Journal of Organic and Pharmaceutical Chemistry

Aim. To study the qualitative composition, the quantitative content of catechins in green tea leaves and compare the data obtained with those evaluated by spectrophotometry.
Materials and methods. Green tea leaves used for the analysis were collected in Anhui Province, China. The extract for the HPLC analysis was obtained by the maceration method with 60 % ethanol twice in the raw material/extractant ratio of 1 : 20. In the case of the spectrophotometric analysis, green tea leaves were extracted with 70 % ethanol twice by the maceration method in the raw material/extractant ratio of 1 : 20. The analysis of the extract from green tea leaves was performed by high performance liquid chromatography using a Prominence LC-20 Shimadzu chromatographic system (Japan) with a SPD-20AV spectrophotometric detector, an Agilent Technologies Microsorb-MV-150 column (reversed phase, C18 modified silica gel, length – 150 mm, diameter – 4.6 mm, particles size – 5 μm). Substances in the extract were identified by comparing the retention time and the spectral characteristics of the test substances with the same characteristics of the reference standards. Spectrophotometric measurements were carried out using a UV-1000 single beam spectrophotometer (China) with the pair of S90-309Q quartz square cells.
Results and discussion. Using high performance liquid chromatography 5 catechins were identified.
Among them epigallocatechin-3-O-gallate (10.85 %) predominated, while catechin (0.61 %) had the lowest concentration. The total amount of catechins in green tea leaves was 30.56 and 24.79 % by HPLC and spectrophotometry, respectively. The F- and t-tests showed that there was no significant difference between the results of HPLC and spectrophotometry.
Conclusions. The qualitative composition and the quantitative content of catechins have been determined in the extract from green tea leaves by high performance liquid chromatography and spectrophotometry. Both HPLC and spectrophotometric methods can be used to determine the total catechin content in green tea leaves. The high content of catechins makes the extract promising for further study and creation of new herbal medicinal products and dietary supplements. The results obtained will be used for standardization of green tea leaves and for future pharmacological research of its extract.

Prospects for the search of antiviral agents among 4-thiazolidinone derivatives, as well as the optimal directions of the main core structure optimization – namely C5 and N3, have been described. As the result of the screening performed (within the Antimicrobial Acquisition and Coordinating Facility programme), the values of the antiviral activity of the target 5-substituted-4-thiazolidinones with the carboxylic group (or its derivatives) in the N3 residue on relation to a wide range of the viral panels have been determined. The active compounds, which can be regarded as promising structures in the anti-flu agent design, have been identified, as well as 3-{5-[2-chloro-3-(4-nitrophenyl)-allylidene]-4-oxo-2-thioxothiazolidine-3-yl}-propionic (1) and –succinic acids (3) have been identified has hit-compounds with a marked anti-VZV activity (SI values – 27 and 38, respectively).

The search for new groups of anti-inflammatory and analgesic drugs is a topical issue of the current medicinal chemistry. It is caused by numerous diseases that are accompanied by pain and inflammation, as well as by imperfection of the existing drugs aimed to provide treatment of these pathological conditions. Derivatives of 1H-2,1-benzothiazin-4(3H)-one 2,2-dioxide are promising chemicals to search and develop drugs with the pharmacological properties required. This heterocyclic system is structurally close to 2H-1,2-benzothiazin-4-one 1,1-dioxide, which is the core of the famous non-steroidal anti-inflammatory drugs related to the “oxicam” group. Moreover, derivatives of 1H-2,1-benzothiazin-4(3H)-one 2,2-dioxide are also considered to be promising structures for searching effective antimicrobial substances among them. The present article is devoted to the synthesis of new derivatives of 1H-2,1-benzothiazin-4(3H)-one 2,2-dioxide, namely ethyl 2-amino-4-alkyl-4,6-dihydropyrano[3,2-c][2,1]benzothiazin-3-carboxylate 5,5-dioxides and triethylammonium 3-[(4-hydroxy-1-ethyl-2,2-dioxido-1H-2,1-benzothiazin-3-yl)alkyl]-1-ethyl-1H-2,1-benzothiazin-5-olat 2,2-dioxides. Condensed 2-amino-4-alkyl-4H-pyran-3-carboxylates were synthesized via the three-component one-pot interaction of 1-ethyl-1H-2,1-benzothiazin-4(3H)-one 2,2-dioxide with ethyl cyanoacetate and aliphatic aldehydes. The abovementioned triethylammonium salts were obtained by the two component interaction of 1-ethyl-1H-2,1-benzothiazin-4(3H)-one 2,2-dioxide with aliphatic aldehydes in the presence of the equimolar amount of triethylamine. The study of the anti-inflammatory and analgesic activity has demonstrated high prospects of new effective drugs when searching among two classes of the compounds synthesized. The screening of the antimicrobial activity has shown that the compounds synthesized are the most active against the fungal strain of C. albicans.

Much attention is currently paid to the study of the antioxidant properties of various objects – individual antioxidants, dietary supplements, medicines, liquid plant extracts. Antioxidant medicines are widely used as the main or additional correction agents in the treatment of a number of diseases. Therefore, the study and development of procedures for determining the antioxidant activity is a prospective task for today.

Aim. To determine the contribution of different concentrations of ethanol to the level of the antioxidant activity (AOA) of ascorbic acid solutions by the potentiometric method.

Results and discussion. The different ethanol content in the solution had the following percent of the contribution to the value of AOA of ascorbic acid solutions – 1.85, 3.56, 4.89, 6.76, 7.63 % for 20, 40, 60, 80, 96 % ethanol, respectively. The linearity of the procedure was proven in the range from 0.039 to 0.31 mmol/L.

Experimental part. The object of the study was solutions of ascorbic acid prepared using ethanol of different concentrations – 20, 40, 60, 80, 96 %. Potentiometric measurements were conducted by a Hanna 2550 pH meter (Germany) with an EZDO 5010 combined platinum electrode. Weighing was carried out using an АN100 digital analytical balance (AXIS, Ukraine) with d = 0.0001 g. Ascorbic acid was purchased from Sigma Aldrich (≥ 99.0 %), K₃[Fe(CN)₆], K₄[Fe(CN)₆], NaHPO₄, KH₂PO₄ were of analytical grade.

Conclusions. It has been found that ethyl alcohol affects the change of the potential in the electrochemical cell and the level of AOA of ascorbic acid solutions. The percentage of the contribution of different concentrations of ethyl alcohol to the AOA value ranges from 1.85 to 7.63 %. The approach and the formula for calculation that take into account the effect of ethyl alcohol on the final AOA result of the test sample of ascorbic acid in a water-alcohol solutions have been proposed. The results of this study can be used in the pharmaceutical and food industries to determine, assess and control the AOA level of dietary supplements, liquid extracts, tinctures, medicines, and alcoholic beverages.

Species of Iris genus (Iridaceae) have a long history of traditional medicinal use in different countries as alternative aperient, tonic, cathartic, diuretic, gall bladder diseases, liver complaints, dropsy, purification of blood, venereal infections, fever, bilious infections and for a variety of heart diseases. The rhizomes of Iris are the rich source of the secondary metabolites, in which flavonoids predominate. The clinical studies of substances from irises gave positive results in the treatment of cancer, bacterial and viral infections. Continuing the search of new biologically active compounds from the plants of Iridaceae family for the first time three isoflavones that are new for this species – irigenin, iristectorigenin B and its glucoside iristectorin B have been isolated from the ethanolic extract of the rhizomes of Iris hungarica Waldst. et Kit., which is widespread in Ukraine. The structure of the compounds is described as 5,7,3’-trihydroxy-6,4’,5’-trimethoxyisoflavone, 5,7,4’-trihydroxy-6,3’-dimethoxyisoflavone and iristectorigenin B-7-O-β-D-glucoside, respectively. The compounds were obtained from the ethyl acetate fraction of the iris rhizomes by column chromatography on silica gel with sequential elution of the chloroform – ethanol solvent with different concentrations. The structure of the compounds has been determined by chemical and spectral methods and in comparison with the literature data.

