Corresponding author: Yevhen Karpun ( ekarpun@yahoo.com ) Academic editor: Plamen Peikov
© 2021 Yevhen Karpun, Volodymyr Parchenko, Tetiana Fotina, Denys Demianenko, Anatolii Fotin, Volodymyr Nahornyi, Natalia Nahorna.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Karpun Ye, Parchenko V, Fotina T, Demianenko D, Fotin A, Nahornyi V, Nahorna N (2021) The investigation of antimicrobial activity of some s-substituted bis-1,2,4-triazole-3-thiones. Pharmacia 68(4): 797-804. https://doi.org/10.3897/pharmacia.68.e65761
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New S-substituted 4-alkyl-5-((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio)methyl)-4H-1,2,4-triazole-3-thiol derivatives have been designed, synthesized and studied their antimicrobial activity on 11 standard Gram-positive and Gram-negative microorganism strains. Their spectral and physicochemical parameters were established using modern comprehensive methods of analysis, including 1H NMR spectroscopy, GC-MS and elemental analysis.It has been found that compound 2a exhibits strong suppression of 5 test strains (MBC = 15.6 µg/mL). Compound 4a showed moderate inhibition of Salmonella pullorum, Escherichia coli O2, Salmonella enteritidis strains (MBC = 31.25 µg/mL) Compound 6a was sensitive toward ten tested bacteria at 31.25 µg/mL concentration.
1, 2, 4-triazole, organic synthesis, antimicrobial activity
The currently rising numbers of drug-resistant bacterial pathogen strains disrupts the effectiveness of the existing treatments and amplifies the incidence of new bacterial infections. This circumstance urges researchers around the world to search for new effective and at the same time low-toxic medicines distinguished by innovative mechanisms of action, which is of the most significance for modern pharmaceutical science.
Organic compounds containing nitrogen atoms represent a large group of chemical structures, of both natural and synthetic origin, which may possess a broad range of biological activities. In this respect, 1,2,4-triazole system, a five-membered nitrogen-containing heterocycle, has arisen strong scientific interest (
The derivatives of 1,2,4-triazole are widely used in pharmaceutical and medicinal chemistry as well as in organic synthesis (
In our opinion, the investigation of the structures constructed using two bridged 1,2,4-triazole cycles belonging to various chemical classes may lead to the discovery of quite promising compounds that exhibit versatile antibacterial effects. The increase in the number of the system’s reaction sites enables sufficient variations of chemical modification of bis-1,2,4-triazole, which multiples the probability of finding active derivatives. During the recent years, there have been numerous publications on the syntheses of 1,2,4-triazole derivatives containing various pharmacophore frameworks that exhibit antimicrobial activity (
The purpose of this work was to synthesize new compounds based on 4-alkyl-5-(((3-(pyridin-4-yl)-1Н-1,2,4-triazole-5-yl)thio)methyl)-4Н-1,2,4-triazole-3-thiol, in which isopropyl 2-chloroacetate, 1-bromopentane and 2-chloroacetamid were used as alkylation agents, study the ammonolysis of the previously obtained isopropyl ester with methylamine, ethylamine, dimethylamine, diethylamine, morpholine and 2-methylpiperidine, study their physicochemical properties and confirm the structure of these derivatives using modern multidimensional methods of identification. Along with that, we attempted to investigate the antimicrobial activities of the compounds on standard Gram-positive and Gram-negative microorganism strains to evaluate the pharmacological potential of the substances. The ultimate purpose was to conduct the comparative analysis of the relationships between the antimicrobial activity and functional groups of these molecules.
