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At least 271 records · Page 15Linked to original sources

PubMed2000

Validation of a LC method for the analysis of zafirlukast in a pharmaceutical formulation.

A reversed-phase high-performance liquid chromatographic (HPLC) method was developed and validated for estimation of zafirlukast in a pharmaceutical formulation. Assay samples were extracted utilizing acetonitrile. Drug and internal standard were chromatographed on reversed-phase C18 columns, using mixtures of acetonitrile/water and the eluents were monitored at different wavelengths. The method was validated statistically for its linearity, accuracy, robustness and precision. Experimental design was used during validation to evaluate method robustness and for the determination of intermediate precision. Factors examined for statistical approaches include laboratory, day, analyst, instrument, different percentage of organic modifier, temperature, wavelength and flow-rate. Due to its simplicity and accuracy, the method may be used for routine quality control analysis.

Anti-Asthmatic Agents↗

PubMedDate not supplied

Determination of medroxyprogesterone acetate in serum by HPLC with peroxyoxalate chemiluminescence detection using a fluorogenic reagent, 4-(N,N-dimethylaminosulphonyl)-7-hydrazino-2,1,3-benzoxadiazole.

The high-performance liquid chromatographic determination of medroxyprogesterone acetate (MPA) with peroxyoxalate chemiluminescence (PO-CL) detection is described. The spiked serum containing MPA was extracted on Bond-Elut C18 columns and derivatized with 4-(N,N-dimethylaminosulphonyl)-7-hydrazino-2,1,3-benzoxadiazole (DBD-H). The hydrazone of MPA with DBD-H was confirmed to be a mono-DBD-derivative. The reaction mixture was separated by direct injection onto a C18 analytical column, and quantified by PO-CL detection. The linear range of the standard curve, in serum, was 15.6-96.6 ng ml-1 with a detection limit of 9 ng ml-1 using only 100 microliters of serum, while the detection limit of standard MPA derivatized with DBD-H was 8.7 fmol per injection. The relative standard deviation of the method was 7.4% at 19.3 ng and 1.7% at 77.3 ng ml-1.

Chromatography, High Pressure Liquid↗

PubMed1989

Liposomes of enviroxime and phosphatidylcholine: definition of the drug-phospholipid interactions.

Interaction of the antiviral compound, enviroxime (E), with natural and synthetic phosphatidylcholines in organic and aqueous media was studied. Although insoluble in chloroform, E dissolved in chloroform solutions containing phosphatidylcholines. Solvation was directly related to the length of the fatty acid chains of the phospholipid. Proton spin resonance studies suggested an interaction of the fatty acid chains with the aromatic rings of E. Suspension of E-phosphatidylcholine mixtures of molar ratios up to 0.7:1.0 in aqueous media resulted in the formation of multilamellar liposomes. Liposomes containing E were more stable permeability barriers than those prepared with phospholipid alone, a property previously observed with cholesterol. Competition experiments suggested that E bound to the same sites in lipid bilayers as does cholesterol. These data indicate that E is incorporated into lipid bilayers of liposomes and that it alters the physical properties of the liposomes in a manner similar to that of cholesterol.

Benzimidazoles↗

PubMed2001

Simultaneous determination of the HIV protease inhibitors indinavir, amprenavir, saquinavir, ritonavir and nelfinavir in human plasma by high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatographic method for the simultaneous quantitative determination of five HIV protease inhibitors (i.e. indinavir, amprenavir, saquinavir, ritonavir and nelfinavir) in human plasma is described. An aliquot of 500 microl plasma was extracted with 0.5 ml of 0.1 M NH4OH and 5 ml of methyl tert.-butyl ether. After evaporating, the residue was dissolved in eluent mixture of acetonitrile and 50 mM KH2PO4 adjusted to pH 5.6 with 50 mM Na2HPO4 (43:57, v/v). Subsequently, the eluent was washed with hexane. Chromatography was performed using a C18 reversed-phase column. Ultraviolet detection at 215 nm was used. Linearity of the method was obtained in the concentration range of 0.05-20 microg ml(-1) for all five protease inhibitors. Our method is now in use to analyse plasma samples from patients treated with co-administration of HIV protease inhibitors.

