Diazotization titrations in pharmacopoeial quality control of medicines and proposals for their revision in the European Pharmacopoeia.

Based on the data in the Ph. Eur., some other newer pharmacopoeias and published experimental papers propose to revise the text of Ph. Eur. 2.5.8. First, it is necessary to specify which of the electrometric methods should be used to indicate the endpoint of diazotization titrations in Ph. Eur. (preferable potentiometry with a platinum indicating electrode). The amount of potassium bromide in the titration solution may be reduced to 1 g, the cooling of the solution before titration may be omitted from the framework procedure, and it may be specified in individual monographs if necessary to obtain accurate and correct results for some medicines. Diazotization titration can be performed in Ph. Eur. and can also be used to determine the content of some other medicines.

Colour and content of some metals in honey.

The paper highlights the correlations between the results of instrumental colour measurement and the content of certain metals in kinds of honey. Sufficiently close correlations may lead to the development of procedures for the rapid determination of the content of these metals in honey by colour measurement without the need for more demanding sample preparation.

Colour and content of some biologically active substances in honey.

This paper highlights the correlations between instrumental measurements of colour and the content of some biologically active organic compounds (especially phenolics and flavonoids) in honey. Sufficiently close correlations may lead to the development of procedures for rapid determination of the content of these substances in honey by colour measurement without the need for more demanding sample preparation.

Colour and antioxidant activity of honey.

The paper highlights the relationships between the results of instrumental colour measurement and the results of the determination of the antioxidant activity of honey (especially by DPPH and FRAP). The sufficiently close correlations show that once verified, supplemented by regression analysis and calibration, they may find application in the rapid determination of the antioxidant activity of honey.

Telacebec (Q203): Is there a novel effective and safe anti-tuberculosis drug on the horizon?

High prevalence and stronger emergency of various forms of drug-resistant tuberculosis (DR-TB), including the multidrug-resistant (MDR-TB) as well as extensively drug-resistant (XDR-TB) ones, caused by variously resistant Mycobacterium tuberculosis pathogens, make first-line anti-tuberculosis (anti-TB) agents therapeutically more and more ineffective. Therefore, there is an imperative to develop novel highly efficient (synthetic) agents against both drug-sensitive-TB and DR-TB. The exploration of various heterocycles as prospective core scaffolds for the discovery, development and optimization of anti-TB drugs remains an intriguing scientific endeavour. Telacebec (Q203; TCB), a molecule containing an imidazo[1,2-a]pyridine-3-carboxamide (IPA) structural motif, is considered a novel very promising anti-TB agent showing a unique mechanism of action. The compound blocks oxidative phosphorylation by inhibiting a mycobacterial respiratory chain due to interference with a specific cytochrome b subunit (QcrB) of transmembrane bc1 menaquinol-cytochrome c oxidoreductase as an essential component for transporting electrons across the membrane from menaquinol to other specific subunit, cytochrome c (QcrC). Thus, the ability of mycobacteria to synthesize adenosine-5´-triphosphate is limited and energy generating machinery is disabled. The TCB molecule effectively fights drug-susceptible, MDR as well as XDR M. tuberculosis strains. The article briefly explains a mechanism of an anti-TB action related to the compounds containing a variously substituted IPA scaffold and is focused on their fundamental structure-anti-TB activity relationships as well. Special consideration is paid to TCB indicating the importance of particular structural fragments for maintaining (or even improving) favourable pharmacodynamic, pharmacokinetic and/or toxicological properties. High lipophilicity of TCB might be regarded as one of the key physicochemical properties with positive impact on anti-TB effect of the drug. In January 2021, the TCB molecule was also involved in phase-II clinical trials focused on the treatment of Coronavirus Disease-19 caused by Severe Acute Respiratory Syndrome Coronavirus 2.

Analysis of positional isomers of 2-3-4-alkoxyphenylcarbamic acid derivatives by a combination of TLC and IMS.

In this study, we have demonstrated a separation of positional isomers of some derivatives of alkoxyphenylcarbamic acid. These compounds belong to drugs with local anesthetics activity. The low volatility compounds were analysed by a Thin Layer Chromatography (TLC) and Ion Mobility Spectrometry (IMS) using diode laser desorption for sample introduction to IMS. This combined approach allowed the identification of compounds. Also, we have carried out IMS studies of all compounds and determined their ion mobilities The ion mobilities were increasing with the geometry change from position ortho to para of alkoxy chain, which is in agreement with their different collision cross section (CCS).

Colour and content of some biologically active substances in natural products and products of natural origin.

