Silver Complexes Research Articles

Silver(I) complexes with voriconazole as promising anti-Candida agents

Recognizing that metal ions play an important role in modifying the pharmacological properties of known organic-based drugs, the present manuscript addresses the complexation of the antifungal agent voriconazole (vcz) with the biologically relevant silver(I) ion as a strategy for the development of new antimycotics. The synthesized silver(I) complexes with vcz were characterized by mass spectrometry, IR, UV–Vis and NMR spectroscopy and single-crystal X-ray diffraction analysis. The crystallographic results showed that complexes {[Ag(vcz)(H2O)]CH3SO3}n (1), {[Ag(vcz)2]BF4}n (2) and {[Ag(vcz)2]PF6}n (3) have polymeric structures in the solid state, in which silver(I) ions have a distorted tetrahedral geometry. On the other hand, DFT calculations revealed that the investigated silver(I) complexes 1–3 in DMSO exist as linear [Ag(vcz-N2)(vcz-N19)]+ (1a), [Ag(vcz-N2)(vcz-N4)]+ (2a) and [Ag(vcz-N4)2]+ (3a) species, respectively. The evaluated complexes showed an enhanced anti-Candida activity compared to the parent drug with minimal inhibitory concentration (MIC) values in the range of 0.02–1.05 μM. In comparison with vcz, the corresponding silver(I) complexes showed better activity in prevention hyphae and biofilm formation of C. albicans, indicating that they could be considered as promising agents against Candida that significantly inhibit its virulence. Also, these complexes are much better inhibitors of ergosterol synthesis in the cell membrane of C. albicans at the concentration of 0.5 × MIC. This is also confirmed by a molecular docking, which revealed that complexes 1a – 3a showed better inhibitory activity than vcz against the sterol 14α-demethylase enzyme cytochrome P450 (CYP51B), which plays a crucial role in the formation of ergosterol.

Tuning the CO2 Reduction Selectivity of an Immobilized Molecular Ag Complex beyond CO.

The electrochemical reduction of carbon dioxide (CO2) to produce fuels and chemicals has garnered significant attention. However, achieving control over the selectivity of the resulting products remains a challenging task, particularly within molecular systems. In this study, we employed a molecular silver complex immobilized on graphitized mesoporous carbon (GMC) as a catalyst for converting CO2 into CO, achieving an impressive selectivity of over 90% at -1.05 V vs RHE. Notably, the newly formed silver nanoparticles emerged as the active sites responsible for this high CO selectivity rather than the molecular system. Intriguingly, the introduction of copper ions into the restructured Ag-nanoparticle-decorated carbon altered the product selectivity. At -1.1 V vs RHE in 0.1 M KCl, we achieved a high C2 selectivity of 75%. Furthermore, not only the Ag-Cu bimetallic nanoparticle but also the small-sized Ag-Cu nanocluster decorated over GMC was proposed as active sites during catalytic reactions. Our straightforward approach offers valuable insights for fine-tuning the product selectivity of immobilized molecular systems, extending beyond C1 products.

Silver Organometallics that are Highly Potent Thioredoxin and Glutathione Reductase Inhibitors: Exploring the Correlations of Solution Chemistry with the Strong Antibacterial Effects.

The antibacterial activity of silver species is well-established; however, their mechanism of action has not been adequately explored. Furthermore, issues of low-molecular silver compounds with cytotoxicity, stability, and solubility hamper their progress to drug leads. We have investigated silver N-heterocyclic carbene (NHC) halido complexes [(NHC)AgX, X = Cl, Br, and I] as a promising new type of antibacterial silver organometallics. Spectroscopic studies and conductometry established a higher stability for the complexes with iodide ligands, and nephelometry indicated that the complexes could be administered in solutions with physiological chloride levels. The complexes showed a broad spectrum of strong activity against pathogenic Gram-negative bacteria. However, there was no significant activity against Gram-positive strains. Further studies clarified that tryptone and yeast extract, as components of the culture media, were responsible for this lack of activity. The reduction of biofilm formation and a strong inhibition of both glutathione and thioredoxin reductases with IC50 values in the nanomolar range were confirmed for selected compounds. In addition to their improved physicochemical properties, the compounds with iodide ligands did not display cytotoxic effects, unlike the other silver complexes. In summary, silver NHC complexes with iodide secondary ligands represent a useful scaffold for nontoxic silver organometallics with improved physicochemical properties and a distinct mechanism of action that is based on inhibition of thioredoxin and glutathione reductases.

