitive edge over the tested CA-MRSA isolates in the health care setting. The greater fitness observed in our New York-Japan and South-German strains could account for the replacement by them of the Hungarian/Brazilian clone in Hungary about ten years ago. Alterations in relevant genes were detected. The Ser80 → Phe mutation in the grlA gene may have seriously compromised viability. Surprisingly silent nucleotide substitutions in the grlB gene seemed to impact fitness in derivatives of the ST30-MRSA-IV isolate.
    No preview · Article · Jan 2012 · European Journal of Clinical Microbiology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: NMDA receptors form a major subdivision of the ionotropic glutamate receptor family that mediates excitatory synaptic transmission in the brain. Series of 1-substituted 1,2-dihydroimidazo[5,1-b]quinazolinediones were synthesized and found to have potent nanomolar activity at the glycine site of the NMDA receptor. Imidazoquinazolinediones were prepared by cyclocondensation of 4-oxo-quinazoline-2-carboxamide with aldehydes and orthoesters with good yields. The formed enantiomers were separated by chiral HPLC. The absolute configuration of pure enantiomers is elucidated by combined CD/Quantumchemical time-dependent DFT calculation method (TDDFT).
    Full-text · Article · Jan 2012
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ceramide-like penetration enhancers have been synthesized by isosteric replacements of the 1-hydroxymethyl and amide moieties of natural ceramides. Metabolically more stable oxime and five-membered heterocyclic (1,2,4-oxadiazole, 1,2,4-triazole, tetrazole) analogues are more polar and possess H-bond acceptor properties, which make them potentially useful in optimizing key intermolecular features in interactions between the modified ceramide structures and the lipid layers of stratum corneum.
    Full-text · Article · Feb 2011 · Tetrahedron Letters
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Three new natural ecdysteroids viz. 22-dehydro-20-deoxy-ajugasterone C (1), 1-hydroxy-22-deoxy-20,21-didehydro-ecdysone (2) and 22-deoxy-20,21-didehydro-ecdysone (3) were isolated from the methanol extract of the roots of Serratula wolffii. The structures of compounds 1-3 were established by various spectroscopic techniques, including one- and two-dimensional NMR, circular dichroism and mass spectroscopic methods.
    Full-text · Article · May 2010 · Magnetic Resonance in Chemistry
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In the authors' earlier study the relative aerobic power of Hungarian top-level male water polo players was found to be smaller than that of other top-level athletes, while their echocardiographic parameters proved to be the most characteristic of the athlete's heart. In the present investigation echocardiographic and spiroergometric data of female top-level water polo players were compared to those of other female elite athletes and of healthy, non-athletic subjects. Relative aerobic power in the water polo players was lower than in endurance athletes. Mean resting heart rates were the slowest in the water polo players and endurance athletes. Morphologic indicators of the heart (body size related left ventricular wall thickness and muscle mass) were the highest in the water polo players, endurance and power athletes. In respect of diastolic functions (diastolic early and late peak transmitral flow velocities) no difference was seen between the respective groups.These results indicate that, similarly to the males, top-level water polo training is associated with the dimensional parameters of the heart rather than with relative aerobic power. For checking the physical condition of female water polo players spiroergometric tests seem to be less appropriate than swim-tests with heart rate recovery studies such as the ones used in the males.
    Full-text · Article · Dec 2009 · Acta Physiologica Hungarica
  • András Gergely · Péter Horváth · György Szász · Gábor Veress
    [Show abstract] [Hide abstract]
    ABSTRACT: A three-step gradient reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed for the separation of dehydroepiandrosterone (DHEA), its sulfate ester (DHEA-S), its three C7-oxidized metabolites (7αOH-DHEA, 7βOH-DHEA, 7-keto-DHEA), and its biosynthetic congeners (androstenedione, testosterone, estradiol, pregnenolone). This new method allows the quantitative characterization of DHEA metabolism and biosynthetic transformation under given physiological, pathological, or therapeutically influenced circumstances. Tetrahydrofuran probably acts as a proton acceptor coadsorbent, while isopropanol behaves as a proton donor during the separation of testosterone, estradiol, and the stereoisomers of 7-OH-DHEA. Figure Optimized gradient RP-HPLC results in full separation of DHEA from its biosynthetic congeners and metabolites
    No preview · Article · Sep 2009 · Analytical and Bioanalytical Chemistry
  • M Füzi · P Horváth
    [Show abstract] [Hide abstract]
    ABSTRACT: Until recently the etiology of bovine spongiform encephalopathy (BSE) was considered uniform. The infectious agent was thought to be a single strain of prion (posttranslationally altered form of normal prion protein: PrPSc) retaining its biochemical and biological characteristics during interspecies transmission. However, alternate PrPSc signatures through large-scale screening have recently been detected. In addition, genetic alterations governing susceptibility to prion infection and a mutation (E211K) capable of eliciting spontaneous BSE have been demonstrated. Thus, the spectrum of BSEs have broadened and three PrPSc variants (BSE-C, BSE-H and BSE-L) are now defined. Moreover, a new condition resembling BSE, idiopathic brainstem neuronal chromatolysis (IBNC), has been described that may also turn out to be a prion disease. Since one of the new BSE variants, L-type BSE, proved highly pathogenic detection and further characterization of the new conditions are essential.
    No preview · Article · Apr 2009 · Acta Microbiologica et Immunologica Hungarica
  • [Show abstract] [Hide abstract]
    ABSTRACT: Isoflavones are suitable guest molecules for inclusion complex formation with cyclodextrins (CDs). The molecular encapsulation with CDs results in a solid, molecularly dispersed form and in a significantly improved aqueous solubility of isoflavones. Genistein, a key isoflavone constituent of Ononidis spinosae radix was found to form a supramolecular, non-covalent inclusion complex with both beta-cyclodextrin (beta-CD) and gamma-cyclodextrin (gamma-CD), while it did not form a stable complex with alpha-CD. The guest genistein was found to spatially located in the less polar cavity of cyclodextrin. The isolated binary genistein/CD complexes appeared novel crystalline lattices. The in vitro dissolution of genistein entrapped into both beta- and gamma-CD, significantly surpassed that of the plain isoflavone.
    No preview · Article · Jul 2008 · Journal of Pharmaceutical and Biomedical Analysis
  • Source

