Search PubMed⌕ Search

Biomedical subjects

J Cizmárik

Publications and source records attributed to J Cizmárik.

At least 19 recordsLinked to original sources
PubMed2006

QSAR study of antimycobacterial activity of quaternary ammonium salts of piperidinylethyl esters of alkoxysubstituted phenylcarbamic acids.

A series of 17 halogenides of quaternary ammonium salts of the alkylpiperidinylethyl esters of 2-pentoxy (and 2-heptoxy) substituted phenylcarbamic acids were evaluated for in vitro antimycobacterial activity against Mycobacterium tuberculosis, M. kansasii, and M. avium. Correlation of this action with lipophilicity (log P, 1-octanol-water system) was used for the description of the structure-antimycobacterial activity relationships (QSARs). The activity increased with the increasing lipophilicity of the compounds.

Anti-Bacterial Agents↗
PubMed2006

[Interconversion of stereochemically unstable chiral drugs: utilization of chromatographic techniques for the study of enantiomerization. Part II: practical applications].

Enantiomerization is a first-order reaction; it means interconversion of one enantiomer into another (and vice versa). This phenomenon is a typical feature of some configurationally unstable chiral compounds and it complicates separation of racemic mixtures. For the study of enantiomerization, chromatographic separation techniques (GC, SFC, CE, MEKC, HPLC) and NMR can be used. Chromatographic methods suitable for investigation of enantiomerization include dynamic chromatography (if time scales of enantiomerization and separation are the same) and stopped-flow chromatography (time scales of both processes are different). The present paper surveys the research of enantiomerization from 1975, when papers describing enantiomerization in greater detail were published, to the present. Today, mathematical approaches and computer-assisted deconvolution procedures are commonly used for evaluation of enantiomerization--calculation of thermodynamic parameters (deltaGapp, deltaHapp, deltaSapp) and rate constants (klapp, k(-1)app). The aim of many publications was not only determination of the enantiomerization energy barrier, but the influence of the chiral stationary phase on enantiomerization was studied as well. In some cases, enantiomerization was used for preparative purposes--a pure enantiomer was obtained and thus complicated synthesis was excluded.

Chromatography↗
PubMed2006

[Natural derivatives of 4H-pyran-4-one].

The present review paper describes the natural derivatives of 4H-pyran-4-one (simple, benzo- and dibenzo-derivatives). It includes their origin, use, and particularly in the case of flavonoids their biological actions and therapeutic use.

Flavonoids↗
PubMed2006

[Interconversion of stereochemically unstable chiral drugs. Part III: Using beta-cyclodextrin as a chiral stationary phase for HPLC separation of diazepam conformers coupled with an off-line NMR experiment].

Chiral beta-cyclodextrin was used to separate diazepam conformers. Several mobile phases of the composition acetonitrile/acetate buffer 200 mmol/l (pH=3.3, 5.5, 6.5) were employed for this purpose. As follows, the influence of addition of chiral beta-cyclodextrin to the mobile phase on diazepam separation was studied. The interconversion was a concurrence process of separation, resulting from stereolability of the diazepam molecule. The influences of temperature, flow rate, pH, and ionic strength of the mobile phase on interconversion and chromatographic parameters (retention factor and selectivity coefficient) were studied. Complementary off-line NMR measurements were carried out with the goal to confirm the structure of diazepam in the presence of an acid mobile phase.

Chromatography, High Pressure Liquid↗
PubMed2005

Kinetic study of the degradation of a potential local anesthetic drug in serum using the DNA-based electrochemical biosensor.

DNA-drug association interaction at the DNA modified screen-printed electrode for 1-methyl-2-piperidinoethylester of 2-hexoxyphenylcarbamic acid was found leading to an accumulation of the drug within the DNA layer. A procedure for the determination of drug in blood serum matrix using the protein precipitation and voltammetric measurement of the electroactive drug with the DNA biosensor was obtained and an effort was done to apply it for an assay of the drug enzymatic degradation in human and rabbit sera at 37 degrees C.

Anesthetics, Local↗
PubMed2005

[Preformulation studies of potential drug XIX M: partition coefficient].