Melting points were determined on OptiMelt MPA100 apparatus (USA) equipped with platinum RTD sensor and temperature measurement possibility of up to 400 °C and 0.1 °C resolution. Elemental analysis was performed on a Elementar Vario L cube multipurpose elemental analyzer (CHNS) produced by Analysen systeme GmbH (Germany) using sulfanilamide as the standard. The mass-to-charge ratio of S-derivatives of bis-1,2,4-triazole was been determined by gas chromatography via Agilent 7890B GC system equipped with Agilent 5977B mass spectrometry detector (USA). The column used for separation was DB-5ms. Type of ionization: electron impact (EI) with electron energy of 70 eV. 1H NMR spectra were recorded at 400 MHz and 100 MHz using Varian MR-400 spectrometer with DMSO-d6 as the solvent. Spectra were processed via ADVASP Analyzer software (Umatek International Inc.). Chemical shifts are reported in ppm (δ scale) down field with residual protons of the solvent (DMSO-d6) present at δ=2.49 ppm and using a common internal standard. Molecular docking was performed using Autodock 4.2.6. The screening was performed on the crystallographic structure of the enzyme “beta-lactamase cTEM-19m” (4R4S) (
Serial dilutions method was used to assess the sensitivity of the isolated microorganism strains to the experimental samples. The activity was studied according to the methodological recommendations (
The subject of the research
was represented by isopropyl 2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio)methyl)-4H-1,2,4-triazole-3-yl)thio)acetate (2a), isopropyl 2-((4-ethyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio)methyl)-4H-1,2,4-triazole-3-yl)thio)acetate (2b) , 2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio)methyl)-4H-1,2,4-triazole-3-yl)thio)acetamide (3a), 2-((4-ethyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio)methyl)-4H-1,2,4-triazole-3-yl)thio)acetamide (3b), (Fig.
Amines were also synthesized from compounds 2a 2b by amonolysis with the appropriate reagents (methylamine, ethylamine, dimethylamine, diethylamine, morpholine and 2-methylpiperidine). N-methyl-2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)acetamide (5a), 2-((4-ethyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)-N-methylacetamide (5b), N,N-dimethyl-2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)acetamide (6a), 2-((4-ethyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)-N,N-dimethylacetamide (6b), N-ethyl-2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)acetamide (7a), N-ethyl-2-((4-ethyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)acetamide (7b), N,N-diethyl-2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)acetamide (8a), N,N-diethyl-2-((4-ethyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)acetamide (8b), 2-((4-ethyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)-1-(2-methylpiperidin-1-yl)ethan-1-one (9b), 2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)-1-morpholinoethan-1-one (10a) (Fig.
The structures were synthesized at the Department of Natural Sciences for Foreign Students and Toxicological Chemistry of Zaporizhzhia State Medical University, according to a commonly known procedure; the compounds were further used in the investigation of their antimicrobial activity.
The synthesis of 4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio)methyl)-4H-1,2,4-triazole-3-thiol (1a,b) was performed using common and known procedures (
Isopropyl 2-chloroacetate, 2-chloroacetamid and 1-bromopentane were used as alkylation agents (Fig.
Based on the previous research, it was approved empirically that the introduction of functional groups at Sulfur atom of bis-1,2,4-triazole-3-thione leads to the increase of solubility in more polar substances due to the charge redistribution in the molecule and formation of intermolecular hydrogen bonds. The derivatives containing one 1,2,4-triazole cycle are practically insoluble in water and poorly soluble in highly polar solvents. However, a number of bis-1,2,4-triazoles are soluble in water, acetic acid, DMF and alcohols. This system is of great interest with regard to its biological activity since its reactivity is increased meaning a broader range of possible chemical modifications in various directions.
The structure of the synthesized bis-derivatives of 1,2,4-triazole was confirmed by a set of physical and instrumental analysis methods such as elemental analysis, 1H NMR spectrometry. The relative time and mass to charge ratio of the compounds was studied using GC-MS.
Isopropyl 2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio)methyl)-4H-1,2,4-triazole-3-yl)thio)acetate (2a). Yellow powder in 81% yield, m.p. 151–153 °C. 1H NMR (400 MHz, DMSO-d6) δ: 1.66 (br. s., 7 H), 2.00–2.07 (m, 3 H), 3.19 (br. s., 2 H), 3.65 (s, 2 H), 4.36 (s, 1 H), 7.77 (d, J=4.88 Hz, 2 H), 8.40 (d, J=5.19 Hz, 1 H). MS (m/z): 404 (M+). Anal. calcd for C16H19N7O2S2, % C 47.38; H 4.74; N 26.11, S 15.90. Found, % C, 47.39; H, 4.72; N, 24.18, S 15.82.