Adult↗

PubMed1975

Neutral and Cationic Sulfonamido Derivatives of the Fluorescent Probe 2-p-Toluidinylnaphthalene-6-sulfonate. Properties and Mechanistic implications.

The sensitivity of the fluorescence energy of 2-p-toluidinylnaphthalene-6-sulfonate (TNS) to apparent solvent polarity is considerably greater in methanol-water mixtures and lower primary alcohols than in higher primary alcohols or solvents containing no hydroxyl groups. It is suggested that the behavior of TNS in lower alcohols and their mixtures with water is an anomalous result of the combination of general polarity influences and chanes in the nature of specific interactions of the probe with hydroxyl groups of such solvents. Upon conversion of the sulfonate group of TNS to sulfonamido, the biphasic behavior observed in alcohols is eliminated, and fluorescent probes are obtained which have more nearly equal sensitivites to polarity in the alcohols and nonhydroxyl solvents. The sulfonamido fluorescent probes are more sensitive to general environmental polarity than TNS, and are superior as probes of environmental polarity.

Binding Sites↗

PubMed1986

Synthesis and antiviral activity of sulfonamidobenzophenone oximes and sulfonamidobenzamides.

To find antiviral agents, various sulfonamidobenzophenone oximes (II) were synthesized from the appropriate m-sulfonamidobenzophenones by hydroxylamine reaction. The reaction products were generally obtained as syn/anti mixtures which were separable by fractional crystallization. The anti isomer had more potent antipoliovirus activity than the syn isomer. Various sulfonamidobenzamides (III) which were structurally related to II were synthesized by the reactions of amino-substituted benzamides with sulfuryl chloride or amines with (aminosulfonyl)benzoyl chloride. Antiviral activity was examined by the plaque-inhibition test. Compounds 5, 36, and 69 exhibited strong antipicornavirus activity. The structure-activity relationships are discussed.

Animals↗

PubMedDate not supplied

An acridinium sulphonylamide as a new chemiluminescent label for the determination of carboxylic acids in liquid chromatography.

The synthesis of a new acridinium sulphonylamide label for the liquid chromatographic determination of carboxylic acids is described. The label 10-methyl-N-(p-tolyl)-N-(p-iodoacetamidobenzenesulphonyl)-9-acr idi nium carboxamide iodide is synthesized from 9-acridine-carboxylic acid by a seven-step reaction. Ibuprofen, used as test compound, is coupled to the reactive iodoacetamide group of the label by means of an alkylation reaction in dry acetonitrile for 20 min at 50 degrees C in the presence of 18-crown-6 and potassium carbonate as base catalyst. The reaction mixture is injected into a liquid chromatographic system with chemiluminescence detection. Separation is performed on a Zorbax C18 column with acetonitrile-water-tetrahydrofuran (39:57:4, v/v/v) containing 10 mmol/L TBABr and 0.035% H2O2 as the mobile phase at a flow rate of 1.0 ml/min. Chemiluminescence detection is achieved by the post-column addition of 200 mmol/L potassium hydroxide dissolved in methanol-water (1:1, v/v) at a flow rate of 20 microL/min. The detection limit (S/N = 3) of derivatized ibuprofen is 60 pg (3 pg injected).

Acridines↗

PubMed1975

Construction of a colicin E1-R factor composite plasmid in vitro: means for amplification of deoxyribonucleic acid.