Aim. To develop a new approach to the design of (1,3-thiazolidin-2-ylidene)ketones and expansion of their synthetic potential as convenient building blocks in the reactions of [3+2]- and [3+3]-cyclization.

Results and discussion. Еlectrophilic intramolecular cyclization (EIC) of N-allythioamides of β-ketoacids using phosphoric acid or iodine is a convenient synthetic method to obtain new (5-methyl- and 5-iodomethyl-1,3-thiazolidine-2-ylidene)ketones. Cyclization of ketones with maleic anhydride leads to derivatives of 2,3-dihydropyrrolo[2,1-b][1,3]thiazole. [3+3]-Cyclocondensation with methyl propiolate and dimethyl acetylenedicarboxylate results in formation of the functionalized [1,3]thiazolo[3,2-a]pyridine derivatives.

Experimental part. (5-Methyl- and 5-iodomethyl-1,3-thiazolidin-2-ylidene)ketones were synthesized from N-allylthioamides using phosphoric acid or iodine in chloroform. (1,3-Thiazolidin-2-ylidene)ketones react with maleic anhydride, methyl acetylenecarboxylate or dimethyl acetylenedicarboxylate resulting in a 2,3-dihydropyrrolo[2,1-b][1,3]thiazole-5(6H)-one and 2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyridine derivatives.

Conclusions. A convenient method of [5-methyl- and 5-iodomethyl-1,3-thiazolidin-2-ylidene]ketones preparation based on the EIC of N-allylthioamides of β-ketoacids has been developed using phosphoric acid and iodine. The (1,3-thiazolidin-2-ylidene)ketones synthesized can be useful in cyclization reactions leading to functional pyrrolo[2,1-b][1,3]thiazole and [1,3]thiazolo[3,2-a]pyridine derivatives.

A suitable and effective scheme for the synthesis of 2-hydrazinoquinazolin-4-ones has been suggested and tested. It can provide a wide chemical diversity of the final products. The scheme developed starts from esters of 2-isothiocyanobenzoic acids, which easily form 3-substituted 2-thioxoquinazolin-4-ones with a high yield in the reaction with primary amines. When refluxing the latter in a heterogenic emulsion of dioxane and hydrazine hydrate the nucleophilic substitution of the sulfur atom occurs with 3-substituted 2-hydrazinoquinazolin-4-ones formation accumulated in the dioxane phase. After separation of the dioxane layer and dilution with water the precipitate of sufficiently pure target 2-hydrazinoquinazolin-4-ones is formed. Under these conductions there is no splitting of the amide group, which can be a part of substituents. But in case of amides of (4-oxo-2-thioxo-1,4-dihydroquinazolin-3(2H)-yl)acetic acid after inserting of the hydrazine substituent the cyclization occurs as a result of the intramolecular substitution of the amine residue of the amide fragment with formation of 2H-[1,2,4] triazino[3,4-b]quinazoline-3,6(1H,4H)-dione. The structure of the compounds synthesized has been proven by elemental analysis and 1H NMR spectroscopy data. The compounds obtained are promising synthones for construction of diversified heterocyclic systems, which can be of interest as potential pharmacological substances.

Calix[4]arene are known to be a promising scaffold for designing inhibitors of protein tyrosine phosphatases.
In this work calix[4]arene mono- and bis-α-hydroxymethylphosphonic acids have been tested in vitro for the inhibitory activity against some therapeutically important protein tyrosine phosphatases. The results obtained have shown that these macrocyclic compounds can inhibit CD45, PTP1B, and SHP2 with IC50 values in the micromolar range. At the same time the inhibitors have demonstrated lower activity toward other protein tyrosine phosphatases such as TC-PTP and PTPβ. It has been found that mono-substituted calix[4]arene is more potent inhibitor of CD45 than the bis-substituted one and shows about 2-15 fold selectivity over TC-PTP, PTPβ, SHP2 and PTP1B. Model 4-hydroxyphenyl-α-hydroxymethylphosphonate displays at least one order lower activity than the phosphonate derivatives of calix[4]arene. Thus, the combination of a macrocyclic platform and α-hydroxymethylphosphonate group is essential for the inhibition activities of these compounds. Computer-simulated docking studies have been performed using AutoDock 4.2 programme by the example of PTP1B. The data obtained indicate that the inhibitors can bind in the active site of the enzyme. To clarify the inhibition mechanism the possible enzyme-inhibitor complexes have been considered using several crystal structures of PTP1B and all stereoisomeric forms of the inhibitors.

Aim. To determine the parameters of standardization of a dry extract from large cranberry (Oxycoccus macrocarpus (Ait.)) leaves and a dry extract modified with arginine and develop projects of Drug Quality Control Methods (DQCM) for these substances.
Materials and methods. The study object was dry extracts from large cranberry leaves. Leaves were harvested in October 2021 in the Zhytomyr region (Kostivtsi village, 50.326862437345945, 29.54310845594284). The extracts were obtained with a 50 % solution of ethyl alcohol in the ratio of 1:30 by double maceration. Half of the combined extract was dried to a dry extract (Extract 1), and the other half was modified with arginine in the threefold equimolar amount relative to the total amount of phenolic compounds and evaporated to a dry extract (Extract 2). Standard pharmacopoeial methods were used to determine standardization parameters. The quantitative determination was carried out using the spectrophotometric method by the content of flavonoids calculated with reference to hyperoside and hydroxycinnamic acids calculated with reference to chlorogenic acid on an Evolution 60S spectrophotometer (Thermo Scientific Spectronic, USA).
Results and discussion. The parameters of standardization of dry extracts from large cranberry leaves were determined. The project of DQCM was proposed according to the following indicators: description, solubility, identification using the thin-layer chromatography method (by the content of flavonoids, hydroxycinnic acids and arginine), loss on drying, the residual amount of organic solvents (ethanol), microbiological purity, and the content of heavy metals. The assay was carried out using spectrophotometry by the content of flavonoids and derivatives of hydroxycinnic acids. Three batches of the extracts obtained, which fully corresponded to the projects of DQCM developed, were analyzed.
Conclusions. The parameters of standardization of dry extracts from large cranberry leaves have been determined, and projects of DQCM for the substances obtained have been developed. It is the basis for creating new medicines for the correction of insulin-resistant conditions in Type 2 diabetes mellitus.

The synthesis of new N, N`-disubtituted 5-spiro-2,4,6-trihydropyrimidinetriones by ring-closing metathesis reactions has been presented in this work. Starting compounds for obtaining of spirocycles (5,5-diallyl-1,1-dioxythiolanyl-2,4,6-trihydropyrimidinetriones) have been synthesized by two pathways, one of them is condensation of carbamides with malonic acid in the presence of dehydrating agents, whereas the other path consists in the condensation of dicyanodiamide with diallylcyanoacetic ester in the presence of sodium alkoxide, and the resulting products are subjected to alkylation with the following acid hydrolysis. It has been found that imidazolidine containing the isopropoxybenzylidene ruthenium complex is the most suitable for carrying out of ring-closing metathesis reactions since it has the high thermal stability; it allows to obtain the target products with a high yield due to carrying out these reactions at the higher temperatures. The preliminary computer prognosis of the biological activity of new 1,1-dioxythiolan derivatives with the help of PASS (Prediction of Activity Spectra for Substances) programme has shown that some of these compounds can be ATPase proteasome inhibitors. Moreover, new spirocyclopenten containing derivatives may be promissing as precursors for obtaining of biologically active substances.

