György Dombi

University of Szeged, Szeged, Csongrad megye, Hungary

Are you György Dombi?

Claim your profile

Publications (137)94.39 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Suppositories are important tools for individual therapy, especially in paediatrics, and an instrumental assay method has become necessary for the quality control of dosage units. The aim of this work was to develop a rapid, effective high-performance liquid chromatography method to assay aminophenazone in extemporaneous suppositories prepared with two different suppository bases, adeps solidus and massa macrogoli. With a novel sample preparation method developed by the authors, 4-dimethylaminoantipyrine was determined in these suppository bases with 95-105% recovery. The measurements were carried out on a Shimadzu Prominence ultra high-performance liquid chromatography system equipped with a 20 μl sample loop. The separation was achieved on a Hypersil ODS column, with methanol, sodium acetate buffer (pH 5.5±0.05, 0.05 M, 60:40, v/v) as the mobile phase at a flow rate of 1.5 ml/min. The chromatograms were acquired at 253 nm. The chromatographic method was fully validated in accordance with current guidelines. The presented data demonstrate the successful development of a rapid, efficient and robust sample preparation and high-performance liquid chromatography method for the routine quality control of the dosage units of suppositories containing 4-dimethylaminoantipyrine.
    Indian Journal of Pharmaceutical Sciences 01/2014; 76(1):31-7. · 0.34 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Combined drug products have the advantages of better patient compliance and possible synergic effects. The simultaneous application of several active ingredients at a time is therefore frequently chosen. However, the quantitative analysis of such medicines can be challenging. The aim of this study is to provide a validated method for the investigation of a multidose packed oral powder that contained acetylsalicylic acid, paracetamol and papaverine-HCl. Reversed-phase high-pressure liquid chromatography was used. The Agilent Zorbax SB-C18 column was found to be the most suitable of the three different stationary phases tested for the separation of the components of this sample. The key parameters in the method development (apart from the nature of the column) were the pH of the aqueous phase (set to 3.4) and the ratio of the organic (acetonitrile) and the aqueous (25 mM phosphate buffer) phases, which was varied from 7:93 (v/v) to 25:75 (v/v) in a linear gradient, preceded by an initial hold. The method was validated: linearity, precision (repeatability and intermediate precision), accuracy, specificity and robustness were all tested, and the results met the ICH guidelines.
    Journal of chromatographic science 12/2013; · 0.79 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This review aims to create an overview of the currently available results of site-directed mutagenesis studies on transient receptor potential vanilloid type 1 (TRPV1) receptor. Systematization of the vast number of data on the functionally important amino acid mutations of TRPV1 may provide a clearer picture of this field, and may promote a better understanding of the relationship between the structure and function of TRPV1. The review summarizes information on 112 unique mutated sites along the TRPV1, exchanged to multiple different residues in many cases. These mutations influence the effect or binding of different agonists, antagonists, and channel blockers, alter the responsiveness to heat, acid, and voltage dependence, affect the channel pore characteristics, and influence the regulation of the receptor function by phosphorylation, glycosylation, calmodulin, PIP2, ATP, and lipid binding. The main goal of this paper is to publish the above mentioned data in a form that facilitates in silico molecular modelling of the receptor by promoting easier establishment of boundary conditions. The better understanding of the structure-function relationship of TRPV1 may promote discovery of new, promising, more effective and safe drugs for treatment of neurogenic inflammation and pain-related diseases and may offer new opportunities for therapeutic interventions.