The factors which markedly influence availability of the drug from the dosage form include also auxiliary substances, which are an inevitable component in the formulation of the drug. In the selection of auxiliary substances for a newly formulated drug, it is necessary to know that the drug is never a simple mixture of mutually independent ingredients, but a dynamic system in which various physical and chemical processes take place. The present paper aims to study the effect of auxiliary substances from the group of humectants with graded concentrations and the effect of the preservative on the partition coefficient of potential drug XIX M. Partition coefficient (P') was estimated in the system n-octanol/aqueous solution with graded concentrations of polyols. In these estimations, n-octanol simulated the horny layer, and the aqueous solution the base of the topical preparation. The auxiliary substances employed were polyols - glycerol, propylene glycol, and sorbitol in 5, 10, 15, and 20% concentrations and an antimicrobially effective solution of Ajatin (Solution benzododecinii bromati) in two concentrations of 0.01 and 0.1 wt %. It follows from the obtained results that the values of partition coefficient of potential drug XIX M are greatly influenced by auxiliary substances. The value of this parameter, and therefore also biological availability, depend not only on the sort of the polyol used and its concentration, but also on the concentration of the preservative employed, in this case Ajatin.

Anesthetics, Local↗
PubMed2005

[HPLC separation of racemic basic esters of alkoxyphenylcarbamic acid using two teicoplanin chiral stationary phases].

This paper presents the results obtained with the use of two chiral stationary phases (CSP), based on a glycopeptide antibiotic agent--teicoplanin aglycone (CHIROBIOTIC TAG) and methylated teicoplanin aglycon m-TAG. Twenty-one racemic mixtures of 1-methyl-2-piperidinoethylesters of 2-, 3- and 4-alkoxyphenylcarbamic acid were examined. The investigation included interaction between separated substances and CSP, and the effect of separation of the enantiomers under study on the value of the resolution factor (R(ij)) under identical chromatographic conditions with the use of the method of high-performance liquid chromatography (HPLC). On the basis of obtained results, it is possible to report that CSP-CHIROBIOTIC TAG is more advantageous for these racemates, because it does not contain a saccharide part, with decrease the possibility of non-polar interactions which exert a negative effect on the R(ij) value.

Anti-Bacterial Agents↗
PubMed2005

[A study of physicochemical properties of 2-, 3-, 4-alkoxyphenylcarbamic acid derivatives with a substituted N-phenylpiperazine moiety in the basic part].

The paper presents the study of some physicochemical properties of 2-, 3-, 4-alkoxyphenylcarbamic acid derivatives with various substituted N-phenylpiperazin-1-yl moiety in the basic part of the molecule. Elemental analysis, melting point, solubility, surface activity, dissociation constant and some lipophilicity parameters i.e.--partition coefficient, capacity factor obtained from HPLC, and R(M) values from reversed-phase thin-layer chromatography were determined.

Chemical Phenomena↗
PubMed2005

[Interconversion of stereochemically unstable chiral drugs: utilization of chromatographic techniques for the study of enantiomerization, calculation of thermodynamic parameters. Part I: theoretical aspects].

The paper explains the theoretical aspects of the process of enantiomerization and describes its characteristic features (generation of a plateau). In addition, some complications are presented that are produced by enantiomerization either from analytical or pharmacological points of view. It also defines the way of how to calculate energy barriers of enantiomerization according to the methods used for the separation of racemic mixtures (stopped-flow or dynamic chromatography). Mathematic models useful in deconvolution of chromatograms are also described. With the use of dynamic methods it is not possible to quantitatively evaluate the obtained chtromatograms and calculate thermodynamic parameters without computer-assisted deconvolution.

Chromatography↗
PubMed2004

A new group of potential antituberculotics: hydrochlorides of piperidinylalkyl esters of alkoxy-substituted phenylcarbamic acids.

A group of 31 of alkoxy-substituted phenylcarbamic acids with the alkoxy group in ortho, meta or para position, and methyl or ethoxymethyl attached to the ethylene moiety in position 1, including both basic ethyl esters and derivatives branched on ethylene, were evaluated for in vitro antimycobacterial activity against Mycobacterium tuberculosis, M. kansasii, and M. avium. To describe the structure-antimycobacterial activity relationships (QSARs), an approach based on a combination of the Free-Wilson analysis was used to express the influence of the substituents on the ethylene group as well as the position of the alkoxy groups on the phenyl ring and of the hydrophobicity of alkyls. In vitro antimycobacterial activity becomes higher with increasing hydrophobic properties of the alkoxy groups. The para- and meta-substituted derivatives were more active than the ortho-substituted ones. Substitution of ethylene in position 1 by methyl increased the activity against M. tuberculosis, a similar substitution by ethoxymethyl increased the activity against M. kansasii. The most active compounds were piperidinyl-1-(ethoxymethyl)ethylesters of heptoxyphenylcarbamic acids.

Antitubercular Agents↗
PubMed2004

Selectivity tuning of serially coupled (S,S) Whelk-O 1 and (R,R) Whelk-O 1 columns in HPLC.