Precarbene and metalcarbene compounds of a series of imidazole have been synthesized to study their antimicrobial activity. Calix[4]arene imidazolium salts 3,4a,b have been obtained from the corresponding chloromethyl derivatives of calix[4]arenes and N-substituted imidazoles in dimethylformamide or tetrahydrofuran, and salt 5 – from p-xylylenediimidazoles and 1-bromoadamantane in o-dichlorobenzene. Monocarbene complexes of palladium 8a-c, copper(I) 8d and biscarbene complexes of nickel 9a and cobalt 9b have been synthesized by the direct interaction of stable carbenes with transition metal salts or by the analogous reactions in situ in tetrahydrofuran. The NMR spectra data of the compounds synthesized are given. The most characteristic signals of the carbenoid carbon atoms are detected in the 13С NMR spectra of complexes 8a-d, 9a in the range of 165-178 ppm. A high antimicrobial activity has been found for carbenoid salts 4a,b, 5 on the test-culture of M. Luteum. It corresponds to the minimal bacteriostatic concentration (MBsC) of 15.6 mkg/mL and the minimal bactericidal concentration (MBcC) of 62.5 mkg/mL for compound 2. The higher activity has been found for carbene complexes of nickel 9a and cobalt 9b on the test-culture of M. luteum (MBsC is 7.8 mkg/mL and MBcC is 15.6 mkg/mL), and the highest 9b on the test-cultures of M. luteum and C. tenuis (the minimal fungistatic concentration is 1.9 mkg/mL and the minimal fungicidal concentration is 3.9 mkg/mL).

 Organic acids are a large group of biologically active compounds that perform important functions in the plant organism. Moreover, all plants, regardless of the species and family, contain organic acids to a small or large extent as organic acids belong to intermediate metabolites arising from the oxidation of proteins and amino acids, fats and carbohydrates.
Aim. To validate the method of alkalimetry proposed with potentiometric detection of the end-point for the quantitative determination of free organic acids in raspberry leaves.
Results and discussion. The method proposed was validated according to the International Conference on Harmonization (ICH) guidelines. The linearity was in the concentration range of 40 – 200 % (r² = 0.9991). The percentage of recovery was found to be in the range of 98.77 – 102.48 %. The repeatability and intermediate precision were 1.58 % and 1.74 %, respectively. The method is accurate and reliable, with the relative standard deviation of less than 2 %.
Experimental part. Leaves of raspberry were collected in the Kharkiv region during the period of full ripening. A Hanna 2550 pH-meter with a HI 1131P potentiometric electrode was used for alkalimetric titration of free organic acids. The titration was carried out using a microburette with Class A accuracy.
Conclusions. The alkalimetry method for the quantitative determination of free organic acids in raspberry leaves has been proposed and validated according to the following parameters: specifcity, linearity, accuracy, repeatability, intermediate precision, robustness. It has been confrmed that the method is simple, reliable, accurate and cost-effective.
Key words: raspberry; leaves; free organic acids; alkalimetry; validation

Aim. To study the qualitative composition, the quantitative content of catechins in green tea leaves and compare the data obtained with those evaluated by spectrophotometry.
Materials and methods. Green tea leaves used for the analysis were collected in Anhui Province, China. The extract for the HPLC analysis was obtained by the maceration method with 60 % ethanol twice in the raw material/extractant ratio of 1 : 20. In the case of the spectrophotometric analysis, green tea leaves were extracted with 70 % ethanol twice by the maceration method in the raw material/extractant ratio of 1 : 20. The analysis of the extract from green tea leaves was performed by high performance liquid chromatography using a Prominence LC-20 Shimadzu chromatographic system (Japan) with a SPD-20AV spectrophotometric detector, an Agilent Technologies Microsorb-MV-150 column (reversed phase, C18 modified silica gel, length – 150 mm, diameter – 4.6 mm, particles size – 5 μm). Substances in the extract were identified by comparing the retention time and the spectral characteristics of the test substances with the same characteristics of the reference standards. Spectrophotometric measurements were carried out using a UV-1000 single beam spectrophotometer (China) with the pair of S90-309Q quartz square cells.
Results and discussion. Using high performance liquid chromatography 5 catechins were identified.
Among them epigallocatechin-3-O-gallate (10.85 %) predominated, while catechin (0.61 %) had the lowest concentration. The total amount of catechins in green tea leaves was 30.56 and 24.79 % by HPLC and spectrophotometry, respectively. The F- and t-tests showed that there was no significant difference between the results of HPLC and spectrophotometry.
Conclusions. The qualitative composition and the quantitative content of catechins have been determined in the extract from green tea leaves by high performance liquid chromatography and spectrophotometry. Both HPLC and spectrophotometric methods can be used to determine the total catechin content in green tea leaves. The high content of catechins makes the extract promising for further study and creation of new herbal medicinal products and dietary supplements. The results obtained will be used for standardization of green tea leaves and for future pharmacological research of its extract.

Aim. To synthesize cyclobutane-derived amines and carboxylic acids bearing CH₂F or CHF₂ groups in the α position; to determine the regularities of the effect of fluoroalkyl substituents on the acid-base properties of the title compounds.
Results and discussion. Synthetic approaches to 1-(fluoromethyl)- and 1-(difluoromethyl)cyclobutanamines, 1-(fluoromethyl)- and 1-(difluoromethyl)cyclobutanecarboxylic acids have been developed. It has been found that the pKa (pK_a(H)) values measured for the title compounds, as well as for their non-substituted and CF₃-substituted analogues, are consistent with the electron-withdrawing effect of the corresponding fluoroalkyl substituents.
Experimental part. The synthesis of the title compounds commenced from the known ethyl 1-(hydroxymethyl)cyclobutanecarboxylate or the product of its Swern oxidation (the corresponding aldehyde) and included fluorination, alkaline ester hydrolysis (for carboxylic acids), and modified Curtius rearrangement (for amines). The pKa value was determined from the pre-equivalence point part of the titration curve using the standard acid-base titration.
Conclusions. A newly developed synthetic approach to 1-(fluoromethyl)- and 1-(difluoromethyl)cyclobutanamines, 1-(fluoromethyl)- and 1-(difluoromethyl)cyclobutanecarboxylic acids allows to obtain the title compounds in multigram quantities (up to 97 g). With a single exception, the acid-base properties of these products, as well as their parent non-substituted and CF₃-substituted analogues, change in a monotonous manner in accordance with inductive electronic effect of the fluorine atom(s).

Aim. To reveal the prospects of the search of novel medicinal substances based on the studies of the derivatives of thieno[2,3-d]pyrimidine with the carboxylic groups as the substituents in the pyrimidine ring using the analysis of the published literature data.

Results and discussion. The study has shown a wider range of the pharmacological activity of thieno[2,3-d]pyrimidine-2-carboxylic acid derivatives compared to thieno[2,3-d]pyrimidine-4-carboxylic acids, as well as their availability, despite the fact that the number of preparative methods for the synthesis of these substances is rather limited. The most popular method is cyclization of 2-aminothiophene-3-carboxylic acids with ethyl cyanoformate. On the other hand, thieno[2,3-d]pyrimidine-4-carboxylic acid derivatives are presented in even fewer studies and are poorly studied; many of them are difficult to be synthesized and practically are not found in the pharmacological patent literature.

