TEM study of boron phosphide: Discovery of rhombohedral BP

Microstructure of sphalerite (3C) boron phosphide, BP, produced by self-propagated high-temperature synthesis has been studied by high-resolution transmission electron microscopy. Along with numerous twins on the {111}3C plane, layers of wurtzite (2H) polymorphic modification and previously unknown for BP rhombohedral (3R) structure were found which indicates trimorphism of BP.

Study of the physicochemical properties of the etravirine substance

Introduction. Etravirine, being one of the most popular antiretroviral drugs, doesn't have its physicochemical properties sufficiently described in scientific publications. Detailed information on the substance properties is necessary both for organizing the synthesis and for justifying the dosage form and technology for its production, as well as for identifying bottlenecks and critical parameters that affect the quality of the finished product.Aim. Study the etravirine physicochemical properties to model the design of studies to create an innovative dosage formMaterials and methods. Etravirine (MSN Life Sciences Pvt. Ltd., Hetero Labs Ltd.). The melting point was determined by the capillary method. Etravirine samples were studied via differential scanning calorimetry (DSC), X-ray powder diffractometry, IR and NMR spectroscopy. Particle size was determined using laser diffraction analysis. The shape and size of the crystals were determined with the help of transmission electron microscopy (TEM). The concentration of etravirine in aqueous media was determined using the HPLC method with a fluorescence detector. The concentration of etravirine in organic solvents was determined spectrophotometrically.Results and discussion. The X-ray powder diffractometry and IR spectroscopy helped to determine the fact that the studied substances represent the same polymorphic modification. The melting point of etravirine ranges from 259 to 263 °C. Melting is accompanied by decomposition. The substance is practically insoluble in aqueous media at pH values in the range from 1.2 to 6.8, soluble in some organic solvents, readily soluble in dimethyl sulfoxide, tetrahydrofuran, dimethylformamide, dimethylacetamide. The distribution coefficient in the "1-octanol/phosphate buffer solution pH 6.8" solvent system was 5.22. The experiment showed that the etravirine substance is lipophilic. Etravirine is found to be a highly crystalline substance and represents needle-shape prismatic crystals.Conclusion. Etravirine is a lipophilic substance, practically insoluble in aqueous solutions, soluble in a number of organic solvents. The studied substances turned out to be the same polymorphic modification. Since the melting of the substance is accompanied by decomposition, high temperatures processes should be avoided.Conflict of interest. The authors declare that they have no obvious and potential conflicts of interest related to the publication of this article.

Polymorphism control of active pharmaceutical ingredients

Рolymorphism is receiving increasing attention due to its influence on the physicochemical and pharmacological properties of the active pharmaceutical ingredients (API) while maintaining the molecular structure. This review is devoted to the problem of APIs phase state control both at the development stage and during the circulation of the drug. The term «polymorphism» has different definitions depending on the branch of science. There is no unambiguous solution to this issue in the regulatory documentation of pharmaceutical industry either. Based on the analysis of literary sources, the article presents a comparison of pharmacopeia methods, recommended in Russian and foreign regulatory documents for the analysis of polymorphism of medicinal substances, including state pharmacopeias of Russia, Belarus, Kazakhstan, the USA, and Japan, as well as international pharmacopeias of the European Economic Union and the Eurasian Economic Union. The trend on using a complex of high-tech equipment is revealed. A systematic approach to analysis based on X-ray diffraction, thermal, spectral, microscopic, biological, and physical methods for determining constants makes it possible not only to identify the polymorphic modification of API, but also to characterize its structure, morphology, physicochemical properties and pharmacological activity. In the Russian Federation, the phenomenon of polymorphism is being studied especially intensively, and some control methods, such as biological methods, are validated only in Russian pharmacopeia. A promising direction for further research is the improvement and harmonization of regulatory documentation within the framework of this chemical and technological field of pharmacy. A global approach will help to reduce not only the probability of poor-quality products entering the market, but also the costs of establishing the authenticity of the active pharmaceutical ingredient produced.

Investigation of anti-inflammatory and antipyretic activity of polymorphic modification of n-(trifluoromethylphenyl)-4-hydroxy-2,2-dioxo-1h-2λ6,1-benzothiazine-3-carboxamide derivative in rats