    Full-text · Article · Sep 2007 · European Journal of Pharmaceutical Sciences
  • [Show abstract] [Hide abstract]
    ABSTRACT: Enantioselective solubility of rac-norgestrel was found in the presence of γ-cyclodextrin or hydroxypropyl-γ-cyclodextrin. In both cases the efficacious enantiomer was dissolved in greater extent. Calculating the molar absorptivity and molar ellipticity spectra of the γ- and hydroxypropyl-γ-cyclodextrin aqueous complexes, a simple and rapid direct circular dichroism (CD) spectrometric method was obtained for the determination of the enantiomer ratio in aqueous solutions.
    No preview · Article · Mar 2007 · Journal of Inclusion Phenomena
  • [Show abstract] [Hide abstract]
    ABSTRACT: An attenuated neurogenic broncho-constriction underpinned by a decrease in sensory neuropeptide release has been shown to be characteristic of cisplatin-induced neuropathy. The present work was to explore if beyond neuropeptide release, cisplatin at a treatment schedule attaining sensory neuropathy, produced changes in the expression of the receptors of sensory neuropeptides such as somatostatin, calcitonin gene-related peptide (CGRP) and substance P (SP) in bronchial tissue of the rat. Twenty-four Wistar rats were divided into three groups. The animals in the "Treatment groups 1 and 2" were given cisplatin (1.5mgkg(-1)) and mannitol (75mgkg(-1)) over 5 days. The rats in the "Control" group were given mannitol+isotonic saline. Four animals from each group were used to study the expression pattern of the neuropeptide receptors in bronchial tissue. The levels of somatostatin receptor 4 (SSTR 4), neurokinin 1 (NK1), neurokinin 2 (NK2) and CGRP receptor expression were examined by quantitative real time polymerase chain reaction (RT-PCR) method, 11 and 22 days after the last cisplatin/vehicle dose. The cisplatin treatment significantly increased plasma somatostatin immunoreactivity and the expression of SSTR4 receptor detected both on the 11th and 22nd post-treatment days with no change in either CGRP, NK1, and NK2 receptor gene expression or plasma CGRP and substance P levels. We conclude that cisplatin neuropathy is accompanied by an increase in plasma somatostatin immunoreactivity with an increase in SSTR4 expression in rats.
    No preview · Article · Mar 2006 · Neuropeptides
  • [Show abstract] [Hide abstract]
    ABSTRACT: Dissolution of hydrophobic rac-norgestrel in aqueous gamma-cyclodextrin (gamma-CyD) and hydroxypropyl-gamma-cyclodextrin (HP-gamma-CyD) solutions was investigated, and enantioselective dissolution was observed. (-)-Norgestrel, the eutomer molecule, was dissolved to a greater extent using each of the CyDs, although the effect was more significant in the case of HP-gamma-CyD. A circular dichroism (CD) spectroscopic method based on measurement of the anisotropy factor was applied for the determination of the enantiomer ratio. The concentration and the enantiomer ratio of norgestrel were determined indirectly in octanol after extraction. Optical rotation dispersion (ORD) measurements could confirm that neither the free CyDs nor their inclusion complexes could get into the organic phase during transport to octanol. Only the norgestrel molecules were able to get into the organic phase, although the enantiomer ratio remained the same as was obtained in the aqueous CyD solution.