Conclusions. The literature data analysis has revealed the small number of efficient synthetic methods suitable for preparation of thieno[2,3-d]pyrimidines with the carboxylic groups as the substituents in the pyrimidine ring, as well as their low availability for the pharmacological studies. It is also noteworthy that the derivatives of thieno[2,3-d]pyrimidine-4-carboxylic acids are even less studied than the related compounds of thieno[2,3-d]pyrimidine-2-carboxylic acid series, and therefore, more attention should be paid to them as the objects for experimental chemistry and pharmacology.

Received: 12.08.2020
Revised: 23.09.2020
Accepted: 08.10.2020

Aim. To study the reactivity of 2-methylquinolin-4(1H)-ones in the bromination reaction in order to develop target-oriented methods for the synthesis of compounds that can affect the Quorum sensing processes of various bacterial communities.

Results and discussion. Features of the reactivity of 2-methylquinoline-4(1H)-ones in the bromination reaction using two halogenating reagents – molecular bromine and N-bromosuccinimide (NBS) have been studied. It has been shown that in both cases the direction of halogenation depends on the presence and nature of the substituent in position C(3) of the heterocycle. It has been found that variations in reagents, solvents, and catalysts did not lead to changes in the qualitative composition of the reaction products and only slightly affected their yields.

Experimental part. The synthesis of bromo derivatives of quinoline-4(1H)-ones was carried out by acting on the initial compounds of a molecular bromine or NBS in glacial acetic acid or chloroform, respectively, in the presence of catalytic amounts of benzoyl peroxide or without it. The structure of the compounds synthesized was proven by the data of ¹H NMR spectroscopy and elemental analysis.

Conclusions. The features of the bromination reaction in the series of 3-substituted 2-methylquinolin-4(1H)-ones have been studied. It has been found that depending on the nature of the substituent in position C(3) of quinolone, bromination occurs on the methyl group of position C(2), or on positions C(3) and C(6) of the heterocycle. In the case of 3-benzyl-2-methylquinolin-4(1H)-one, bromination takes place on the methyl group of position C(2) of quinolone to form 3-benzyl-2-(bromomethyl)quinolin-4(1H)-one, which can be used for developing a new class of drugs designed to affect the virulence factors of microorganisms. The reactivity of 3-benzyl-2-(bromomethyl)-quinolin-4(1H)-one has been studied on the example of n-hexylamine alkylation.

Received: 10.07.2020
Revised: 29.10.2020
Accepted: 14.11.2020

1,2,3,4-Tetrahydroisoquinoline (THIQ) is a common scaffold of many alkaloids isolated from several plants and mammalian species. THIQ derivatives possess a broad spectrum of biological activities, including antitumor, antitubercular, antitrypanosomal, antibacterial, anti-HIV, anti-inflammatory, anti-Alzheimer, and anticonvulsant ones.
Aim. To cover updated studies on the biological properties of THIQ derivatives, as well as their structure-activity relationship (SAR), in order to highlight the effect of diverse functional groups responsible for the manifestation of the desired activity.
Results and discussion. We have presented the review on biological activities of THIQ. The SAR studies show that the electron-donating, electron-withdrawing and some heterocyclic functional groups on the backbone plays a vital role in modulating the biological potential of the compounds synthesized.
Conclusions. This review will help pharmaceutical researchers to synthesize novel and potent compounds containing THIQ scaffold.

Aim. To analyze and summarize the synthetic potential of 1,2,3-triazole-4(5)-amines as efficient building blocks in the synthesis of triazolo-annulated pyridine, azine and azepine systems.
Results and discussion. Original literature sources revealing the synthetic potential of 4(5)-amino functionalized 1,2,3-triazoles as convenient and available building blocks for the preparation of triazolo-annulated pyridines, azines and azepines were analyzed and systematized. Condensation of 1,2,3-triazole-4(5)-amines with methylene active compounds was shown to be a powerful tool for the synthesis of versatile triazolo[4,5-b]pyridines. In turn, the cyclocondensation based on 5-amino-1,2,3-triazole-4-carboxylic acids and their structurally modified derivatives was proven to be a general way for obtaining a number of triazolo[4,5-d]pyrimidine systems. Few representatives of triazolo-annulated pyridazines, 1,3-oxazines and 1,3-thiazines were synthesized by the intramolecular cyclization of the corresponding 4-aryl(carboxy-, aminomethyl)-5-amino-1,2,3-triazoles. The cyclocondensation involving 4,5-diamino-, 4-carbofunctionalized 5-amino-1,2,3-triazoles and 4-amino-5-thiocarboxamido-1,2,3-triazoles was successful for the construction of di-, oxa- and thiazepino-annulated triazoles.
Conclusions. The analysis, systematization and summary of the literature regarding the synthetic potential of 1,2,3-triazole-4(5)-amines conclusively demonstrate that these structures are easily available and convenient molecular blocks for the construction of triazolo-annulated pyridine, azine and azepine systems that are important for synthetic and biomedical research.

The analysis of model samples of the drug Aminazin has been performed, its active substance is chlorpromazine hydrochloride. These model solutions were subjected to sterilization with previous exposure at room temperature. It has been found that depending on duration of the exposure during sterilization the degradation of the drug occurs in two possible ways – with formation of opalescence or without it. The schemes of degradation with formation of either one product – chlorpromazine sulfoxide, or some products – chlorpromazine sulfoxide, chlorpromazine N-oxide, nor-chlorpromazine and others have been proposed. It has been found that opalescence of solutions is caused by formation of degradation products – chlorpromazine N-oxide and norchlorpromazine that are slightly soluble in water. The analysis of model samples was performed using the liquid chromatography/mass spectrometry methods developed by the authors. In the course of analysis the molecular weights corresponding to the abovementioned products were obtained. Therefore, the experimental confirmation of the chemes of degradation proposed has been obtained. As the result of the research conducted the chromatographic method for detection of impurities using liquid chromatography/mass spectrometry has been developed, and the main ways of degradation of chlorpromazine hydrochloride in aqueous solutions have been determined. According to the result of the research the recommendations to the manufacturing process have been developed, and measures for optimizing the composition of the drug have been proposed.

Aim. To generalize and systematize information on the properties of modern chemical disinfectants and antiseptic agents (DA and AA).
Results and discussion. The review provides generalized and systematized information on the properties of modern chemical DA and AA – alkylating reagents, aldehydes, amides, amidines, bisguanidines, dyes, halogenated reagents, halogens and their complexes, 2-nitrofuran derivatives. The classification of DA and AA by their chemical structure was carried out. The activity spectra, possible application ways and forms of DA and AA were given. Their toxicity and impact on the environment were described as well.
Conclusions. On the basis of the analysis carried out it was shown that aldehydes, halogen-active compounds and halogen-containing complexes are modern effective DA and AA with a wide spectrum of biocidal action. Amides, amidines and bisguanidines are characterized by a narrow spectrum of activity. Dyes and 2-nitrofuran derivatives are old-fashioned antiseptics.