    Molecular Pain 06/2013; 9(1):30. · 3.77 Impact Factor
  • Source
  • [Show abstract] [Hide abstract]
    ABSTRACT: Rectal drug delivery is currently at the focus of attention. Surfactants promote drug release from the suppository bases and enhance the formulation properties. The aim of our work was to develop a sample preparation method for HPLC analysis for a suppository base containing 95% hard fat, 2.5% Tween 20 and 2.5% Tween 60. A conventional sample preparation method did not provide successful results as the recovery of the drug failed to fulfil the validation criterion 95-105%. This was caused by the non-ionic surfactants in the suppository base incorporating some of the drug, preventing its release. As guidance for the formulation from an analytical aspect, we suggest a well defined surfactant content based on the turbidimetric determination of the CMC (critical micelle formation concentration) in the applied methanol-water solvent. Our CMC data correlate well with the results of previous studies. As regards the sample preparation procedure, a study was performed of the effects of ionic strength and pH on the drug recovery with the avoidance of degradation of the drug during the procedure. Aminophenazone and paracetamol were used as model drugs. The optimum conditions for drug release from the molten suppository base were found to be 100mM NaCl, 20-40mM NaOH and a 30min ultrasonic treatment of the final sample solution. As these conditions could cause the degradation of the drugs in the solution, this was followed by NMR spectroscopy, and the results indicated that degradation did not take place. The determined CMCs were 0.08mM for Tween 20, 0.06mM for Tween 60 and 0.04mM for a combined Tween 20, Tween 60 system.
    Journal of pharmaceutical and biomedical analysis 05/2013; 83C:149-156. · 2.45 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The availability of suppositories in Hungary, especially in clinical pharmacy practice, is usually provided by extemporaneous preparations. Due to the known advantages of rectal drug administration, its benefits are frequently utilized in pediatrics. However, errors during the extemporaneous manufacturing process can lead to non-homogenous drug distribution within the dosage units. To determine the root cause of these errors and provide corrective actions, we studied suppository samples prepared with exactly known errors using both cerimetric titration and HPLC technique. Our results show that the most frequent technological error occurs when the pharmacist fails to use the correct displacement factor in the calculations which could lead to a 4.6% increase/decrease in the assay in individual dosage units. The second most important source of error can occur when the molding excess is calculated solely for the suppository base. This can further dilute the final suppository drug concentration causing the assay to be as low as 80%. As a conclusion we emphasize that the application of predetermined displacement factors in calculations for the formulation of suppositories is highly important, which enables the pharmacist to produce a final product containing exactly the determined dose of an active substance despite the different densities of the components.
    Saudi Pharmaceutical Journal 01/2013; · 0.95 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Transient receptor potential vanilloid 1 (TRPV1) is a non-selective cation channel involved in pain sensation and in a wide range of non-pain-related physiological and pathological conditions. The aim of the present study was to explore the effects of selected heavy metal cations on the function of TRPV1. The cations ranked in the following sequence of pore-blocking activity: Co(2+) [half-maximal inhibitory concentration (IC(50)) = 13 μM] > Cd(2+) (IC(50) = 38 μM) > Ni(2+) (IC(50) = 62 μM) > Cu(2+) (IC(50) = 200 μM). Zn(2+) proved to be a weak (IC(50) = 27 μM) and only partial inhibitor of the channel function, whereas Mg(2+), Mn(2+) and La(3+) did not exhibit any substantial effect. Co(2+), the most potent channel blocker, was able not only to compete with Ca(2+) but also to pass with it through the open channel of TRPV1. In response to heat activation or vanilloid