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Journal of Chromatography. A Jul 2018The presence of anionic free silanols in the silica-based stationary phases gives rise to broad and asymmetrical peaks when cationic basic compounds are chromatographed...
The presence of anionic free silanols in the silica-based stationary phases gives rise to broad and asymmetrical peaks when cationic basic compounds are chromatographed using hydro-organic mobile phases. The addition to the mobile phase of a reagent with ionic character prevents the access of analytes to the free silanols, improving the peak shape. The silanol activity can be affected by the buffer concentration and mobile phase pH, factors that are not always considered sufficiently in the literature. In this work, the chromatographic behaviour of three basic β-adrenoceptor antagonists (acebutolol, nadolol and timolol), using mobile phases containing acetonitrile, was examined at different phosphate buffer concentrations (5-50mM) and mobile phase pH (2-8), in the absence and presence of three imidazolium-based ionic liquids (1-ethyl-, 1-butyl- and 1-hexyl-3-methylimidazolium chloride). All factors were evaluated through both the retention and peak shape. The imidazolium cations can block the access of cationic analytes through electrostatic interaction with the anionic silanols, or association with the alkyl chains bound to the stationary phase. In previous reports, the protection mechanism was demonstrated to be directly related to the cation size. The studies in this work reveal that the effectiveness of the mobile phase additive as silanol blocker also depends on the concentration of the buffer anion and the protonation degree of the silanols on the stationary phase. Increasing amounts of phosphate at low pH give rise to increasing retention times. Also, the peak shape is improved, which indicates the influence of phosphate on blocking the activity of free silanols. However, the benefits obtained by the combined effect of buffering the mobile phase at low pH and the use of a bulky additive are lost at pH>6.
Topics: Buffers; Chromatography, Reverse-Phase; Hydrogen-Ion Concentration; Ionic Liquids; Phosphates; Silanes; Static Electricity
PubMed: 28602502
DOI: 10.1016/j.chroma.2017.05.061 -
Comparative Biochemistry and... Sep 2017Adrenaline changes expression of the genes encoding peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α), which is known as a regulator of... (Comparative Study)
Comparative Study
Adrenaline changes expression of the genes encoding peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α), which is known as a regulator of muscle size, and atrogin-1/muscle atrophy F-box (MAFbx), which is a muscle-specific ubiquitin ligase. However, the subtype of β-adrenergic receptor (β-AR) involved in regulating these genes in skeletal muscle is not yet well defined. In this study, the effects of intraperitoneal injection of adrenaline and three β-AR selective agonists on chick skeletal muscle metabolism were examined, to evaluate the functions of β-AR subtypes. Adrenaline decreased atrogin-1/MAFbx mRNA levels accompanied by an increase in PGC-1α mRNA and protein levels. However, among the three selective agonists, only the β-AR agonist, dobutamine, increased PGC-1α mRNA and protein levels, while the β-AR agonist, clenbuterol, suppressed atrogin-1/MAFbx mRNA levels. In addition, preinjection of the β-AR antagonist, acebutolol, and the β-AR antagonist, butoxamine, inhibited the adrenaline-induced increase in PGC-1α mRNA levels and the decrease in atrogin-1/MAFbx mRNA levels, respectively. Compared with adrenaline administration, the β-AR agonist, BRL37344, decreased PGC-1α mRNA levels and increased atrogin-1/MAFbx mRNA levels. These results suggest that, in chick skeletal muscle, PGC-1α is induced via the β-AR, while atrogin-1/MAFbx is suppressed via the β-AR.
Topics: Animals; Chickens; Gene Expression Regulation; Male; Muscle Proteins; Muscle, Skeletal; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; RNA, Messenger; Receptors, Adrenergic, beta-1; Receptors, Adrenergic, beta-2
PubMed: 28578076
DOI: 10.1016/j.cbpa.2017.05.013 -
Biomedical Chromatography : BMC Jul 2017This paper presents a method for the determination of acebutolol, betaxolol, bisoprolol, metoprolol, nebivolol and sotalol in human serum by liquid-liquid extraction and...