Aim. To develop a convenient synthetic approach for the preparation of multigram amounts of 4-(trifluoromethoxy)-piperidine and 4-(trifluoromethoxymethyl)piperidine – promising building blocks for medicinal chemistry.
Results and discussion. 4-(Trifluoromethoxy)piperidine (8.4 g) and 4-(trifluoromethoxymethyl)piperidine (12.9 g) were synthesized in 5 stages starting from 4-hydroxypiperidine (the overall yield 40 %) and 4-(hydroxymethyl)piperidine (the overall yield 13.5 %), respectively.
Experimental part. The first stage of the synthetic strategy was acylation of 4-hydroxypiperidine with benzoyl chloride. N-benzoyl-4-hydroxypiperidine obtained was transformed to N-benzoyl-4-(trifluoromethoxy)piperidine in two stages using the Hiyama method (the synthesis of the corresponding S-methyl xanthate with the subsequent desulfurization/fluorination using N-bromosuccinimide and Olah’s reagent). Then the N-benzoyl group was reduced to benzyl one, which was removed using 1-chloroethyl chloroformate. The similar approach was applied to the synthesis of 4-(trifluoromethoxymethyl)piperidine starting from 4-(hydroxymethyl)piperidine. The structure and composition of the compounds synthesized were confrmed by ¹Н, ¹³C and ¹⁹F NMR spectroscopy,
mass-spectrometry and elemental analysis.
Conclusions. The synthetic approach developed is a convenient method for the multigram preparation of
4-(trifluoromethoxy)piperidine and 4-(trifluoromethoxymethyl)piperidine and can be used for the synthesis of other secondary amines containing the CF₃O-group.
Key words: fluorination; trifluoromethoxy group; xanthate; piperidine; protection group

Aim. To synthesize, study the antimicrobial activity and suggest antimicrobial activity mechanism for the
novel derivatives of 6-(1H-benzimidazol-2-yl)-5-methylthieno[2,3-d]pyrimidin-4(3H)-one.
Results and discussion. As the result of the targeted modification of 6-(1H-benzimidazol-2-yl)-5-methylthieno[2,3-d]-pyrimidin-4(3H)-one in position 3 with acetamide and 1,2,4-oxadiazol-5-ylmethyl substituents, the compounds, which demonstrated better antimicrobial activity in the agar well diffusion assay than the reference drug Streptomycin, were obtained. To elucidate the mechanism of action of the novel compounds, the docking studies were con-
ducted to the active site of the 16S subunit of ribosomal RNA, the proven target for aminoglycoside antibiotics, as well as tRNA (Guanine37-N¹)-methyltransferase (TrmD), which inhibitors were considered as a new potential class of antibiotics.
Experimental part. By the interaction of 6-(1H-benzimidazol-2-yl)-5-methylthieno[2,3-d]pyrimidin-4(3H)-one with a series of N-arylchloroacetamides and 3-aryl-5-(chloromethyl)-1,2,4-oxadiazoles in DMF in the presence of K₂CO₃ the target compounds were obtained. The antimicrobial activity was assessed by the agar well diffusion method. The concentration of microbial cells was determined by the McFarland standard; the value was 10⁷ cells in 1 mL of the media. The 18 – 24 hour culture of microorganisms was used for tests. For the bacteria cultivation,
Müller-Hinton agar was used, Sabouraud agar was applied for C. albicans cultivation. The compounds were tested as the DMSO solution with the concentration of 100 µg/mL; the volume of the solution was 0.3 mL, the same volume was used for Streptomycin (the concentration 30 µg/mL). The docking studies were performed using Autodock Vina. Crystallographic data for the complexes of Streptomycin with the 16S subunit of ribosomal RNA
(1NTB) and its active site, as well as for tRNA (Guanine37-N¹)-methyltransferase (EC 2.1.1.228; TrmD) (5ZHN) and its active site were obtained from the Protein Data Bank.
Conclusions. It has been determined that 2-[6-(1H-benzimidazol-2-yl)-5-methyl-4-oxothieno[2,3-d]pyrimidin-3(4H)-yl]-N-[4-(ethoxy)phenyl]acetamide, which is the most active as an antimicrobial agent among the compounds tested, also shows the best binding activity towards the active site of tRNA (guanine37-N¹)-methyltransferase.

Aim. To develop the unified method of the HPLC analysis of loratadine, which can allow obtaining reliable and reproducible results of the studies of pharmaceuticals and biological matrices for monitoring the treatment effectiveness.
Materials and methods. The HPLC analysis was performed on a “Milichrome A-02” microcolumn liquid chromatograph under the following conditions: a reversed-phase variant, 2 × 75 mm column filled with a non-polar sorbent Prontosil 120-5 C18 AQ, 5 μm; the mobile phase in the mode of a linear gradient – from eluent А (5 % of acetonitrile and 95  % of a buffer solution) to eluent B (100 % of acetonitrile) for 40 min. The flow rate of the mobile phase was 100 μL/min; the injection volume was 4 μL. The multichannel detection of the substance
was carried out using an UV-detector at 210, 220, 230, 240, 250, 260, 280 and 300 nm; the optimal value of the column temperature was 37 – 40 °С, and the pump pressure was 2.8 – 3.2 MPa.
Results and discussion. As a result of the studies performed, the retention parameters of loratadine and spectral relationships were determined using the unified HPLC method. This made it possible to include the results obtained in the database for the identification of antihistamines in the therapeutic monitoring of the treatment with an individual drug or in the complex treatment of allergic reactions. The development of the quantitative determination
of loratadine by HPLC on model solutions using various concentrations of the drug was carried out. The content of loratadine was determined by the equation S = 1.14 × 10-3C – 0.50 × 10-4; the correlation coefficient was 0.9998. It was found that the relative standard deviation RSD did not exceed 0.93 % when analyzing loratadine in the model solutions by HPLC.
Conclusions. The identification and the quantitative determination of loratadine by the unified HPLC method have been conducted. The method allows obtaining reliable and reproducible research results. The results of the studies can be recommended for implementation in the practice of forensic bureaus, toxicological centers, and clinical laboratories.

Crocus sativus L. from the Iridaceae family is a medicinal and edible plant that has recently been actively cultivated in Ukraine. Saffron spice is crocus flower stigmas exhibiting a wide range of the pharmacological activity due to its three main bioactive compounds: crocin, picrocrocin and safranal. The quality of this raw material is regulated
by various normative documents, but there is no monograph in the State Pharmacopoeia of Ukraine (SPhU).