Isopropyl 2-((4-ethyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio)methyl)-4H-1,2,4-triazole-3-yl)thio)acetate (2b). Yellow powder in 68% yield, m.p. 118–120 °C. 1H NMR (400 MHz, DMSO-d6) δ: 1.52 (br. s., 7 H), 1.89–1.95 (m, 3 H), 3.19–3.25 (br. s., 4 H), 3.85 (s, 2 H), 4.36 (s, 1 H), 7.77 (d, J=4.88 Hz, 2 H), 8.40 (d, J=5.19 Hz, 2 H). MS (m/z): 420 (M+). Anal. calcd for C17H21N7O2S2, % C 48.65; H 5.04; N 23.44, S 15.20. Found, % C 48.67; H 5.05; N 23.37, S 15.29.
2-((4-Methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio)methyl)-4H-1,2,4-triazole-3-yl)thio)acetamide (3a). Yellow powder in 76% yield, m.p. 118–120 °C. 1H NMR (400 MHz, DMSO-d6) δ: 3.70–3.79 (s, 3 H); 4.36–4.39 (m, 2 H); 4.77 (s, 2 H); 7.77–7.82 (d, J=5.80 Hz, 2 H); 8.38–8.43 (m, 1 H). (M+). Anal. calcd for C13H14N8OS2 , % C 43.18; H 3.84; N 30.91, S 17.78. Found, % C 43.08; H 3.89; N 30.92, S 17.69%.
2-((4-Ethyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio)methyl)-4H-1,2,4-triazole-3-yl)thio)acetamide (3b). Yellow powder in 75% yield, m.p. 118–120 °C. 1H-NMR (400 MHz, DMSO-d6) δ: 1.63–1.69 (s, 3 H), 3.49–3.58 (br. s., 2 H), 4.47–4.52 (s, 2 H), 4.77–4.85 (s, 2 H), 7.73–7.83 (m, 2 H), 8.41–8.49 (t, J=4.43 Hz, 1 H). MS (m/z): 376 (M+). Anal. calcd for C14H16N8OS2, % C 44.78; H 4.60; N 29.71, S 17.01%. Found, % C 44.67; H 4.28; N 29.77, S 17.04.
4-(5-(((4-Methyl-5-(pentylthio)-4H-1,2,4-triazole-3-yl)methyl)thio)-1H-1,2,4-triazole-3-yl)pyridine (4a). Yellow powder in 85% yield, m.p. 118–120 °C. 1H-NMR (400 MHz, DMSO-d6) δ: 0.67–0.85 (m, 3H), 1.10–1.32 (m, 4H), 1.79–1.95 (m, 2H), 2.63 (br.s., 1 H), 3.82 (br.s., 3H), 4.07 (s, 2H), 4.49 (t, J=7.03, 2H), 7.83 (d, J=4.52, 2H); 8.65 (d, J=4.50 , 2H). MS (m/z): 375 (M+). Anal. calcd for C16H21N7S2, C, 51.18; H, 5.64; N, 26.11, S 17.08%. Found: C, 51.30; H, 5.60; N, 26.06, S 17.01%.
N-methyl-2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)acetamide (5a). Yellow powder in 85% yield, m.p. 139–141 °C. 1H NMR (400 MHz, DMSO-d6) d ppm 2.29 (q, J=6.10 Hz, 3 H), 3.54–3.61 (m, 3 H), 4.05–4.11 (m, 2 H), 4.34 (s, 2 H), 7.40 (s, 1 H), 8.14 (d, J=5.87 Hz, 2 H), 8.79 (d, J=5.62 Hz, 2 H). MS (m/z): 376 (M+). Anal. calcd for C14H16N8OS2, C, 44.67; H, 4.28; N, 29.77; S, 17.04%. Found: C, 44.58; H, 4.32; N, 29.86, S 16.96%.
2-((4-ethyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)-N-methylacetamide (5b). Orange powder in 78% yield, m.p. 145–147 °C. 1H NMR (400 MHz, DMSO-d6) d ppm 1.13 (t, J=6.10 Hz, 4 H), 3.88 (s, 2 H), 3.98 (q, J=6.20 Hz, 3 H), 4.28 (s, 2 H), 4.87 (q, J=4.80 Hz, 1 H), 7.84 (s, 3 H), 8.59–8.72 (m, 3 H). MS (m/z): 390 (M+). Anal. calcd for C15H18N8OS2, C, 46.14; H, 4.65; N, 28.70; S, 16.42%. Found: C, 46.20; H, 4.60; N, 28.76, S 16.38%.