A composite plasmid has been constructed in vitro from colicin E1 factor (mass of 4.2 megadaltons [Md]) and nontransmissible resistance factor RSF 1010 (mass, 5.5. Md) deoxyribonucleic acids (DNAs) by the sequential action of Escherichia coli endonuclease (RI (Eco RI) and T4 phage DNA ligase on the covalently closed circular forms of the constituents. The composite plasmid was selected and amplified in vivo by sequential transformation of E. coli C600 with the ligated mixture and selection of transformants in medium containing streptomycin plus colicin E1, followed by amplification in the presence of chloramphenicol and purification of the extracted plasmid by dye-buoyant density gradient centrifugation in ethidium bromide-cesium chloride solution. Treatment of the composite plasmid with Eco RI yielded two fragments with mobilities corresponding to the linear forms of the parental plasmids, whereas Serratia marscesens endonuclease R (SmaR), which introduces a single scission in the colicin E1 factor but not in RSF 1010, convErted the composite plasmid to a single linear molecule (mass, 9.7 Md). Sequential degradation of colicin E1 factor with Sma R and Eco RI produced two fragments with masses of 3.5 and 0.7 Md; sequential degradation of RSF 1010 produced only one fragment (due to the cleavage with Eco RI), and sequential degradation of the composite plasmid produced the expected three fragments--an RSF 1010 Eco RI linear and the two expected products from the colicin E1 factor moiety. The composite plasmid conferred on the host cell resistance to streptomycin, sulfonamides, and colicin E1, but colicin E1 itself was not synthesized. In contrast, colicin E1 was synthesized by cells containing simultaneously both colicin E1 factor and RSF 1010 as separate entities. In the presence of chloramphenicol, the composite plasmid continued to replicate for 6 h. whereas replication of RSF 1010 and chromosomal DNA stopped within 2 h. Continued replication in the presence of chloramphenicol suggests that the replicator of the colicin E1 factor is functional in the composite plasmid.

Cell Fractionation↗

PubMed2003

Photochemical stability of nimesulide.

HPLC and TLC methods for monitoring of the photochemical stability of nimesulide are presented. Solution of nimesulide sodium salt was exposed to the light of wavelengths 254 nm. The presence of degradation products (2-phenoxy4-nitroaniline and methanesulfonic acid) was observed. In the exposed sample, 2-phenoxy4-nitroaniline was detected by HPLC analysis and sulfonic acid was detected by TLC analysis. An isocratic HPLC chromatographic condition was described for determination of nimesulide in a presence of its degradation product. The sample was analysed on Separon SGX, C(18), 250 x 4.6 i.d. 7 microm analytical column. The mobile phase was consisted of a mixture of acetonitrile and ammonium phosphate (pH 7.9; 0.02 M) (35:65 v/v). UV detector was performed at 245 nm. Propylparaben was employed as an internal standard. Standard area response was linear respect to concentration of nimesulide over range 150-500 microg/ml. As a validation of the method, the accuracy and between-day precision were done. The detection limit of 2-phenoxy4-nitroaniline was 0.12 microg/ml. The solvent system for TLC analysis was consisted of ethylacetate and cyclohexane (45:55), the samples were plotted on silica gel UV-254 nm. UV lamp (254 nm) and the chemical detection were used.

Chromatography, High Pressure Liquid↗

PubMed2006

Determination of valdecoxib in serum using a HPLC-diode array detector and its application in a pharmacokinetic study.

A simple, sensitive, isocratic and reproducible reversed phase HPLC method for the determination of valdecoxib, a novel specific COX-2 inhibitor in human serum was developed using a diode array detector and celecoxib as internal standard. The system consisted of a C18 column and a detector set at 240 nm. The mobile phase was a mixture of acetonitrile:water acidified to pH 3.2 with orthophosphoric acid (OPA) (60:40) pumped at room temperature and a flow rate of 1 ml/min. The mean absolute recovery value was about 90%, while the intra (n = 5) and inter (n = 5) assay variations were <18%. The calibration was linear over a concentration range of 20 ng/ml to 200 microg/ml with r2 > 0.999. The limit of detection was < or = 10 ng/ml. The method was used to study the pharmacokinetics of valdecoxib after a single dose oral administration to human volunteers.

Adult↗

PubMed2006

Synthesis of a chelating hexadentate ligand with a P3N3 donor set. Crystal and molecular structure of [OC-6-22]-[Co{(RP,RP,RP*)-CH3C(CH2PPhC6H4NH2-2)3}](PF6)3.