A promising perspective through potential antimicrobial, anti‐cancer, and antiviral activity against SARS‐CoV‐2 of silver(I) complexes: Synthesis, characterization, density functional theory calculations, and in‐silico molecular docking studies

This study tends to accomplish the sustainable development goal, which calls for all healthy lives. Antibiotic resistance, cancer, and severe acute respiratory syndrome coronavirus all showed high death rates in recent years. Our approach is to make better medications available to fight these feared health issues. In this context, three silver(I) complexes (1–3) based on the antibiotic gemifloxacin (HGMF) were synthesized and thoroughly examined using analytical, spectral, and thermal methods. The density functional theory suggested that complex 1 has a bent coordination environment while 2 and 3 have a distorted trigonal planar geometry. The optimal donor and acceptor centers were determined by the natural‐bond orbital analysis. Interaction of complexes with calf‐thymus DNA has been investigated and their binding constants were ordered as 3 > 2 > 1. The antimicrobial activity against 10 pathogenic microorganisms demonstrated that complex 3 exhibited superior activity compared with standard antibiotics. Testing against mammalian cell lines, liver carcinoma, breast carcinoma, and colon carcinoma revealed that complex 3 showed remarkable cell growth inhibition activity with IC50 values ranging from 3.0 to 9.3 μg/mL. Studies of Molecular docking against SARS‐CoV‐2 main protease Mpro (ID: 6 WTT) proved a powerful type of interaction at the active site. Complex 3 exhibits a potent inhibition effect with a total binding energy of −12.58 kcal/mol compared with the reference ligand inhibitor K36 suggesting its ability to block viral protease. This study presents promising bioactive candidates that have a practical impact on various medicinal fields.

Effect of fluorination on the cytotoxic potentials of benzimidazolium-based N-heterocyclic carbene ligands and their silver(I) complexes

The current study reports a new series of fluorinated benzimidazolium salts and their silver(I) complexes. The ligands were prepared via N-alkylation of 1-decylbenzimidazole with benzyl/fluorinated benzyl bromides. In situ deprotonation of the salts with silver oxide and metathesis reaction with potassium hexafluorophosphate yielded the mononuclear silver(I)–NHC complexes. All compounds were characterized using FTIR and NMR spectroscopies, CHN elemental analysis and liquid chromatography-time-of-flight mass spectrometry (LCMS-TOF). The in vitro cytotoxic activities of the ligands and complexes against human cervical cancer (HeLa), estrogen-positive human breast cancer (MCF-7) and triple-negative human breast cancer (MDA-MB-231) cells were evaluated using the MTT assay. All compounds exhibited remarkable growth inhibition against these cells, superior to etoposide, a clinical anticancer drug. Fluorination exerted different growth inhibition effects against HeLa, MDA-MB-231 and MCF-7 cells. Fluorination modulated the growth inhibition potencies of the salts and complexes against HeLa but had no enhancement effect against MCF-7 and MDA-MB-231. Incorporating silver(I) ions enhanced the cytotoxicity of the complexes against all tested cell lines (IC50: 0.46–1.36 µM).

Gold(I) and Silver(I) Complexes Containing Hybrid Sulfonamide/Thiourea Ligands as Potential Leishmanicidal Agents.