N,N-dimethyl-2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)acetamide (6a). Yellow powder in 81% yield, m.p. 116–118 °C. 1H NMR (400 MHz, DMSO-d6) d ppm 2.82 (s, 6 H), 3.57 (s, 3 H), 4.05 (s, 2 H), 4.60 (s, 2 H), 7.82–7.88 (m, 3 H), 8.64–8.70 (m, 3 H). MS (m/z): 390 (M+). Anal. calcd for C15H18N8OS2, C, 46.14; H, 4.65; N, 28.70; S, 16.42%. Found: C, 46.24; H, 4.69; N, 28.66, S 16.31%.
2-((4-ethyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)-N,N-dimethylacetamide (6b). Orange powder in 77% yield, m.p. 142–144 °C. 1H NMR (400 MHz, DMSO-d6) d ppm 1.81 (t, J=6.10 Hz, 3 H), 3.04 (s, 5 H), 3.88–4.09 (m, 5 H), 4.82 (s, 2 H), 7.76–7.93 (m, 2 H), 8.56–8.70 (m, 2 H). MS (m/z): 404 (M+). Anal. calcd for C16H20N8OS2, C, 47.51; H, 4.98; N, 27.70; S, 15.85%. Found: C, 47.40; H, 4.99; N, 26.84, S 15.80%.
N-ethyl-2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)acetamide (7a). Yellow powder in 70% yield, m.p. 154–157 °C. 1H-NMR (400 MHz, DMSO-d6) δ ppm 1.19 (t, J=6.5 Hz, 3H), 3.27 (qd, J=6.4, 3.8 Hz, 2H), 3.57 (s, 2H), 3.83–3.87 (s, 2H), 4.57–4.63 (s, 2H), 7.40 (t, J=3.8 Hz, 1H), 7.89–7.94 (m, 2 H), 8.52–8.63 (m, 2 H).. MS (m/z): 390 (M+). Anal. calcd for C15H18N8OS2, C, 46.14; H, 4.65; N, 28.70; S, 16.42%. Found: C, 46.02; H, 4.69; N, 28.77, S 14.53%.
N-ethyl-2-((4-ethyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)acetamide (7b). Orange powder in 65% yield, m.p. 161–163 °C. 1H NMR (400 MHz, DMSO-d6) d ppm 0.95 (br. t, J=6.30, 6.30 Hz, 3 H), 1.12 (t, J=6.20 Hz, 3 H), 3.96 (qd, J=6.20, 5.40 Hz, 2 H), 4.10 (s, 2 H), 4.34 (q, J=6.00 Hz, 2 H), 5.13 (s, 2 H), 7.53 (t, J=4.20 Hz, 1 H), 8.14–8.34 (m, 2 H), 8.77–8.90 (m, 2 H). MS (m/z): 404 (M+). Anal. calcd for C16H20N8OS2, C, 47.51; H, 4.98; N, 27.70; S, 15.85%. Found: C, 47.56; H, 4.92; N, 27.76, S 15.81%.
N,N-diethyl-2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)acetamide (8a). Yellow powder in 72% yield, m.p. 163–165 °C. 1H NMR (400 MHz, DMSO-d6) d ppm 1.15 (t, J=7.21 Hz, 7 H), 2.83 (q, J=7.09 Hz, 4 H), 3.58 (s, 2 H), 4.24 (s, 2 H), 4.60 (s, 2 H), 7.84–7.91 (m, 2 H), 8.61–8.72 (m, 2 H). MS (m/z): 418 (M+). Anal. calcd for C17H22N8OS2, C, 48.79; H, 5.30; N, 26.77; S, 15.32%. Found: C, 48.85; H, 5.40; N, 26.68, S 15.24%.
N,N-diethyl-2-((4-ethyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)acetamide (8b). Orange powder in 80% yield, m.p. 147–149 °C. 1H NMR (400 MHz, DMSO-d6) d ppm 1.14 (t, J=7.34 Hz, 6 H), 1.81 (t, J=6.20 Hz, 1 H), 2.83 (q, J=7.17 Hz, 4 H), 3.94–4.02 (m, 4 H), 4.78 (s, 4 H), 7.79–7.90 (m, 2 H), 8.59–8.69 (m, 2 H). MS (m/z): 432 (M+). Anal. calcd for C18H24N8OS2, C, 49.98; H, 5.59; N, 25.91; S, 14.82%. Found: C, 49.87; H, 5.61; N, 26.02, S 14.84%.