Annotation. Polymorphism among biologically active substances is an extremely important factor that modifies the therapeutic properties of pharmaceutical substances and dosage forms, significantly affects the parameters of their biological activity and pharmacokinetics. Chemical synthesis among the derivatives of 4-R-2,2-dioxo-1H-2λ6,1-benzothiazine-3-carboxylic acids gave the leader compound N-(4-trifluoromethylphenyl)-4-hydroxy-2,2-dioxo-1H-2λ6,1-benzothiazine-3-carboxamide, the crystalline polymorph of which in the form of plates has a pronounced analgesic activity. The aim of the study was to investigate the anti-inflammatory activity of compound B by its effect on various components of the inflammatory reaction, as well as the antipyretic effect of this compound in rats. The anti-alterative activity was determined on the model of planar skin wounds, the antiproliferative effect - on the model of cotton granuloma, the anti-exudative effect - on the model of toxic pulmonary edema in rats. The antipyretic effect was studied in a model of milk fever in rats. The study was performed on 91 white male Wistar rats. Statistical processing of the obtained results was performed using the program "STATISTICA 6.1" by methods of variation statistics using parametric and nonparametric methods. The results showed that the polymorphic compound B has anti-inflammatory activity on all components of the inflammatory reaction - alteration, exudation and proliferation. In terms of efficacy in the model of experimental inflammation, this substance is superior to meloxicam, as its ED50 when administered orally is 5.2 mg/kg, while the reference drug - 9.1 mg/kg. Compound B exhibits a pronounced antipyretic effect in a rat fever model. Therefore, the polymorphic modification of the carboxamide derivative in the form of plates is promising for further research in order to create on its basis a drug with analgesic, anti-inflammatory and antipyretic properties.

Structural and Proton Conductivity Studies of Fibrous π-Ti2O(PO4)2·2H2O: Application in Chitosan-Based Composite Membranes

Although the fibrous polymorphic modification of titanium phosphate, π-Ti2O(PO4)2·2H2O (π-TiP) is known for decades, its crystal structure has remained unsolved. Herewith we report the crystal structure of π-TiP at a...

Human cholinesterases

The work is devoted to modeling the elementary stages of the hydrolysis reaction in the active site of enzymes belonging to the class of cholinesterases — acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). The study allowed to describe at the molecular level the effect of the polymorphic modification of BChE, causing serious physiolog ical consequences. Cholinesterase plays a crucial role in the human body. AChE is one of the key enzymes of the central nervous system, and BChE performs protective functions in the body. According to the results of calculations using the combined method of quantum and molecular mechanics (KM/MM), the mechanism of the hydrolysis of the native acetylcholine substrate in the AChE active center was detailed. For a series of ester substrates, a method for estimation of dependence of the enzyme reactivity on the structure of the substrate has been developed. The mechanism of hydrolysis of the muscle relaxant of succininylcholine BChE and the effect of the Asp70Gly polymorph on it were studied. Using various computer simulation methods, the stability of the enzyme-substrate complex of two enzyme variants with succinylcholine was studied.

Human cholinesterases

The work is devoted to modeling the elementary stages of the hydrolysis reaction in the active site of enzymes belonging to the class of cholinesterases — acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). The study allowed to describe at the molecular level the effect of the polymorphic modification of BChE, causing serious physiolog ical consequences. Cholinesterase plays a crucial role in the human body. AChE is one of the key enzymes of the central nervous system, and BChE performs protective functions in the body. According to the results of calculations using the combined method of quantum and molecular mechanics (KM/MM), the mechanism of the hydrolysis of the native acetylcholine substrate in the AChE active center was detailed. For a series of ester substrates, a method for estimation of dependence of the enzyme reactivity on the structure of the substrate has been developed. The mechanism of hydrolysis of the muscle relaxant of succininylcholine BChE and the effect of the Asp70Gly polymorph on it were studied. Using various computer simulation methods, the stability of the enzyme-substrate complex of two enzyme variants with succinylcholine was studied.

Особенности импульсного перемагничивания высококоэрцитивного материала на основе наночастиц ε-Fe-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-

The magnetic structure of the polymorphic modification of iron oxide ε-Fe2O3 is collinear ferrimagnetic in the range from room temperature to ~ 150 K. Further, with decreasing a temperature in ε-Fe2O3, a magnetic transition occurs, accompanied by a significant decrease in the coercive force HC, and in the low temperature range ε-Fe2O3 is characterized by a complex incommensurate magnetic structure. In this work, we experimentally investigated the processes of dynamic magnetization reversal of ε-Fe2O3 nanoparticles of an average size of 8 nm in the temperature range of 80–300 K, comprising various types of magnetic structure of this iron oxide. A bulk material was studied - xerogel SiO2 with ε Fe2O3 nanoparticles embedded in pores. To measure the magnetic hysteresis loops under dynamic magnetization reversal, a pulsed magnetic field technique of Hmax up to 130 kOe was used, using the method of discharging a capacitor bank through a solenoid. The coercive force of HC during dynamic magnetization reversal noticeably exceeds HC for quasi-static conditions. This is caused by processes of superparamagnetic relaxation of the magnetic moments of particles during pulsed magnetization reversal. In the range from room temperature to ~ 150 K, the rate of change of the external field dH / dt is the main parameter determining the behavior of the coercive force under the conditions of dynamic magnetization reversal. This behavior is expected for a system of single-domain ferro- and ferrimagnetic particles. Under external conditions (at a temperature of 80 K), when the magnetic structure of ε Fe2O3 is incommensurate, the coercive force during pulsed magnetization reversal already depends on the parameter dH / dt, and is largely determined by the maximum applied field Hmax. Such a behavior, atypical for systems of ferrimagnetic particles, is already caused by dynamic spin processes inside ε-Fe2O3 particles during fast magnetization reversal.