This paper presents a method for the determination of acebutolol, betaxolol, bisoprolol, metoprolol, nebivolol and sotalol in human serum by liquid-liquid extraction and ultra-high-performance liquid chromatography coupled with ultra-high-resolution TOF mass spectrometry. After liquid-liquid extraction, beta blockers were separated on a reverse-phase analytical column (Acclaim RS 120; 100 × 2.1 mm, 2.2 μm). The total run time was 6 min for each sample. Linearity, limit of detection, limit of quantification, matrix effects, specificity, precision, accuracy, recovery and sample stability were evaluated. The method was successfully applied to the therapeutic drug monitoring of 108 patients with hypertension. This method was also used for determination of beta blockers in 33 intoxicated patients.
Topics: Adrenergic beta-Antagonists; Chromatography, High Pressure Liquid; Female; Humans; Limit of Detection; Male; Mass Spectrometry; Middle Aged; Reference Standards; Reproducibility of Results
PubMed: 27925253
DOI: 10.1002/bmc.3911 -
Clujul Medical (1957) 2016Beta-adrenergic antagonists have been established as first line treatment in the medical management of hypertension, acute coronary syndrome and other cardiovascular...
BACKGROUND AND AIM
Beta-adrenergic antagonists have been established as first line treatment in the medical management of hypertension, acute coronary syndrome and other cardiovascular diseases, as well as for the prevention of initial episodes of gastrointestinal bleeding in patients with cirrhosis and esophageal varices, glaucoma, and have recently become the main form of treatment of infantile hemangiomas. The aim of the present study is to calculate for 14 beta-blockers several quantum chemical descriptors in order to interpret various molecular properties such as electronic structure, conformation, reactivity, in the interest of determining how such descriptors could have an impact on our understanding of the experimental observations and describing various aspects of chemical binding of beta-blockers in terms of these descriptors.
METHODS
The 2D chemical structures of the beta-blockers (14 molecules with one stereogenic center) were cleaned in 3D, their geometry was preoptimized using the software MOPAC2012, by PM6 method, and then further refined using standard settings in MOE; HOMO and LUMO descriptors were calculated using semi-empirical molecular orbital methods AM1, MNDO and PM3, for the lowest energy conformers and the quantum chemical descriptors (HLG, electronegativity, chemical potential, hardness and softness, electrophilicity) were then calculated.
RESULTS
According to HOMO-LUMO gap and the chemical hardness the most stable compounds are alprenolol, bisoprolol and esmolol. The softness values calculated for the study molecules revolve around 0.100. Propranolol, sotalol and timolol have among the highest electrophilicity index of the studied beta-blocker molecules. Results obtained from calculations showed that acebutolol, atenolol, timolol and sotalol have the highest values for the electronegativity index.
CONCLUSIONS
The future aim is to determine whether it is possible to find a valid correlation between these descriptors and the physicochemical behavior of the molecules from this class. The HLG could be correlated to the experimentally recorded electrochemical properties of the molecules. HOMO could be correlated to the observed oxidation potential, since the required voltage is related to the energy of the HOMO, because only the electron from this orbital is involved in the oxidation process.
PubMed: 27857521
DOI: 10.15386/cjmed-610 -
European Journal of Drug Metabolism and... Jun 2017The US Food and Drug Administration, World Health Organization and European Medicines Agency have allowed biowaiver for some BCS class III drugs, but shortened the...
BACKGROUND AND OBJECTIVES
The US Food and Drug Administration, World Health Organization and European Medicines Agency have allowed biowaiver for some BCS class III drugs, but shortened the requisite dissolution time of BCS class III drugs from 30 to 15 min, considering their site-specific absorption and others risk. The objective of this study was to assess the effects of site-specific absorption, low absorbed fraction (F ) and gastric emptying rate on the biowaiver extension of BCS class III drugs.
METHODS
The oral absorption of BCS class III drugs nadolol, acebutolol and atenolol which were P-gp substrates, was simulated using GastroPlus software with physiological parameters reflecting site-specific and site-independent absorption. Then, the simulation results were compared with the experimental data in literature. Simulation with different dissolution rates (>85 % solubility, T = 15-180 min) was performed to predict absorption (maximum concentration, C and area under the concentration-time curve from time 0 to infinity, AUC) of the above model/virtual drugs (F 3.81-80.14 %).
RESULTS
The results of this study indicated that the site-specific absorption and low F magnified the effect of dissolution rate on C and AUC. However, the oral absorption of model drugs was not sensitive to the change of gastric emptying rate from 0.1, 0.25, 0.5 to 1 h.
CONCLUSIONS
Based on the results of this study, we suggest that for BCS class III drug with high F (about >80 %), the biowaiver should extend to rapid dissolution (T = 30 min), and 30 % of F as the boundary of intermediate permeability class (30 % < F < 85 %).