2-((4-ethyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)-1-(2-methylpiperidin-1-yl)ethan-1-one (9b). Orange powder in 66% yield, m.p. 104–106 °C. 1H NMR (400 MHz, DMSO-d6) d ppm 3.02 (dd, J=5.10, 4.20 Hz, 4 H), 3.56 (s, 3 H), 3.77 (dd, J=5.30, 4.40 Hz, 4 H), 4.29 (s, 2 H), 4.59–4.69 (m, 2 H), 7.78–7.89 (m, 2 H), 8.58–8.68 (m, 2 H). MS (m/z): 458 (M+). Anal. calcd for C20H26N8OS2, C, 52.38; H, 5.71; N, 24.43; S, 13.98%. Found: C, 52.30; H, 5.82; N, 24.40, S 14.00%.
2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)-1-morpholinoethan-1-one (10a). Yellow powder in 69% yield, m.p. 151–153 °C. 1H NMR (400 MHz, DMSO-d6) d ppm 1.16 (d, J=6.36 Hz, 3 H), 1.39 (t, J=6.10 Hz, 3 H), 1.51–1.73 (m, 5 H), 1.80 (m, J=5.40 Hz, 1 H), 3.11–3.15 (m, 1 H), 3.76–3.83 (m, 1 H), 3.88 (br. dtd, J=6.60, 6.40, 6.40, 5.80 Hz, 1 H), 3.98 (d, J=15.60 Hz, 1 H), 4.22–4.36 (m, 3 H), 4.57–4.67 (m, 2 H), 7.75–7.91 (m, 2 H), 8.55–8.68 (m, 2 H). MS (m/z): 432 (M+). Anal. calcd for C17H20N8O2S2, C, 47.21; H, 4.66; N, 25.91; S, 14.82%. Found: C, 47.24; H, 4.61; N, 26 .06, S 17.01%.
The results of antimicrobial and antifungal activity of the alkylated bis-derivatives of 1,2,4-triazole with regard to the test cultures are presented in Table
Microorganism culture | Minimum bactericidal concentration (MBC), µg/cm3 | |||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
control | 2a | 2b | 3a | 3b | 4a | 5a | 5b | 6a | 6b | 7a | 7b | 8a | 8b | 9b | 10a | |
S. aureus | >250 | 31.25 | >250 | >250 | >250 | 125 | >250 | 31.25 | 31.25 | >250 | >250 | >250 | >250 | >250 | >250 | 125 |
S. fecalis | >250 | 15.6 | >250 | >250 | >250 | 125 | >250 | 31.25 | 31.25 | >250 | >250 | >250 | >250 | >250 | >250 | 125 |
S. pullorum | >250 | 15.6 | >250 | >250 | >250 | 62.5 | >250 | 31.25 | 31.25 | >250 | >250 | >250 | >250 | >250 | >250 | 62.5 |
S. typhimurium | >250 | 15.6 | >250 | >250 | >250 | 125 | >250 | 31.25 | 62.5 | >250 | >250 | >250 | >250 | >250 | >250 | 125 |
S. enteritidis | >250 | 31.25 | >250 | >250 | >250 | 62.5 | >250 | 31.25 | 31.25 | >250 | >250 | >250 | >250 | >250 | >250 | 62.5 |
E. coli O2 | >250 | 31.25 | >250 | >250 | >250 | 62.5 | >250 | 31.25 | 31.25 | >250 | >250 | >250 | >250 | >250 | >250 | 62.5 |
P. vulgaris | >250 | 31.25 | >250 | >250 | >250 | 125 | >250 | 31.25 | 31.25 | >250 | >250 | >250 | >250 | >250 | >250 | 62.5 |
P. aeruginosa | >250 | 31.25 | >250 | >250 | >250 | 62.5 | >250 | 31.25 | 31.25 | >250 | >250 | >250 | >250 | >250 | >250 | 62.5 |
K. pneumoniae | >250 | 15.6 | >250 | >250 | >250 | 31.25 | >250 | 31.25 | 31.25 | >250 | >250 | >250 | >250 | >250 | >250 | 62.5 |
C. perfringens | >250 | 31.25 | >250 | >250 | >250 | 125 | >250 | 31.25 | 62.5 | >250 | >250 | >250 | >250 | >250 | >250 | 125 |
According to the results of the preliminary microbiological screening, only five of the 4-alkyl-5-(((3-(pyridin-4-yl)-1Н-1,2,4-triazole-5-yl)thio)methyl)-4Н-1,2,4-triazole-3-thiol derivatives (2a, 4a, 5b, 6a, 10a) demonstrate the antimicrobial effect. Unfortunately, other compounds did not exhibit any growth inhibition of the studied strains even at the concentration of 250 µg/cm3.