The paper draws attention to the correlations between the results of instrumental colour measurements and the content of some biologically active organic substances (carotenoids, chlorophyll, anthocyanins, curcuminoids, etc.) in natural products and products of natural origin. After supplementation by regression analysis and calibration, sufficiently close correlations can lead to the development of procedures for rapid determination of the content of these substances and their groups by colour measurement without more demanding sample treatment.

Telacebec (Q203): Is there a novel effective and safe anti-tuberculosis drug on the horizon?

High prevalence and stronger emergency of various forms of drug-resistant tuberculosis (DR-TB), including the multidrug-resistant (MDR-TB) as well as extensively drug-resistant (XDR-TB) ones, caused by variously resistant Mycobacterium tuberculosis pathogens, make first-line anti-tuberculosis (anti-TB) agents therapeutically more and more ineffective. Therefore, there is an imperative to develop novel highly efficient (synthetic) agents against both drug-sensitive-TB and DR-TB. The exploration of various heterocycles as prospective core scaffolds for the discovery, development and optimization of anti-TB drugs remains an intriguing scientific endeavour. Telacebec (Q203; TCB), a molecule containing an imidazo[1,2-a]pyridine-3-carboxamide (IPA) structural motif, is considered a novel very promising anti-TB agent showing a unique mechanism of action. The compound blocks oxidative phosphorylation by inhibiting a mycobacterial respiratory chain due to interference with a specific cytochrome b subunit (QcrB) of transmembrane bc1 menaquinol-cytochrome c oxidoreductase as an essential component for transporting electrons across the membrane from menaquinol to other specific subunit, cytochrome c (QcrC). Thus, the ability of mycobacteria to synthesize adenosine-5´-triphosphate is limited and energy generating machinery is disabled. The TCB molecule effectively fights drug-susceptible, MDR as well as XDR M. tuberculosis strains. The article briefly explains a mechanism of an anti-TB action related to the compounds containing a variously substituted IPA scaffold and is focused on their fundamental structure-anti-TB activity relationships as well. Special consideration is paid to TCB indicating the importance of particular structural fragments for maintaining (or even improving) favourable pharmacodynamic, pharmacokinetic and/or toxicological properties. High lipophilicity of TCB might be regarded as one of the key physicochemical properties with positive impact on anti-TB effect of the drug. In January 2021, the TCB molecule was also involved in phase-II clinical trials focused on the treatment of Coronavirus Disease-19 caused by Severe Acute Respiratory Syndrome Coronavirus 2.

Chiral Aspects of Local Anesthetics.

Thanks to the progress made in chemical technology (particularly in the methodologies of stereoselective syntheses and analyses) along with regulatory measures, the number of new chiral drugs registered in the form of pure enantiomers has increased over the past decade. In addition, the pharmacological and pharmacokinetic properties of the individual enantiomers of already-introduced racemic drugs are being re-examined. The use of the pure enantiomer of a drug that has been used to date in the form of a racemate is called a "chiral switch". A re-examination of the properties of the pure enantiomers of racemates has taken place for local anesthetics, which represent a group of drugs which have long been used. Differences in (R) and (S)-enantiomers were found in terms of pharmacodynamic and pharmacokinetic activity as well as in toxicity. Levobupivacaine and robivacaine were introduced into practice as pure (S)-(-)-enantiomers, exhibiting more favorable properties than their (R)-(+)-stereoisomers or racemates. This overview focuses on the influence of chirality on the pharmacological and toxicological activity of local anesthetics as well as on individual HPLC and capillary electrophoresis (CE) methods used for enantioseparation and the pharmacokinetic study of individual local anesthetics with a chiral center.

Advances in the use of instrumental measurement of colour in the development, production and quality control of drugs, medicinal preparations and pharmaceutical auxiliary substances III.

Colour is an important indicator of the quality of pharmaceuticals, medicinal products and pharmaceutical excipients. The paper summarizes advances in the use of instrumental colour measurement in synthetic medicines and medicines of non-natural origin, their dosage forms and excipients published in 2013-2019.

Focus on perchlozone, an anti-tuberculosis drug from the Russian Federation.