Topics: Computer Simulation; Gastrointestinal Tract; Humans; Intestinal Absorption; Models, Biological; Permeability; Phenoxypropanolamines; Software
PubMed: 27447171
DOI: 10.1007/s13318-016-0361-2 -
Archiv Der Pharmazie Sep 2016The structure-activity relationships of 13 analogs of aryloxyaminopropanol type derived from 2-hydroxyphenylethanone as potential β-blockers are described. The...
The structure-activity relationships of 13 analogs of aryloxyaminopropanol type derived from 2-hydroxyphenylethanone as potential β-blockers are described. The synthesized compounds possess an isopropyl or a tert-butyl group in the hydrophilic part of the molecule and an alkoxymethyl substitution in the lipophilic moiety. The target compounds were prepared by an established four-step method and their structures were confirmed by interpretation of their UV, IR, (1) H NMR and (13) C NMR spectra, and by elemental analysis. The β-adrenolytic efficacy of the prepared racemic compounds was determined on isolated guinea pig atria (β1 ) and trachea (β2 ) and expressed as pA2 values against isoprenaline tachycardia. The assumed cardioselectivity was expressed as β1 /β2 ratio and the values of compounds with an alkoxy group (CH3 O, iC3 H5 O, C5 H11 O, CH2 CHCH2 O, CH3 OCH2 CH2 O) in the lipophilic part and with tert-butyl in the hydrophilic part of the molecule were found to be comparable or higher than those of the standards acebutolol and celiprolol. All evaluated substances at a concentration of 10(-7) mol/dm(3) showed also negative chronotropic effects.
Topics: Acebutolol; Adrenergic beta-Antagonists; Animals; Celiprolol; Guinea Pigs; Heart Atria; Heart Rate; Histamine; Isoproterenol; Propanolamines; Structure-Activity Relationship; Trachea
PubMed: 27417385
DOI: 10.1002/ardp.201600136 -
Physical Chemistry Chemical Physics :... Jun 2016(14)N ultra-wideline (UW), (1)H{(15)N} indirectly-detected HETCOR (idHETCOR) and (15)N dynamic nuclear polarization (DNP) solid-state NMR (SSNMR) experiments, in...
(14)N ultra-wideline (UW), (1)H{(15)N} indirectly-detected HETCOR (idHETCOR) and (15)N dynamic nuclear polarization (DNP) solid-state NMR (SSNMR) experiments, in combination with plane-wave density functional theory (DFT) calculations of (14)N EFG tensors, were utilized to characterize a series of nitrogen-containing active pharmaceutical ingredients (APIs), including HCl salts of scopolamine, alprenolol, isoprenaline, acebutolol, dibucaine, nicardipine, and ranitidine. A case study applying these methods for the differentiation of polymorphs of bupivacaine HCl is also presented. All experiments were conducted upon samples with naturally-abundant nitrogen isotopes. For most of the APIs, it was possible to acquire frequency-stepped UW (14)N SSNMR spectra of stationary samples, which display powder patterns corresponding to pseudo-tetrahedral (i.e., RR'R''NH(+) and RR'NH2(+)) or other (i.e., RNH2 and RNO2) nitrogen environments. Directly-excited (14)N NMR spectra were acquired using the WURST-CPMG pulse sequence, which incorporates WURST (wideband, uniform rate, and smooth truncation) pulses and a CPMG (Carr-Purcell Meiboom-Gill) refocusing protocol. In certain cases, spectra were acquired using (1)H → (14)N broadband cross-polarization, via the BRAIN-CP (broadband adiabatic inversion - cross polarization) pulse sequence. These spectra provide (14)N electric field gradient (EFG) tensor parameters and orientations that are particularly sensitive to variations in local structure and intermolecular hydrogen-bonding interactions. The (1)H{(15)N} idHETCOR spectra, acquired under conditions of fast magic-angle spinning (MAS), used CP transfers to provide (1)H-(15)N chemical shift correlations for all nitrogen environments, except for two sites in acebutolol and nicardipine. One of these two sites (RR'NH2(+) in acebutolol) was successfully detected using the DNP-enhanced (15)N{(1)H} CP/MAS measurement, and one (RNO2 in nicardipine) remained elusive due to the absence of nearby protons. This exploratory study suggests that this combination of techniques has great potential for the characterization of solid APIs and numerous other organic, biological, and inorganic systems.