Aim. To perform a comparative analysis of the monograph “Saffron for homoeopatic preparations” from the Ph. Eur. 9.0, “Saffron. Croci stigma” from the Deutscher arzneimittel codex (DAC) and “Spices – Saffron (Crocus sativus L.)” from the ISO 3632 by the following indicators: description, identifcation (microscopy and TLC), impurities, loss on drying, total ash and quantifcation of crocin, picrocrocin and safranal by UV-Vis-spectrophotometry to clarify the possibility of harmonizing the requirements of the national legal framework for Crocus stigmas with
the Ph. Eur. 9.0, DAC and ISO 3632. The results of the analysis will be taken into account in the development of the monograph of the national part of the SPhU “Crocus stigmas (saffron)”.
Results and discussion. The quality indicators of Crocus stigmas and their standardization determined
by the monograph in the Ph. Eur. 9.0, DAC and ISO 3632 on the raw material studied have been analyzed; some differences in the regulated quality indicators of the raw material have been found. The results of our own research have shown that the samples of the Ukrainian Crocus (saffron) meet all these requirements. The results of the macro- and microscopic examination of the raw material are given. The chromatographic examination has
been performed in accordance with the Ph. Eur. 9.0 and DAC using crocin as a standard compound; the quantitative determination of crocin, picrocrocin and safranal in 8 samples of Crocus stigmas has been performed by UV-Vis-spectrophotometry in accordance with the ISO 3632. It has been proposed to introduce the following indicators to determine the specifc absorption rate: for crocin (C₄₄H₆₄O₂₄; Mw – 976.70) not less than 180, for safranal (C₁₀H₁₄O; Mw – 150.22) – not less than 30, for picrocrocin (C₁₆H₂₆O₇; Mw – 330.37) – not less than 60 calculated with reference to the dried raw material.
Experimental part. For analysis the dried stigmas of Crocus sativus (saffron) collected in the village
Lyubimivka, Kherson region, Ukraine (2016-2018), as well as commercial samples of saffron from Morocco,
Azerbaijan, Spain were used. The analysis of the leading normative documents containing monographs “Crocus stigmas”, among them the Eur. Ph. 9.0, DAC and ISO 3632, was performed. The studies included description of the appearance of the whole Crocus stigmas; loss on drying and the mass fraction of volatile compounds (105 °C, 16 h); the mass fraction of total ash. The amount of picrocrocin, safranal and crocin was measured by direct reading of the absorption of 1 % aqueous solution of stigmas at 257 nm, 330 nm and 440 nm, respectively, using
a UV-Vis-spectrophotometer.
Conclusions. The analysis of the requirements to quality of the medicinal raw material – stigmas of Crocus sativus – has been performed based on the monographs: “Saffron for homoeopatic preparations” from the Ph. Eur. 9.0, “Saffron. Croci stigma” from the Deutscher arzneimittel codex and “Spices – Saffron (Crocus sativus L.)” from the ISO 3632. The main criteria for standardization of the raw material have been determined. It has been proposed to introduce the monograph to the national part of the SPhU “Crocus stigmas (saffron)” according to the following requirements: identifcation (macro- and microscopic signs; thin-layer chromatography (crocin); the quantitative
determination (the content of crocin, picrocrocin and safranal) adapted to the ISO 3632, performed by UV-Vis-spectrophotometry; impurities; loss on drying; total ash.
Key words: standardization; State Pharmacopoeia of Ukraine; Crocus sativus stigma; saffron; crocin

A series of compounds containing heterocyclic cores and gem-difluorocycloalkyl substituents was obtained under conditions of the parallel synthesis (i.e., simultaneous performance of reaction procedures, treatment of the reaction mixture, and product isolation for a number of similar transformations) using the reductive amination – the “Nitrogen deletion” reaction sequence. The synthesis of the target compounds commenced from heteroaromatic aldehydes and the corresponding gem-difluorocycloalkyl or (gem-difluorocycloalkyl)methyl amines and included the NaBH₃CN-mediated reductive amination and “Nitrogen deletion” upon the action of Levin’s anomeric amide. It has been shown that the method can be used to obtain compounds with the aforementioned structural fragments separated by one or two methylene units. The developed protocol allowed for the preparation of a 12-member compound library (67 % synthetic efficiency). Therefore, this novel synthetic methodology is suitable for decorating heterocyclic cores with sp³-enriched substituents that are attractive for medicinal chemistry.

Aim. To generalize and systematize information on the properties of modern chemical disinfectants and antiseptic agents (DA and AA) – peroxide compounds, surfactants, salts of heavy metals and metals of variable valence in the highest oxidation state, alcohols, phenols and quaternary ammonium salts.
Results and discussion. The classification of DA and AA by the chemical structure was performed. The spectrum of their activity, directions and forms of DA and AA were given. Toxicity and the impact on the environment were described.
Conclusions. The results of the study conducted allow us to state that modern DA and AA of a wide spectrum of action are peracetic acid and, to a certain extent, hydrogen peroxide. However, they are unstable in dilute solutions. Other reagents are chemically stable, but they are characterized by a weak or average action against spores and viruses. The most effective DA and AA are mixtures
(combinations) of compounds belonging to different classes. The examples of these combinations are “surfactants + biguanidine derivatives”; “quaternary ammonium salts + phenol derivatives”; “surfactants + aldehydes”; “quaternary ammonium salts + hydrogen peroxide”. These mixtures combine the advantages and compensate for the disadvantages of individual DA and AA.

Aim. To generalize and systematize information on titrimetric methods for determining quaternary ammonium compounds (QACs).
Results and discussion. The review summarizes and systematizes information on the properties of surfactants, provides their classification, shows the main ways of use in the national economy, and their role in pharmacy and medicine. Currently known titrimetric methods for determining cationic surfactants (СS), in particular quaternary ammonium compounds, which are widely used in medicine and pharmacy, are described and summarized.
Conclusions. As a result of the study, the main directions of developing methods for determining QACs by titrimetry methods have been summarized; the disadvantages and advantages of each of the methods described have been shown. In the future, it can be the basis for developing new and more effective methods of analysis.

An important step in creation of potential drugs is to confirm the structure of the compounds synthesized. This requires the use of modern physical and physico-chemical methods of research. Nowadays a promising scientific direction for searching biologically active substances is the study of 2-R-imino-1,3-thiazoline derivatives.

Aim. To study regioselectivity of the cyclization reaction of 1-ethyl-3-[4-(6,7,8,9-tetrahydro-5Н-[1,2,4]triazolo[4,3-а]azepin-3-yl)phenyl]thiourea with 2-bromo-1-phenylethanone.

Results. The true structure of the interaction product was determined by the methods of ¹H NMR spectroscopy and X-ray analysis. Quantum chemical calculations of the electronic structure, geometry and thermodynamic parameters of the initial thiourea three tautomers were given. Activating energy of tautomer 1A belower than 1B one, the state of 1B has modest lower relative energy, consequently tautomer 1A is more credible state. Thus, the conclusion can be made that the reaction will proceed by 1-1A-3A.

Experimental part. Quantum chemical calculations of the electronic structure, geometry and thermodynamic parameters of the initial thiourea three tautomers were determined by the density functional theory (DFT) methods using the GAUSSIAN W09 computer program. The effect of the solvent was considered within the framework of polarized continuum model (PCM).

Conclusions. Based on the physico-chemical studies and quantum chemical calculations of the reaction cyclization direction the conclusion has been made that the cyclization reaction of 1-ethyl-3-[4-(6,7,8,9-tetrahydro-5H-[1,2,4]triazolo[4,3-а]azepin-3-yl)phenyl]thiourea 1 with 2-bromo-1-phenylethanone 2 is regioselective, and it leads to formation of more thermodynamically advantageous (stable) isomer 3A. 

Aim. DNA-encoded libraries technologies (DELT) are gradually becoming an important part of standard drug discovery toolbox. DELT is looking to find its place between classic low-molecular-weight drug candidates on the one hand, and high-molecular-weight antibodies and peptides on the other hand. On its natural path to overcoming the “childhood diseases” typical for every novel technology, DELT has reached a point where the chemical diversity of DNA-encoded libraries (DELs) becomes an important factor to look out for. In this paper, we aim to take a closer look at the chemical diversity of DELs in their present state and find the ways to improve it.
Results and discussion. We have identified the DEL-viable building blocks from the Enamine Ltd. stock collection, as well as from Chemspace Ltd. virtual collection, using the SMARTS set, which takes into account all the necessary structural restrictions. Using modern cheminformatics tools, such as Synt-On, we have analyzed the scaffold diversity of both stock and virtual core bi- and tri-functional building blocks (BBs) suitable for DNA-tolerant reactions. The identification of scaffolds from the most recently published on-DNA heterocyclization reactions and analysis of their inclusion into the existing BBs space have shown that novel DNA-tolerant heterocyclizations are extremely useful for expanding chemical diversity in DEL technologies.
Conclusions. The analysis performed allowed us to recognize which functional groups should be prioritized as the most impactful when the new BBs are designed. It is also made clear that the development of new DNA-tolerant reactions, including heterocyclizations, have a significant potential to further expand DEL molecular diversity.