The first structurally authenticated example of a hexadentate chelating tertiary phosphine in which all six donors are bound to a single metal centre is described. The multidentate ligand (RP*,RP*,RP*)- and (RP*,RP*,SP*)-CH3C(CH2PPhC6H4NH2-2)3 has been prepared in 80% yield via the reaction of five equivalents of sodium (2-aminophenyl)phenylphosphide (generated in situ from (2-aminophenyl)phenylphosphine and sodium in thf) with 1,1,1-tri(bromomethyl)ethane in thf. The diastereomeric mixture has been complexed to cobalt(III) and the resulting pair of complexes, viz. [Co{(RP*,RP*,RP*)-CH3C(CH2PPhC6H4NH2-2)3}]Cl3 and [CoCl{(RP*,RP*,SP*)-CH3C(CH2PPhC6H4NH2-2)3}]Cl2, separated by ion exchange chromatography. The structure of the former (as the corresponding hexafluorophosphate salt) has been confirmed by X-ray crystallography and clearly shows all six donors of the P3N3 ligand coordinated to a single cobalt(III) centre. The related hexadentate ligand with internal N donors and terminal diphenylphosphino groups, viz. CH3C(CH2NHC6H4PPh2-2)3, has also been synthesised, albeit in low yield, via the reaction of [Li(tmeda)][2-NHC6H4PPh2] (generated in situ from (2-aminophenyl)diphenylphosphine, n-butyllithium and tmeda in diethyl ether) with 1,1,1-tri(iodomethyl)ethane in thf. No formation of a P3N3 ligand has been observed when either Na[2-PPhC6H4NH2] or [Li(tmeda)][2-NHC6H4PPh2] is reacted with the related tripodal substrate 1,1,1-tris(tolyl-4-sulfonyloxymethyl)ethane in thf. Rather the P-methyloxetane (+/-)-[3-{(2-aminophenyl)phenylphosphinomethyl}]-3-methyloxetane and the sulfonamide 2-(4-CH3C6H4SO2)NHC6H4PPh2 and the corresponding N-methyloxetane [3-{(2-diphenylphosphinophenyl)aminomethyl}]-3-methyloxetane have been isolated from the respective reactions. The structure of the sulfonamide has been confirmed by an X-ray analysis of the platinum(II) complex trans-[PtCl(CH3){2-PPh2C6H4NH(SO2C6H4CH(3-4)}2].

Journal Article↗

PubMedDate not supplied

Capillary electrophoretic behavior of seven sulfonylureas.

The electrophoretic behavior of seven sulfonylureas (bensulfuron methyl, sulfometuron methyl, nicosulfuron [accent], chlorimuron ethyl, thifensulfuron methyl [harmony], metsulfuron methyl, and chlorsulfuron) was studied under capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) conditions. Mixtures of these compounds were separated with very high efficiencies (2 x 10(5) theoretical plates) in a running buffer consisting of 3 parts acetate buffer (25 mM, pH 5.0) and 1 part acetonitrile. In this buffer system, acetonitrile was shown to be superior to methanol, acetone, and ethanol as a nonpolar additive, but any of these solvents can be used to reduce electroosmotic flow (EOF) and to obtain adequate separation. On-column detection limits at 214 nM were of the order of 80-100 fM. Micellar agents such as sodium dodecyl sulfate (SDS) and sodium cholate (but not monosialoganglioside-Gm1 or starburst dendrimer, generation 2.5) improved separation in phosphate and borate buffers. Implications of these results for the development of methods to detect these compounds on matrices of environmental origin are discussed. In particular, the instability of these compounds in methanol is noted and degradation products are detected using free zone CE. The methanolysis products of sulfometuron are tentatively identified by tandem MS (negative ion conditions) as 2-amino-4,6-dimethylpyrimidine and 2-carboxymethylbenz(N-carboxymethyl)sulfonamide.

Chromatography↗

PubMed1995

An inhibitor of cyclic AMP-dependent protein kinase enhances the superoxide production of human neutrophils stimulated by N-formyl-methionyl-leucyl-phenylalanine.