The prevalence of multidrug-resistant tuberculosis (MDR--TB) and extensively drug-resistant tuberculosis (XDR--TB) has been increasing at an alarming rate worldwide. Todays “Fight against Tuberculosis“ programmes in the Russian Federation are subsidized by state and regional governments as well as health authorities. Each region has its own specific characteristics and needs specific interventions. Although some novel anti-tuberculosis (anti-TB) drugs (bedaquiline, delamanid) were approved by relevant authorities, and some promising compounds, especially those of oxazolidinones, are in various phases of clinical trials worldwide, the finding of effective, safe, pharmacokinetically favo-rable, economically and logistically accessible anti-TB agents still remains a serious challenge for medical and pharmaceutical sciences. Perchlozone, a compound containing a thiosemicarbazone scaffold, was approved in the Russian Federation in 2012 for the treatment (alone or as the active component of complex treatment regimens) of HIV-1 negative as well as HIV-1 positive patients suffering from MDR-TB or XDR-TB. Mechanism of anti-TB action of perchlozone might be similar to that of thiacetazone, which belongs into the same chemical class. Perchlozone has to be probably activated into reactive species by a mycobacterially encoded monoxygenase (EthA). The activated forms might act in multiple ways, including inhibition of mycobacterial cell wall synthesis due to interfence with a dehydration step of the type II fatty acid synthase pathway or sensitization of the Mycobacterium tuberculosis cell to oxidative stress. Favorable toxicological properties of perchlozone and its tolerability by the human organism were confirmed within revevant preclinical and clinical studies. However, recent preliminary investigations in vivo (animal models) could indicate genotoxicity after subacute inhalation of the drug. Regarding this issue, further development of more convenient nano- or microparticle-based formulations of perchlozone potentially improving targeted delivering and efficiency as well as decreasing (eliminating) its eventual toxicity might be taken into strong consideration.

Theory and practice of pharmacopoeial control of the quality of drugs and excipients VII. The colour reference solutions of the European pharmacopoeia (Ph. Eur.).

Data calculations of three different workplaces consistently show that the difference in colour ΔE (CIELAB) of some colour reference solutions according to Ph. Eur. with small colour and purified water are too small. As a result, there is failure with use of these solutions for visual assessment of the coloration of the liquids. Solving the problem in Ph. Eur. presupposes the introduction of instrumental colour evaluation into this pharmacopoeia. Key words: Ph. Eur. • colour reference solutions • colour difference • CIELAB • visual assessment • instrumental measurement.

Determination of Critical Micellar Concentration of Homologous 2-Alkoxyphenylcarbamoyloxyethyl-Morpholinium Chlorides.

The critical micellar concentrations of selected alkyloxy homologues of local anesthetic 4-(2-{[(2-alkoxyphenyl)carbamoyl]oxy}ethyl)morpholin-4-ium chloride with nc = 2, 4, 5, 6, 7, 8, and 9 carbons in alkyloxy tail were determined by absorption spectroscopy in the UV⁻vis spectral region with the use of a pyrene probe. Within the homologous series of the studied amphiphilic compounds, the ln(cmc) was observed to be dependent linearly on the number of carbon atoms nc in the hydrophobic tail: ln(cmc) = 0.705⁻0.966 nc. The Gibbs free energy, necessary for the transfer of the methylene group of the alkoxy chain from the water phase into the inner part of the micelle at the temperature of 25 °C and pH ≈ 4.5⁻5.0, was found to be −2.39 kJ/mol. The experimentally determined cmc values showed good correlations with the predicted values of the bulkiness of the alkoxy tail expressed as the molar volume of substituent R, as well as with the surface tension of the compounds.

Determination of dicoumarol in Melilotus officinalis L. by using molecularly imprinted polymer solid-phase extraction coupled with high performance liquid chromatography.

In this work, a method for the extraction of dicoumarol from plant sample utilizing selective adsorbent based on molecularly imprinted polymer was developed. Molecularly imprinted polymer (MIP) was synthesized by bulk polymerization, and on the surface of magnetic particles using dicoumarol as a template, methacrylic acid as functional monomer, chloroform as a porogen, and ethyleneglycol dimethacrylate as a cross-linker. Prepared polymeric materials were evaluated on the base of capacity, selectivity, and morphology. The maximal specific adsoption capacities of the sorbents were 45 µg (for bulk MIP) and 36 µg (for MIP on the magnetic particles) of dicoumarol per 1 g of polymer. An efficiencies of sorption processes of dicoumarol on prepared sorbents were evaluated under various conditions (type of sample solvent, pH, types of washing and elution solvents). The MIP based sorbents were used for solid phase extraction of dicoumarol. Applicability of MIP-SPE coupled to HPLC-DAD was tested for the selective extraction of dicoumarol from sample of sweet clover. The method was linear over concentration range from 1 to 100 µg mL-1 (the correlation coefficient 0.9984) with limit of detection 0.2 µg mL-1. Accuracy of the method was assessed for spiked sample at three concentration levels and recovery values were higher than 84% with relative standard deviation lower than 3.2%.

[Separation of phenylalanine and methionine enantiomers by HPLC method: a comparison of stationary phase types]. / Separácia enantiomérov fenylalanínu a metionínu metódou HPLC: porovnanie typov stacionárnych fáz.