Leishmaniasis is a group of parasitic diseases with the potential to infect more than 1 billion people; however, its treatment is still old and inadequate. In order to contribute to changing this view, this work consisted of the development of complexes derived from MI metal ions with thioureas, aiming to obtain potential leishmanicidal agents. The thiourea ligands (HLR) were obtained by reactions of p-toluenesulfohydrazide with R-isothiocyanates and were used in complexation reactions with AgI and AuI, leading to the formation of complexes of composition [M(HLR)2]X (M = Ag or Au; X = NO3- or Cl-). All compounds were characterized by FTIR, 1H NMR, UV-vis, emission spectroscopy and elemental analysis. Some representatives were additionally studied by ESI-MS and single-crystal XRD. Their properties were further analyzed by DFT calculations. Their cytotoxicity on Vero cells and the extracellular leishmanicidal activity on Leishmania infantum and Leishmania braziliensis cells were evaluated. Additionally, the interaction of the complexes with the Old Yellow enzyme of the L. braziliensis (LbOYE) was examined. The biological tests showed that some compounds present remarkable leishmanicidal activity, even higher than that of the standard drug Glucantime, with different selectivity for the two species of Leishmania. Finally, the interaction studies with LbOYE revealed that this enzyme could be one of their biological targets.

DFT Studies of Dimethylaminophenyl-Substituted Phthalocyanine and Its Silver Complexes.

The dimethylaminophenyl-substituted silver phthalocyanine [dmaphPcAg] can be used as a UV-vis photoinitiator for in situ preparation of a silver/polymer nanocomposite. To verify early steps of the supposed mechanism of radical polymerization, we performed quantum chemical calculations of m[dmaphPcAg]q complexes with charges q = +1 to -2 in the two lowest spin states m, of a free ligand and its dehydrogenated/deprotonated products m[dmaphPcHn]q, n = 2 to 0, q = 0, -1 or -2, in the lowest spin states m. The calculated electronic structures and electron transitions of all the optimized structures in CHCl3 solutions are compared with experimental EPR and UV-vis spectra, respectively. The unstable 3[dmaphPcAg]+ species deduced only from previous EPR spin trap experiments was identified. In addition to 2[dmaphPcAg]0, our results suggest the coexistence of both reaction intermediates 1[dmaphPcAg]- and 3[dmaphPcAg]- in reaction solutions. Silver nanoparticle formation is a weak point of the supposed reaction mechanism from the energetic, stereochemistry, and electronic structure points of view.

Structure and Thermal Properties of Silver Complexes with 2,2′-Bipyridine and Fluorinated β-Diketonate Ligands

Structure and Thermal Properties of Silver Complexes with 2,2′-Bipyridine and Fluorinated β-Diketonate Ligands

Investigating the Catalytic Efficiency of Supported NHC‐Ag(I) Complexes in the Borono‐Minisci Reaction

AbstractA series of supported N‐heterocyclic carbene silver complexes (NHC‐Ag(I)) were prepared and characterized as catalysts for the borono‐Minisci reaction. After characterization, the synthesized catalysts were evaluated in batch mode to determine the reaction performance and kinetics. Interestingly, cyclic voltammetric analysis showed that the structure of both the complex and the ligand significantly influences the Ag(I)/Ag(II) redox potential and, in turn, the catalytic efficiency. Among the tested catalysts, the Si‐supported NHC‐Ag(I) 6 afforded the desired products in good to excellent yields in only 15 min, providing a complementary tactic to standard homogeneous approaches.

COMPLEXATION OF SILVER (I) C 2-ETHYLIMIDAZOLE

The acid-base properties of 2-ethylimidazole were studied by pH-metric titration (EM). Using the literature data and our own results, a number of changes in the acid-base properties (pКa) of imidazoles have been established: ethylimidazole (7,93)> imidazole (7.05)>2-phenylimidazole (6,48)>2-aminobenzimidazole (6,11)> benzimidazole (5,53)>2-phenylbenzimidazole (5,23)>2-mercaptoimidazole (2,97)>1-methyl-2-mercaptoimidazole (2,11). Method The process of complexation of silver(I) with 2-ethylimidazole in the temperature range of 273-318K was investigated using potentiometric titration using a silver electrode. It has been established that the increase in temperature does not affect the stoichiometric composition of complex particles formed in the Ag-EM-H2O system. The results obtained show that as the temperature increases, the stability constants decrease. On the basis of diagrams, the distribution of complex particles depending on the ligand concentration is shown that in System Ag-EM-H2O is mainly dominated by the bis-substituted complex, the yield of which at EM concentrations above 1·10-2 mol/l is 100%. The thermodynamic functions of the formation of 2-ethylimidazole silver complexes have been calculated. It has been established that complexation reactions are exothermic. Spontaneous occurrence of complexation reactions in the system Ag-EM-H2O contributes to a negative change in enthalpy.