An optimized approach towards 4-substituted 2,4-methanoproline derivatives is reported. Careful selection of the starting materials and optimized isolation procedure provided easy access to a key bicyclic building block in a preparative yield of 32% over five laboratory steps of up to 0.7 kg. Further modifications allowed us to obtain a number of useful derivatives, including those containing NH₂, COOH, CH₂NH₂, and CH₂F fragments with orthogonally protected functionalities.

A simple and efficient method for synthesizing aromatic compounds with a difluoro(methoxy)methyl fragment (CF₂OCH₃) by the fluorodesulfurization of thionoesters has been developed. Systematic screening identified SnCl₄/DAST as the optimal reagent combination, providing excellent selectivity and high yields of target products. A series of aromatic difluoro(methoxy)methyl compounds was synthesized under these conditions. Further studies of the electronic properties of the difluoro(methoxy)methyl group using ¹⁹F NMR allowed us to determine its Hammett constants for inductive (σ_I) and resonance (σ_R) effects. The results show that CF₂OCH₃ acts as a moderately electron-withdrawing substituent, underscoring its potential as a versatile group for designing organic molecules with precisely tuned electronic characteristics.

The review summarizes and systematizes data of the last twenty years on the synthetic methods and biological properties of pyrido[2,3-d]pyrimidin-7-ones, promising objects of organic and pharmaceutical chemistry. Two main approaches to the formation of the pyrido[2,3-d]pyrimidine system are considered. The first of them involves the cyclization of substituted pyridines containing functional groups in positions 2 and 3 of the heterocyclic ring. The second approach is based on the formation of a bicyclic system by adding a pyridone moiety to the pyrimidine ring. The methods developed allow to introduce various functional groups and aromatic substituents into the pyrido[2,3-d]pyrimidine system, as well as to obtain most of the target products with high yields. The effective three-component one-pot synthetic approaches to the formation of pyridine ring with the participation of functionalized pyrimidines and compounds with an active methylene group have been proposed. The analysis of the literature has shown that functionalized pyrimidines are the most common starting reagents, which structural modification is useful for the further annelation of the pyridine cycle. Much attention is paid to the biological properties of pyrido[2,3-d]pyrimidin-7-ones. The prospect of using pyrido[2,3-d]pyrimidin-7-one derivatives as tyrosine kinase inhibitors has been shown. Data on the biological effects of pyrido[2,3-d]pyrimidin-7-one derivatives indicate the possibility of detecting new biologically active compounds among pyridopyrimidines.

Much attention is currently paid to the study of the antioxidant properties of various objects – individual antioxidants, dietary supplements, medicines, liquid plant extracts. Antioxidant medicines are widely used as the main or additional correction agents in the treatment of a number of diseases. Therefore, the study and development of procedures for determining the antioxidant activity is a prospective task for today.

Aim. To determine the contribution of different concentrations of ethanol to the level of the antioxidant activity (AOA) of ascorbic acid solutions by the potentiometric method.

Results and discussion. The different ethanol content in the solution had the following percent of the contribution to the value of AOA of ascorbic acid solutions – 1.85, 3.56, 4.89, 6.76, 7.63 % for 20, 40, 60, 80, 96 % ethanol, respectively. The linearity of the procedure was proven in the range from 0.039 to 0.31 mmol/L.

Experimental part. The object of the study was solutions of ascorbic acid prepared using ethanol of different concentrations – 20, 40, 60, 80, 96 %. Potentiometric measurements were conducted by a Hanna 2550 pH meter (Germany) with an EZDO 5010 combined platinum electrode. Weighing was carried out using an АN100 digital analytical balance (AXIS, Ukraine) with d = 0.0001 g. Ascorbic acid was purchased from Sigma Aldrich (≥ 99.0 %), K₃[Fe(CN)₆], K₄[Fe(CN)₆], NaHPO₄, KH₂PO₄ were of analytical grade.

Conclusions. It has been found that ethyl alcohol affects the change of the potential in the electrochemical cell and the level of AOA of ascorbic acid solutions. The percentage of the contribution of different concentrations of ethyl alcohol to the AOA value ranges from 1.85 to 7.63 %. The approach and the formula for calculation that take into account the effect of ethyl alcohol on the final AOA result of the test sample of ascorbic acid in a water-alcohol solutions have been proposed. The results of this study can be used in the pharmaceutical and food industries to determine, assess and control the AOA level of dietary supplements, liquid extracts, tinctures, medicines, and alcoholic beverages.

Aim. To demonstrate the advantages of large-scale virtual libraries generated using chemical protocols previously validated in primary steps of the drug discovery process.
Results and discussion. Two validated parallel chemistry protocols reported earlier were used to create the chemical space. It was then sampled based on diversity metric, and the sample was subjected to the virtual screening on BRD4 target. Hits of virtual screening were synthesized and tested in the thermal shift assay.
Experimental part. The chemical space was generated using commercially available building blocks and synthetic protocols suitable for parallel chemistry and previously reported. After narrowing it down, using MedChem filters, the resulting sub-space was clustered based on diversity metrics. Centroids of the clusters were put to the virtual screening against the BRD4 active center. 29 Hits from the docking were synthesized and subjected to the thermal shift assay with BRD4, and 2 compounds showed noticeable dTm.
Conclusions. A combination of cheminformatics and molecular docking was applied to find novel potential binders for BRD4 from a large chemical space. The selected set of predicted molecules was synthesized with a 72 % success rate and tested in a thermal shift assay to reveal a 6 % hit rate. The selection can be performed iteratively to fast support of the drug discovery.

Metronidazole belongs to the group of antiprotozoal medicines and is a potential object of research in various areas of analytical toxicology.

Aim. To study the metronidazole behavior when developing with color reagents generally accepted and to determine R_f values of metronidazole under chromatographing conditions in the solvent systems generally accepted in forensic toxicology.

Results and discussion. It has been shown that such widely used color reagents as UV-light, iodine vapor, Wagner reagent, acidified iodoplatinate solution can be used for detecting metronidazole on chromatographic plates. Metronidazole gives positive detection results with reagents used in the TLC-screening of extracts from the biological material for substances of basic, acid and neutral nature. It has been proposed to develop metronidazole with the neutral ninhydrin solution, p-dimethylaminobenzaldehyde solution and hydrochloric acid vapors, as well as acidified iodoplatinate solution after keeping the plates in formalin vapors. The chromatographic mobility of metronidazole has been studied in 17 solvents systems; the systems are used as standard mobile phases according to recommendations of the International Association of Forensic Toxicologists for TLC-screening of organic compounds of acid, neutral and basic nature, in the general TLC-screening of organic substances in the Ukrainian forensic toxicological laboratories, and some systems investigated with the purpose of choosing the optimal individual solvents systems for the metronidazole study.

Experimental part. The chromatographic plates Sorbfil® PTLC-IIH-UV and Merck® TLC SILICA GEL 60 were used as thin layers.

Conclusions. The behavior of metronidazole when developing on TLC-plates with two types of a substrate (plastic and glass) and with/without luminophor (or UV-indicator) with commonly used colored reagents has been studied. The R_f values of metronidazole under chromatographing conditions in the standard solvent systems used for TLC-screening of organic compounds of acid, neutral and basic nature have been determined.

Aim. To develop a principally new method, which would allow achieving the necessary accuracy and reproducibility of the analysis results, for determining the activity of the blood cholinesterase; to create safe working conditions when performing the analysis.