The selectivity tuning of two columns coupled in series is investigated in chiral high-performance liquid chromatography. Two columns with reversal enantioselectivities [(R,R) Whelk-O 1 and (S,S) Whelk-O 1] are coupled in series via a T connector. Selectivity of such a column series is tuned by varying the mobile phase flows in the individual columns. The flow ratio necessary for the required selectivity is calculated on the basis of retention factors measured on the individual columns. The performance of this method for adjusting the required selectivity is studied by the separation of enantiomers of alkoxy substituted esters of phenylcarbamic acid. It is demonstrated that the change of the mobile phase flows in the individual columns enables change in the elution order of enantiomers.

Carbamates↗
PubMed2004

[Separation of enantiomers of phenylcarbamic acid derivatives by HPLC method].

The chiral stationary phase on the base of beta-cyclodextrin and the mobile phase acetonitrile/0.1 mol/l acetate buffer pH=5.2 (88/12 w/w) were used for the separation of the enantiomers of 1-methoxymethyl, 1-ethoxymethyl, 1-propoxymethyl-2-(1-pyrrolidinyl), (1-piperidino), (1-perhydroazepinyl)ethyl esters of 2-alkoxyphenylcarbamic acid. The influence of the structure of these compounds and the influence of temperature on enantioseparation were studied. The dominant effect on the resolution of enantiomers is exerted by the length of the alkoxysubstituent on the aromatic ring and its position with regard to the stereogenic centre. A decrease in temperature caused an increase in the retention factors of the compounds under study and the resolution values of enantiomers.

Anesthetics, Local↗
PubMed2004

[HPLC determination of diperodon enantiomers in blood serum by using teicoplanin chiral stationary phase].

The chiral stationary phase on the base of teicoplanin and the polar-organic mobile phase methanol/acetonitrile/acetic acid/triethylamine 45/55/0.3/0.2 was used for the separation of diperodon enantiomers. The developed method was suitable to determine the enantiomers in blood serum up to 0.5 microg/ml. The degradation of diperodon enantiomers was studied in serum by an in vitro method and the experimental rate constants were determined.

Chromatography, High Pressure Liquid↗
PubMed2003

Antimycobacterial activity of basic ethyl esters of alkoxy-substituted phenylcarbamic acids.

A series of 124 basic ethyl esters of alkoxy-substituted phenylcarbamic acids with the alkoxy group in position 2, 3 or 4 on the phenyl ring, and basic substituents attached to the ethyl moiety in position 2, were evaluated for in vitro antimycobacterial activity against strains of Mycobacterium tuberculosis, Mycobacterium kansasii and Mycobacterium avium. In vitro antimycobacterial activity becomes higher with increasing hydrophobic properties of the alkoxy groups. The p- and m-substituted derivatives were more active than the o-substituted ones. Direct relationship between the structure of the basic substituents and the activity was not found.

Antitubercular Agents↗
PubMed2003

Antimycobacterial activity of piperidinylpropyl esters of alkoxy-substituted phenylcarbamic acids.

A series of 17 hydrochlorides of piperidinylpropyl esters of alkoxy-substituted phenylcarbamic acids with the alkoxy group in position 2, 3 or 4 on the phenyl ring, and basic substituents attached to the moiety in position 3, were evaluated for in vitro antimycobacterial activity against the strains of Mycobacterium tuberculosis, M. kansasii and M. avium. To describe the structure-antimycobacterial activity relationships (QSAR), an approach based on the Free-Wilson method was employed to express the differences between individual moieties (including propyl and ethyl). The change of ethyl to propyl moiety increases the activity to M. tuberculosis but decreases the antimycobacterial activity to all potentially pathogenic strains under study.

Alcohols↗
PubMed2003

Coupled column chromatography for separation and determination of enantiomers of phenylcarbamic acid derivatives in serum.

Columns packed with vancomycin coupled to an achiral C18 column and beta-cyclodextrin were used for the separation and the determination of enantiomers of alkoxysubstituted esters of phenylcarbamic acid in blood serum. The method involves off-line SPE, the separation of the racemate on a reversed-phase stationary phase, and the separation of the enantiomers on a chiral stationary phase. The limit of detection was 1.0 microg/ml for the vancomycin column and 10.0 microg/ml for the beta-cyclodextrin column in standard solution. In vitro degradation studies of enantiomers demonstrated a difference in the concentation of the enantiomers after the treatment. It was found that the rate constants of R(-)- and S(+)-forms of enantiomers are not significantly different.

Carbamates↗