    No preview · Article · Jan 2006 · Chirality
  • [Show abstract] [Hide abstract]
    ABSTRACT: We studied if attenuated neurogenic bronchoconstriction was associated with a change in sensory neuropeptide release in preparations from rats with cisplatin-induced neuropathy. Electrical field stimulation (100 stimuli, 20 V, 0.1 ms, 20 Hz) induced an increase in the release of somatostatin, calcitonin gene-related peptide (CGRP) and substance P determined by radioimmunoassay from baseline 0.18+/-0.01, 0.17+/-0.01 and 0.86+/-0.02, to 0.59+/-0.02, 1.77+/-0.04 and 5.96 fmol/mg wet tissue weight, respectively, in organ fluid of tracheal tubes from rats. This was significantly attenuated to post-stimulation values of 0.36+/-0.02, 0.45+/-0.02, 4.68+/-0.24 fmol/mg wet tissue weight for somatostatin, CGRP, and substance P, respectively, with a significant decrease in field stimulation-induced contraction of bronchial preparations from animals 11 days after a 5-day treatment period with cisplatin (1.5 mg/kg i.p. once a day). The cisplatin-treated animals developed sensory neuropathy characterized by a 40% decrease in femoral nerve conduction velocity. The results show that a decrease in tracheo-bronchial sensory neuropeptide release associates with feeble bronchomotor responses in rats with cisplatin-induced sensory neuropathy.
    No preview · Article · Feb 2005 · European Journal of Pharmacology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We constructed and analyzed a new cell line called HT5-1, which stably expresses an enhanced green fluorescent protein-tagged version of the rat vanilloid receptor 1 (VR1/TRPV1). The fluorescent receptor allowed easy measurement of receptor expression and expression level-based purification of cells via fluorescence-activated cell sorting. The HT5-1 cell line was compared to cells transiently transfected with the fluorescent receptor, to cells expressing the native rat vanilloid receptor, and to isolated capsaicin-sensitive rat trigeminal sensory neurons. Fura-2 microfluorimetry measurements of the calcium influx upon capsaicin induction showed that, by contrast to transiently transfected cells, HT5-1 cells respond uniformly to the stimulation, due to the similar level of receptor expression in individual cells. HT5-1 cells showed similar behaviour to isolated trigeminal root ganglion neurons, including marked tachyphylaxis upon repeated capsaicin induction, and a lack of calcium ion release from intracellular storage sites.
    Preview · Article · Feb 2005 · Cellular & Molecular Biology Letters

Publication Stats

417 Citations
97.04 Total Impact Points

Institutions

  • 1999-2015
    • Semmelweis University
      • • Department of Pharmaceutical Chemistry
      • • Department of Medical Microbiology
      Budapeŝto, Budapest, Hungary
  • 2000-2007
    • University of Debrecen
      • • Department of Pharmaceutical Chemistry
      • • Department of Pharmacology and Pharmacotherapy
      • • Department of Pulmonology
      Debreczyn, Hajdú-Bihar, Hungary
  • 2006
    • Debreceni Egyetem, Orvos- és Egészségtudományi Centrum
      Debreczyn, Hajdú-Bihar, Hungary