Results and discussion. The kinetic method proposed for determining the activity of cholinesterase consists in photometric measurement of the rate of the enzymatic hydrolysis of the acetylcholine substrate (by its residue) in the phosphate buffer using p-phenetidine as an indicator. The rate of the enzymatic hydrolysis of acetylcholine was determined by the tangent of the inclination angle of the linear part of the kinetic curve in the А–t coordinates at a wavelength of 358 nm. The linear dependence of the conditional reaction rate (tgα) on the enzyme concentration was observed in the concentration range of 0.12 – 0.36 mg/mL. Metrological characteristics of the method developed were: RSD = 2.0 % (n = 5; P = 0.95), correctness 0.4 %. These values indicate that the method for determining the activity of blood cholinesterase is sensitive, reliable and reproducible.

Experimental part. The experiments on determining the rate of the enzymatic hydrolysis were repeated three times with a specific concentration of the enzyme. Using the data obtained the kinetic curves were constructed in the А–t coordinates; on their basis the tangents of the angles of inclination in min^-1 were calculated. The calibration graph was constructed using the average values of the tangents of the angles of inclination, which corresponded to a certain concentration of the solution of the working standard sample of the enzyme. The equation of the calibration dependence of tgα-enzyme concentration was calculated by the method of least squares and found to be tgα (min^-1) = –0.17с + 9.13 (r = 0.999).

Conclusions. As a result of the studies conducted, a new method for determining the activity of the cholinesterase enzyme has been developed. The method is characterized by a high sensitivity, reliability and reproducibility and provides safe working conditions when performing the analysis.

Fused heterocyclic 1,2,4-triazoles have provided much attention due to variety of their interesting biological properties.

Aim. To develop the method for the synthesis of novel 2-[(1,2,4-oxadiazol-5-yl)-[1,2,4]triazolo[4,3-a]pyridine-3-yl]acetamides and conduct the biological assessment of the compounds synthesized.

Results and discussion. A diverse set of acetamides newly synthesized consists of 32 analogs bearing an 1,2,4-oxadiazole cycle in positions 6, 7 and 8. A convenient scheme of the synthesis starts from commercially available 2-chloropyridine-3-, 2-chloropyridine-4-, 2-chloropyridine-5-carboxylic acids with amidoximes to form the corresponding 2-chloro-[3-R₁-1,2,4-oxadiazol-5-yl]pyridines, then follows the reaction of  hydrazinolysis with an excess of hydrazine hydrate. The process continues via the ester formation with the pyridine ring closure, then the amide formations of the end products are obtained by hydrolysis into acetic acid.

Experimental part. A series of new 2-[6-(1,2,4-oxadiazol-5-yl)-, 2-[7-(1,2,4-oxadiazol-5-yl)-, 2-[8-(1,2,4-oxadiazol-5-yl)-[1,2,4]triazolo[4,3-a]pyridine-3-yl]acetamides were obtained in good yields, and their structures were proven by the method of ¹H NMR spectroscopy. The prognosis and study of their pharmacological activity were also conducted.

Conclusions. The synthetic approach of obtaining the representatives of 2-[(1,2,4-oxadiazol-5-yl)-[1,2,4]triazolo[4,3-a]pyridine-3-yl]acetamides previously unknown can be used as an applicable method for the synthesis of diverse functionalized [1,2,4]triazolo[4,3-a]pyridine derivatives.

Aim. To expand the range of 6-arylidene-2-methyl-2,3-dihydroimidazo[2,1-b]thiazolones as potential objects for studying the antiexudative and antimicrobial activities.

Results and discussion. It has been shown that the condensation of synthetically affordable 2-methyl-2,3-dihydroimidazo[2,1-b]thiazolone with aromatic aldehydes can be successfully used for obtaining the corresponding 6-ylidene-functionalized derivatives. The biological screening of the compounds synthesized revealed that they possessed a low or moderate anti-inflammatory activity and inhibited the inflammation process in the range from 3 to 44 %. During the study of the antimicrobial activity of the substances obtained it was determined that their minimum bacteriostatic and minimum fungistatic concentrations ranged from 31.25 to 250 μg/mL.

Experimental part. The interaction of 2-methyl-2,3-dihydroimidazo[2,1-b]thiazolone with a series of benzaldehydes and salicylic aldehydes in refluxing acetic acid in the presence of anhydrous sodium acetate leads to new 6-arylidene-2-methyl-2,3-dihydroimidazo[2,1-b]thiazolones. The antiexudative activity screening was performed on the model of carrageenan-induced paw oedema of white outbred male rats. The antimicrobial activity of the compounds was studied using the microtechnique of two-fold serial dilutions in a liquid nutrient medium.

Conclusions. It has been found that the Knoevenagel condensation of 2-methyl-2,3-dihydroimidazo[2,1-b]thiazolone with aromatic aldehydes is a convenient way for the structural modification of the position 6 of the heterocyclic system by the arylidene moiety. The arylidene derivatives obtained show a moderate antiexudative activity in the carrageenan-induced rat paw oedema assay, as well as the antimicrobial activity against some gram-positive and gram-negative bacteria and fungi.

Aim. To provide a brief literature review regarding the structure of the human coronavirus SARS-CoV-2, the mechanism of its replication and the role of viral proteases in this process; to analyze the ability of the known antiviral agents and compounds synthesized de novo in order to bind and inhibit the coronavirus main protease using computer simulation tools.

Results and discussion. COVID-19 coronavirus has become a worldwide challenge in recent months. Taking into account the rapid spread and severity of COVID-19 among a significant part of the population there is an urgent need to develop effective medicines and appropriate treatment protocols, which, unfortunately, are not yet available. Currently, the search for molecules with an acceptable toxicity profile that are able to inhibit and/or stop coronavirus SARS-CoV-2 replication in the human body is very relevant. In this study, the virtual screening and molecular docking of both antiviral agents known and new compounds synthesized have been performed based on the structure of the main protease M^pro of SARS-CoV-2. The regularities identified during our study can be useful for searching and developing new antiviral drugs to control COVID-19 and other coronavirus infections. The analysis of the results of calculations of physicochemical characteristics of antiviral agents, as well as the determination of their binding sites with the main viral protease M^pro gives an optimistic assessment of the possibility to develop new drugs based on the structures of the known antiviral drugs or their modified analogs.

Experimental part. Based on recent studies of the crystal structure of the virus main protease M^pro in the complex with various inhibitors (Protein Data Bank http://www.rcsb.org/pdb, the structure code – 6LU7) the virtual screening and molecular docking of 100 known antiviral agents and 50 novel compounds synthesized were performed. The screening data for the in vitro antimalarial activity of the compounds synthesized were presented. The following binding and physicochemical parameters of the ligand–protein interaction for all virus main protease potential inhibitors were calculated: binding affinity score (BAS), binding energy, lipophilicity (clogP) and topological polar surface area (TPSA). The protein and ligand structures were studied using Jmol, PyMol, and Avogadro graphics software packages. The virtual screening and molecular docking, as well as the analysis of the results were performed using a LigandScout 4.4 software package. Data on the antimalarial activity of 50 compounds synthesized were obtained from the Laboratory of Microbiology, Parasitology and Hygiene of theUniversity ofAntwerp (Belgium).

Conclusions. According to the results of the virtual screening and molecular docking with protein 6LU7 it has been found that a number of the known antiviral drugs have a certain potential for their use as inhibitors of SARS-CoV-2 coronavirus main protease. Remdesivir and ritonavir substances have shown higher activity than the reference compound of the 6LU7 complex. The molecular docking of a series of compounds recently synthesized with the proven in vitro antimalarial activity has revealed that L1 – L6 compounds are promising candidates for further modification and development of new antiviral drugs to control coronavirus infection.

Received: 02.04.2020
Revised: 23.05.2020
Accepted: 29.05.2020