Intact human neutrophils produced superoxide (O2-) by the stimulation with N-formyl-methionyl-leucyl-phenylalanine (fMLP) even when the extracellular Ca2+ was absent (0.56 +/- 0.13 nmol/min per 10(6) cells). The production by fMLP was enhanced more than twice in the presence of the extracellular Ca2+. Moreover, the O2- production by fMLP in the presence of extracellular Ca2+ was enhanced nearly three times by the treatment of cells with H-89, an inhibitor of cyclic AMP-dependent protein kinase (PKA). The enhancement was not observed when the extracellular Ca2+ was depleted from the reaction mixture. In addition, H-89 did not enhance fMLP-induced O2- production of electropermeabilized neutrophils in which the intracellular Ca2+ concentration was fixed to about 100 nM. These observations suggest that not only Ca2+ influx but the inhibition of PKA is necessary for the maximum O2- production by fMLP and that the O2- production is partially suppressed by the activation of PKA induced by fMLP.

Bucladesine↗

PubMed2002

Effects of Ginkgetin from Ginkgo biloba Leaves on cyclooxygenases and in vivo skin inflammation.

Ginkgetin, a biflavone from Ginkgo biloba leaves, was previously reported to be a phospholipase A2 inhibitor and this compound showed the potent antiarthritic activity in rat adjuvant-induced arthritis as well as analgesic activity. This investigation was carried out to find effects on cyclooxygenase (COX)-1 and -2 including an in vivo effect. Ginkgetin (1 - 10 microM) and the biflavonoid mixture (10 - 50 microg/ml), mainly a 1 : 1 mixture of ginkgetin and isoginkgetin, from G. biloba leaves, inhibited production of prostaglandin E2 from lipopolysaccharide-induced RAW 264.7 cells. This inhibition was mediated, at least in part, by down-regulation of COX-2 expression, but not by direct inhibition of COX-1 or COX-2 activity. Down-regulation of COX-2 by ginkgetin was also proved in the dorsal skin of ICR mouse treated by 12-O-tetradecanoylphorbol 13-acetate (TPA). At total doses of 1,000 microg/site on the dorsal skin (15 mm x 15 mm), ginkgetin inhibited prostaglandin E2 production by 65.6 % along with a marked suppression of COX-2 induction. In addition, ginkgetin and the biflavonoid mixture (100 - 1,000 microg/ear) dose-dependently inhibited skin inflammation of croton oil induced ear edema in mice by topical application. The present study suggests that ginkgetin from G. biloba leaves down-regulates COX-2 induction in vivo and this down-regulating potential is associated with an anti-inflammatory activity against skin inflammatory responses.

Animals↗

PubMed2006

Analysis of five HMG-CoA reductase inhibitors-- atorvastatin, lovastatin, pravastatin, rosuvastatin and simvastatin: pharmacological, pharmacokinetic and analytical overview and development of a new method for use in pharmaceutical formulations analysis and in vitro metabolism studies.

A specific, accurate, precise and reproducible high-performance liquid chromatographic (HPLC) method was developed and validated for the simultaneous quantitation of five 3-hydroxy-3-methyglutaryl coenzyme A (HMG-CoA) reductase inhibitors, viz. atorvastatin, lovastatin, pravastatin, rosuvastatin and simvastatin, in pharmaceutical formulations and extended the application to in vitro metabolism studies of these statins. Ternary gradient elution at a flow rate of 1 mL/min was employed on an Intertisl ODS 3V column (4.6 x 250 mm, 5 microm) at ambient temperature. The mobile phase consisted of 0.01 m ammonium acetate (pH 5.0), acetonitrile and methanol. Theophylline was used as an internal standard (IS). The HMG-CoA reductase inhibitors and their metabolites were monitored at a wavelength of 237 nm. Drugs were found to be 89.6-105.6% of their label's claim in the pharmaceutical formulations. For in vitro metabolism studies the reaction mixtures were extracted with simple liquid-liquid extraction using ethyl acetate. Baseline separation of statins and their metabolites along with IS free from endogenous interferences was achieved. Nominal retention times of IS, atorvastatin, lovastatin, pravastatin, rosuvastatin and simvastatin were 7.5, 17.2, 21.6, 28.5, 33.5 and 35.5 min, respectively. The proposed method is simple, selective and could be applicable for routine analysis of HMG-CoA reductase inhibitors in pharmaceutical preparations as well as in vitro metabolism studies.