PubMed: 27314503
DOI: 10.1039/c6cp02855a -
Environmental Pollution (Barking, Essex... Jul 2016Adsorption of weakly basic compounds by sludge is poorly understood, although it has important implications on the distribution and fate of such micropollutants in...
Adsorption of weakly basic compounds by sludge is poorly understood, although it has important implications on the distribution and fate of such micropollutants in wastewater effluent and sludge. Additionally, many of these compounds are chiral, and it is likely that their interactions with sludge is stereoselective and that the process may be further modified by surfactants that coexist in these systems. Adsorption of (R) and (S)-enantiomers of five commonly used β-blockers, i.e., acebutolol, atenolol, metoprolol, pindolol and propranolol, on sludge was characterized through batch experiments. Stereoselectivity in adsorption increased with decreases in hydrophobicity of the β-blockers. The enantiomeric fraction (EF) of the amount of acebutolol, atenolol and metoprolol sorbed on sludge were 0.27, 0.55 and 0.32, respectively. Thus, Kd values of the (S)-enantiomers of acebutolol and metoprolol were approximately twice that of the (R)-enantiomer, that is, 109 ± 11 and 57 ± 8 L/kg compared to 52 ± 13 and 22 ± 8 L/kg, respectively. There was no statistically significant difference in Kd values of the enantiomers of pindolol and propranolol, suggesting stereoselectivity in adsorption was likely driven by specific polar interactions rather than hydrophobic interactions. The EF value of atenolol decreased from 0.55 ± 0.03 to 0.44 ± 0.04 after modifying the sludge with Triton X 100. These results suggested that surfactants altered adsorption of β-blockers to sludge, likely by forming ion pair complexes that promote hydrophobic interactions with the solid surfaces.
Topics: Adrenergic beta-Antagonists; Adsorption; Models, Chemical; Sewage; Stereoisomerism; Surface-Active Agents; Wastewater; Water Pollutants, Chemical; Water Purification
PubMed: 27155096
DOI: 10.1016/j.envpol.2016.04.091 -
British Journal of Clinical Pharmacology Aug 2016Peripheral vasoconstriction has long been described as a vascular adverse effect of β-adrenoceptor blockers. Whether β-adrenoceptor blockers should be avoided in... (Comparative Study)
Comparative Study Meta-Analysis Review
AIM
Peripheral vasoconstriction has long been described as a vascular adverse effect of β-adrenoceptor blockers. Whether β-adrenoceptor blockers should be avoided in patients with peripheral vascular disease depends on pharmacological properties (e.g. preferential binding to β1 -adrenoreceptors or intrinsic sympathomimetic activity). However, this has not been confirmed in experimental studies. We performed a network meta-analysis in order to assess the comparative risk of peripheral vasoconstriction of different β-adrenoceptor blockers.
METHOD
We searched for randomized controlled trials (RCTs) including β-adrenoceptor blockers that were published in core clinical journals in the Pubmed database. All RCTs reporting peripheral vasoconstriction as an adverse effect of β-adrenoceptor blockers and controls were included. Sensitivity analyses were conducted including possibly confounding covariates (latitude, properties of the β-adrenoceptor blockers, e.g. intrinsic sympathomimetic activity, vasodilation, drug indication, drug doses). The protocol and the detailed search strategy are available online (PROSPERO registry CRD42014014374).
RESULTS
Among 2238 records screened, 38 studies including 57 026 patients were selected. Overall, peripheral vasoconstriction was reported in 7% of patients with β-adrenoceptor blockers and 4.6% in the control groups (P < 0.001), with heterogeneity among drugs. Atenolol and propranolol had a significantly higher risk than placebo, whereas pindolol, acebutolol and oxprenolol had not.
CONCLUSION
Our results suggest that β-adrenoceptor blockers have variable propensity to enhance peripheral vasoconstriction and that it is not related to preferential binding to β1 -adrenoceptors. These findings challenge FDA and European recommendations regarding precautions and contra-indications of use of β-adrenoceptor blockers and suggest that β-adrenoceptor blockers with intrinsic sympathomimetic activity could be safely used in patients with peripheral vascular disease.
Topics: Adrenergic beta-Antagonists; Dose-Response Relationship, Drug; Humans; Randomized Controlled Trials as Topic; Sympathomimetics; Vasoconstriction; Vasodilation
PubMed: 27085011
DOI: 10.1111/bcp.12980