treatment, Co(2+) accumulation was verified in TRPV1-transfected cell lines and in the TRPV1+ dorsal root ganglion neurons. The inhibitory effect was also demonstrated in vivo. Co(2+) applied together with vanilloid agonists attenuated the nocifensive eye wipe response in mice. Different rat TRPV1 pore point mutants (Y627W, N628W, D646N and E651W) were created that can validate the binding site of previously used channel blockers in agonist-evoked (45)Ca(2+) influx assays in cells expressing TRPV1. The IC(50) of Co(2+) on these point mutants were determined to be reasonably comparable to those on the wild type, which suggests that divalent cations passing through the TRPV1 channel use the same negatively charged amino acids as Ca(2+).
    Biological trace element research 12/2012; · 1.92 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The chemical synthesis of 4-N-carboxybutyl-5-fluorocytosine (II) in solution phase starting from 5-fluorocytosine and the solid phase synthesis of Arg-Gln-Trp-Arg-Arg-Trp-Trp-Gln-Arg-NH(2) attached to the 4-N-carboxybutyl-5-fluorocytosine residue at the N-terminus of the peptide (III) via peptide bond formation is reported. The target compound exhibited a significant cytotoxic activity against a culture of HepG2 cells. In addition our results demonstrated that this new compound affect cell viability, produce mitochondrial dysfunction as well as interfere with intracellular calcium homeostasis control; leading to cell malfunction and death.
    Bioorganic & medicinal chemistry letters 05/2012; 22(13):4233-7. · 2.65 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Bioassay-guided fractionation of the chloroform extract of Centaurea jacea L. afforded the isolation of cirsiliol, apigenin, hispidulin, eupatorin, isokaempferide, axillarin, centaureidin, 6-methoxykaempferol 3-methyl ether, trachelogenin, cnicin, 4'-acetylcnicin and three aliphatic glucose diesters, including the new natural product 1β-isobutanoyl-2-angeloyl-glucose. The structures of the compounds were established on the basis of spectroscopic analyses (UV, MS and NMR). All compounds were isolated for the first time from this species. The compounds were evaluated for their tumour cell growth inhibitory activities on HeLa, MCF-7 and A431 cells. Different types of secondary metabolites (flavonoids, sesquiterpenes) were found to be responsible for the antitumour effects of the extracts; the highest activity was exerted by centaureidin, in addition to moderately active compounds (cirsiliol, isokaempferide, apigenin, hispidulin, cnicin and 4'-acetylcnicin).
    Fitoterapia 04/2012; 83(5):921-5. · 2.23 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 29(31).
  • Z. SZENDI, G. DOMBI, I. VINCZE
    [Show abstract] [Hide abstract]
    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 28(12).
  • ChemInform 01/2010; 33(3).
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Phytochemical study of the aerial parts of Euphorbia pannonica led to the isolation of two new tigliane diterpenes, 4,12-dideoxy(4β)phorbol-20-benzoate-13-isobutyrate (1) and 4,12-dideoxy(4β)phorbol-20-benzoate-13-isovalerianate (2). The structures and relative stereochemistry were elucidated on the basis of extensive spectroscopic analyses, including 1D and 2D NMR experiments (1H NMR, JMOD, COSY, NOESY, HSQC and HMBC).
    Tetrahedron. 01/2009; 65(20):4013-4016.
  • Planta Medica - PLANTA MED. 01/2007; 73(09).
  • [Show abstract] [Hide abstract]
    ABSTRACT: Cyclohexene and tetralin can be oxidized to a slight extent by N2O in the presence of quaternary ammonium salt promoters under mild experimental conditions. In non-polar solutions, the higher yields of the oxidations of cyclohexene and tetralin are influenced by the donor–acceptor properties of the solvents. The changes in the IR spectrum of N2O lend further support to the assumption that ion-pair interactions between the solvated oxidant and the onium salts result in an enhanced rate of O-transfer from the oxidant. Onium-decavanadate ion-pair complexes are more effective promoters than simple onium salts.
    Journal of Molecular Catalysis A-chemical - J MOL CATAL A-CHEM. 01/2007; 263(1):48-54.
  • [Show abstract] [Hide abstract]