Animals↗

PubMed1993

A modification of the extended Hildebrand approach to predict the solubility of structurally related drugs in solvent mixtures.

A modification of the extended Hildebrand equation is proposed to estimate the solubility of an organic drug in solvent mixtures. The equation accurately reproduces the solubility of four sulphonamides in dioxane-water mixtures without requiring the heat of fusion of the solute. A single equation is obtained for predicting the solubility of related drugs using the solubilities of the drugs in the pure solvents, dioxane and water, and solute-solvent interaction terms consisting of the solubility parameter, delta 2, of the solute and the solubility parameter, delta 1, and basic partial solubility parameter, delta 1b, of the solvent mixture. By this procedure a single equation was obtained to estimate the solubilities of three xanthines in dioxane-water and another equation to obtain the solubilities of four sulphonamides. The equation obtained for sulphonamides is able to predict the experimental solubilities of two parent compounds, sulphasomidine and sulphathiazole, and the solubilities of a drug of different structure, p-hydroxybenzoic acid. This suggests that the intermolecular solute-solvent interaction of sulphonamides and p-hydroxybenzoic acid are similar. The results indicate that the solubility behaviour of drugs having different structures may be modelled using a common equation provided that they show similar solute-solvent interactions.

Dioxanes↗

PubMed1985

Topical cerium nitrate prevents postburn immunosuppression.

Suppression of cell-mediated immunity (CMI) follows a major thermal injury and is associated with an increased incidence of serious infections. Adult female CF-1 mice received a 20% full-thickness steam burn and were then treated with various topical antimicrobial creams in an attempt to alter the course of postburn immunosuppression. Topical agents included cerium nitrate (CE), silver sulfadiazine (SSD), mafenide (SML), silver nitrate (AG), and a mixture of CE and SSD (CE-SSD). CMI was determined in vivo by measuring ear swelling in response to 2,4-dinitrofluorobenzene (DNFB) challenge in previously sensitized mice. The usual nadir in CMI (ear swelling) when mice were sensitized at day 14 postburn did not occur in burned mice treated with CE or CE-SSD, AG was only modestly effective, and SML or SSD failed to restore CMI. These studies suggest that topical CE may have potential as an immunomodulator in the treatment of burns.

Animals↗

PubMed1992

Effects of ibutilide fumarate, a novel antiarrhythmic agent, and its enantiomers on isolated rabbit myocardium.

Ibutilide fumarate is currently in Phase II clinical trials for the treatment of life-threatening cardiac arrhythmias. The cardiovascular effects of ibutilide and its d- and l-stereoisomers, U82208E and U82209E were tested in an isolated rabbit myocardium system. In a series of repeated measures experiments, threshold, effective refractory period, force of contraction, conduction time and rate were measured at various pacing frequencies in isolated papillary muscles, ventricular muscle strips and right atria exposed to 10(-7), 10(-6) and 10(-5) M drug. Although there were occasional instances where one form had a greater or lesser effect on a given parameter, overall there was little pharmacological difference between the racemic mixture and its constituent forms. At the highest dose, effective refractory periods at 1 and 3 Hz increased by 18-32 ms, conduction times measured at 3 Hz increased by 27-30% and atrial rate decreased by 19-32%, while threshold and force of contraction were generally unaffected. In this study there were no clear cut pharmacologic differences between the three forms of this class III antiarrhythmic agent. Parallel studies to determine pA2 values of ibutilide and sotalol demonstrated that ibutilide possesses weak beta-adrenoceptor blocking properties.

Adrenergic beta-Antagonists↗