The paper deals with enantioselective separation of amino acids by the high performance liquid chromatography method. Separations of enantiomeric forms were tested on the chiral stationary phases based on ß-cyclodextrine, isopropyl carbamate cyclofructan 6, and the macrocyclic antibiotic teicoplanin. The best enantioseparation was obtained on the teicoplanin-based chiral stationary phase in the reversed-phase mode. UV spectrophotometric detection at 210 nm was used for detection of amino acids. The method was validated with respect to linearity, precision, limit of detection, limit of quantitation, and recovery. Limits of quantitation for phenylalanine and methionine enantiomers were 0.3 and 0.2 µg.ml-1, respectively. The HPLC method with teicoplanin-based chiral stationary phase was applied for analysis of dietary supplements.Key words: separation of enantiomers HPLC phenylalanine methionine.

[Determination of flavonoids in natural materials with HPLC]. / Stanovenie flavonoidov v prírodnom materiáli metódou HPLC.

The paper reviews recent developments in the determination of flavonoids with HPLC. Flavonoids are a group of polyphenolic compounds commonly found in plants. Sample preparation is a very important step in the analytical procedure. The basic concept of a sample preparation method is to convert a real matrix into a sample in a format that is suitable for analysis by separation or analytical technique. In the present paper, attention was focused on the applications of molecularly imprinted polymers, especially on their utilization as selective sorbents in solid-phase extraction in the determination of flavonoids.

[Study of local anaesthetics: Part 206* Micellization of selected of quaternary ammonium salt derived from heptacaine]. / Stúdium lokálnych anestetík: Cast 206* Micelizácie vybraných kvartérnych amóniových solí odvodených od heptakaínu.

Micellization of selected quaternary ammonium compounds derived from heptacaine have been studied by absorption spectroscopy in the UV/VIS spectral region with the use of a pyrene probe. The compounds studied in the aqueous solution have been marked as H22, H26, H27, H29, H34, H + Al and H + B and the derivative marked as H34 was studied in a 3 mol/l ethanol solution at the temperature of 25 °C. In the homologous series of the studied bromides H22, H26, H27 and H29, cmc was observed to be dependent on the number of carbon atoms nc in the hydrophobic chain: ln (cmc) = -3.131-0.421nC. The Free Gibbs energy necessary for the transfer of a methyl group of the alkyl chain from the water phase to the inner part of the micelle at the temperature of 25 °C is (-0.421 ± 0.034)RT.

[Studies of local anaesthetics: part 205* studies of stability of heptacainium chloride and carbisocainium chloride using an accelerated non-isothermal test]. / Stúdium lokálnych anestetík: Cast 205* Stúdium stability heptakaíniumchloridu a karbizokaíniumchloridu zrýchleným neizotermickým testom.

The paper studies the kinetics of alkaline hydrolysis and stability under non-isothermal conditions of heptacainium chloride and carbisocainium chloride in the medium of aqueous-ethanolic solution of sodium hydroxide c = 0.1 mol/l and buffer solutions of values of pH 7.0 and pH 8.0. The results of the study of the kinetics of hydrolysis by means of a non-isothermal test - rate constants and activation energy values served as the basis for exact evaluation of the stability of these potential pharmaceuticals. The objective of the paper links up with the previous studies of these substances.

[Advances in the use of instrumental measurement of colour in the development, production and quality control of drugs, medicinal preparations and pharmaceutical auxiliary substances II*]. / Pokroky ve vyuzití instrumentálního merení barevnosti ve vývoji, výrobe a v kontrole jakosti léciv, lécivých prípravku a farmaceutických pomocných látek II*

The paper summarizes the use of instrumental colour measurement in the field of pharmaceuticals of natural origin and other substances of natural origin beneficial for health in recent 10 years. Colour measurement in this field was most frequently employed in the monitoring of various aspects of the process of drying of medicinal plants and their parts.

[Formulation of benzethonium chloride into gels]. / Formulácia benzetóniumchloridu do gélov.

This study is focused on the preparation of gels with antimicrobial effects. A quaternary ammonium salt, benzethonium chloride, in a concentration of 0.01-0.5% (w/w) was employed as the drug. The humectant employed was propylene glycol in concentrations of 5% and 10% (w/w). Two types of polymers, chitosan and hydroxyethyl cellulose, in the same concentrations of 2.5% (w/w), were used for gel preparation. Finally the flow properties, rheological parameters and pH values of the gels were evaluated. Based on the obtained results, the samples of the gels prepared on the basis of chitosan and hydroxyethyl cellulose, which have the following optimum composition shown below, were found: 2,5% (w/w) CHIT + 0,5% (w/w) BZCl + 10% (w/w) PG; 2,5% (w/w) HEC + 0,5% (w/w) BZCl + 5% (w/w) PG.