    ABSTRACT: A synthetic octapeptide, H-GlyGluGlyGluGlySerGlyGly-OH, and its phosphorylated Ser derivative were synthetized and their solution speciation and binding modes in their complexes with Al(III) were measured. One goal of the work was find a lead compound for the design of a selective peptide-based Al(III) chelator. pH-potentiometry was used to characterize the stoichiometry and the stability of the species formed in the interactions of the metal ion and the peptides, while multinuclear NMR was applied to characterize the binding sites of the metal ion in the complexes. CD spectroscopy revealed a difference in the conformational behaviour of the phosphorylated peptide as compared with its non-phosphorylated parent derivative. The Al(III) is presumed to enhance aggregation through the -PO3H(-)-Al(3+)-PO3(2-)-Al(3+)- intermolecular bindings between the peptide chains. The results of molecular dynamics calculations supported the experimentally obtained secondary structures and the binding position of Al(III).
    Journal of Inorganic Biochemistry 04/2006; 100(3):351-61. · 3.20 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The four possible stereoisomers of 3-methoxy-16-methyloestra-1,3,5(10)-trien-17-ol (1, 2, 3, 4) were converted into the corresponding 16-methyl-19-nortestosterone analogs (5, 6, 7, 8), which were characterized by their 1H- and 13C-NMR spectra. The coupling constants J16,17 and the characteristic 13C signals (C-12, C-17, C-18, 16-CH3) clearly confirmed the configurations at C-16 and C-17.
    Annalen der Chemie und Pharmacie 01/2006; 1993(8):923 - 925. · 3.10 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: 3-Hydroxy-2-hydroxymethyl- (2 and 3) and 3-hydroxymethyl-3-oxoandrostenes 4 were prepared from 2-hydroxymethylene derivatives 1. The configurations of the chiral centers were determined on the basis of chiroptical, spectroscopical, and X-ray analytical data. Furthermore, elimination reaction products (5, 6) were identified.2-(Hydroxymethyl)androsten-DerivateDie Herstellung der 3-Hydroxy-2-hydroxymethyl- (2 und 3) und 2-Hydroxymethyl-3-oxoandrostene 4 wird ausgehend von den 2-Hydroxymethylen-Verbindungen 1 beschrieben. Die Konfigurationen an den chiralen Zentren werden auf der Basis chiroptischer, spektroskopischer sowie Röntgenstruktur-analytischer Daten diskutiert. Ferner werden Produkte von Eliminierungsreaktionen identifiziert (5, 6).
    Annalen der Chemie und Pharmacie 01/2006; 1987(6):499 - 504. · 3.10 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The four possible isomers of 16-hydroxymethyl-3-methoxyestra-1,3,5(10)-trien-17-ol 5a, 6a, 7a, 8a were converted into the corresponding 16-methyl analogues 4a, 11a, 12a, 13a, which were characterized from their 1H- and 13C-NMR spectra. The results permit a configurational correlation with 16-methyl derivatives reported in the literature.
    Annalen der Chemie und Pharmacie 01/2006; 1990(5):419 - 422. · 3.10 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The complexation properties (including stoichiometries and stability constants of the complexes formed) of ethylenediaminetetramethylenephosphonic acid with AlIII and VIVO were studied in aqueous solution at an ionic strength of 0.2 M KCl, at 25 °C by means of pH potentiometry. For AlIII both mononuclear (AlLHn) and dinuclear (Al2LHn) species were found in solution, whereas for VIVO only mononuclear complexes were detected. For each metal ion, a solid complex was isolated at acidic pH and was characterized stoichiometrically. 1H and 31P NMR (for AlIII), UV/Vis and EPR (for VIVO) spectra were used to confirm the potentiometric results and to suggest the most probable binding mode of the complexes formed in solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
    Berichte der deutschen chemischen Gesellschaft 04/2004; 2004(12):2524 - 2532. · 2.94 Impact Factor

Publication Stats

220 Citations
94.39 Total Impact Points

Institutions

  • 1987–2013
    • University of Szeged
      • • Institute of Pharmaceutical Analysis
      • • Department of Organic Chemistry
      • • Institute of Pharmaceutical Chemistry
      • • Department of Pharmacognosy
      Szeged, Csongrad megye, Hungary
  • 1986
    • University of Turku
      • Department of Chemistry
      Turku, Province of Western Finland, Finland