For molecular docking, the cTEM-19m beta-lactamase enzyme (PDB ID: 4R4S, 1.1 Å) was chosen, which is synthesized by the bacteria E. coli О2 and K. pneumoniae, due to which the strains acquire resistance to many antibiotics. Compounds 2a and 5b were selected based on analysis of data of antimicrobial activity as potential inhibitors of beta-lactamase. The interaction of the ligand with the active center of the enzyme is complex and is provided mainly by alkyl bonds, ionic and conventional hydrogen bonds with water molecules and amino acid residues of the enzyme. An important point for binding to the enzyme is the presence of a sulfur atom in the molecules of the test compounds (Fig.
Visualization of the 3D structure of the “ligand-enzyme” complex is shown in (Fig.
In Fig.
Taking into account the previous research, it is safe to say that a great number of 1,2,4-triazole derivatives show considerable capabilities for suppressing the growth of pathogenic bacteria (
The investigation of the antimicrobial activity of the obtained compounds showed that at the concentration of 10 mg/mL five S-derivatives of bis-1,2,4-triazole (2a, 4a, 5b, 6a, 10a) exhibit bactericidal activity against all bacterial strains used in this study, and specifically Staphylococcus aureus, Enterococcus faecalis, Salmonella pullorum, Salmonella typhimurium, Salmonella enteritidis, Escherichia coli O2, Proteus vulgaris, Pseudomonas aeruginosa, Klebsiella pneumoniae, Clostridium perfringens.
Based on the obtained data, it is correct to submit that isopropyl 2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio)methyl)-4H-1,2,4-triazole-3-yl)thio)acetate (2a) exhibits strong antimicrobial activity against the strains of Enterococcus faecalis, Salmonella pullorum, Salmonella typhimurium (MBC = 15.6 µg/mL). The change of ethyl substituent into methyl at the 4-position of the second 1,2,4-triazole ring in isopropyl ether of bis-1,2,4-triazole acetic acid leads to the appearance of strong bactericidal activity against all of the studied strains.
It was established that isopropyl 2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio)methyl)-4H-1,2,4-triazole-3-yl)thio) acetate (2a) exhibits strong suppression of Klebsiella pneumoniae test strain (MBC = 31.25 µg/mL). Compound 4-(5-(((4-methyl-5-(pentylthio)-4H-1,2,4-triazole-3-yl)methyl)thio)-1H-1,2,4-triazole-3-yl)pyridine (4а) showed moderate inhibition of Salmonella pullorum, Escherichia coli O2, Salmonella enteritidis strains (MBC = 31.25 µg/mL). Novel 2-((4-ethyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazol-5-yl)thio)methyl)-4H-1,2,4-triazol-3-yl)thio)-N-methylacetamide (5b) slightly active at 31.25 µg/mL concentrations toward all strains. Compounds 6a and 10a were sensitive toward ten tested bacteria at 31.25 µg/mL to 125 µg/mL concentrations. On the other hand, the remaining amides (6a, 6b, 7a, 7b, 8a, 8b, 9b) did not show activity at 250 µg/mL concentrations.
The main disadvantages that may be pointed out from the serial dilution include the time restriction for conducting the research and expansion of the error during the consecutive dilutions. In the first case, time limitation is specific to the serial dilution method, due to which the prepared media must be used immediately, without the possibility of storage. As for the second case, the most considerable error is assigned to the most concentrated solution. In order to compensate for the error, longer mixing times are required, which makes the serial dilution more time-consuming.
The results of the preliminary research of antimicrobial activity of the synthesized S-substituted bis-1,2,4-triazoles demonstrate the promise of further studies of their biological properties, while also the targeted synthesis of new 1,2,4-triazoles possessing bactericidal activity represents great scientific interest.
The authors have no support to report.