Synthesis and catalytic activity of silver N-heterocyclic carbene complexes based on bis(3,5-dimethylpyrazol-1-yl)methyl-substituted pyridylimidazole

A series of N-heterocyclic carbene (NHC) silver complexes derived from 6-[bis(3,5-dimethylpyrazol-1-yl)methyl]-2-pyridylimidazole have been synthesized and characterized by physico-chemical and spectroscopic methods, and the structures of four complexes have been confirmed by X-ray structural analyses. The functionalized NHC is a monodentate ligand in (NHC)AgCl through the carbene carbon atom, and a bridging [C,N,N] tridentate ligand in (NHC)2Ag2(BF4)2 and (NHC)2Ag2(PF6)2 through two pyrazolyl nitrogens and the carbene carbon to form a metallomacrocycle, in which a head (carbene)– to tail (nitrogen) coordination mode to two silver atoms is observed. Preliminary catalytic tests show that these newly synthesized Ag–NHC complexes exhibit excellent catalytic activity at a low catalyst loading (0.1–1 mol%) in the aldehyde–amine–alkyne coupling reaction.

Paraptotic Cell Death as an Unprecedented Mode of Action Observed for New Bipyridine-Silver(I) Compounds Bearing Phosphane Coligands.

In this work, we investigated the anticancer activity of several novel silver(I) 2,2'-bipyridine complexes containing either triphenylphosphane (PPh3) or 1,2-bis(diphenylphosphino)ethane (dppe) ligands. All compounds were characterized by diverse analytical methods including ESI-MS spectrometry; NMR, UV-vis, and FTIR spectroscopies; and elemental analysis. Moreover, several compounds were also studied by X-ray single-crystal diffraction. Subsequently, the compounds were investigated for their anticancer activity against drug-resistant and -sensitive cancer cells. Noteworthily, neither carboplatin and oxaliplatin resistance nor p53 deletion impacted on their anticancer efficacy. MES-OV cells displayed exceptional hypersensitivity to the dppe-containing drugs. This effect was not based on thioredoxin reductase inhibition, enhanced drug uptake, or apoptosis induction. In contrast, dppe silver drugs induced paraptosis, a novel recently described form of programmed cell death. Together with the good tumor specificity of this compound's class, this work suggests that dppe-containing silver complexes could be interesting drug candidates for the treatment of resistant ovarian cancer.

Silver and Gold Complexes with NHC-Ligands Derived from Caffeine: Catalytic and Pharmacological Activity.

N-heterocyclic carbene (NHC) silver(I) and gold(I) complexes have found different applications in various research fields, as in medicinal chemistry for their antiproliferative, anticancer, and antibacterial activity, and in chemistry as innovative and effective catalysts. The possibility of modulating the physicochemical properties, by acting on their ligands and substituents, makes them versatile tools for the development of novel metal-based compounds, mostly as anticancer compounds. As it is known, chemotherapy is commonly adopted for the clinical treatment of different cancers, even though its efficacy is hampered by several factors. Thus, the development of more effective and less toxic drugs is still an urgent need. Herein, we reported the synthesis and characterization of new silver(I) and gold(I) complexes stabilized by caffeine-derived NHC ligands, together with their biological and catalytic activities. Our data highlight the interesting properties of this series as effective catalysts in A3-coupling and hydroamination reactions and as promising anticancer, anti-inflammatory, and antioxidant agents. The ability of these complexes in regulating different pathological aspects, and often co-promoting causes, of cancer makes them ideal leads to be further structurally functionalized and investigated.

Sythesis, characterisation, anticancer and antimicrobial activity of Ag-N-heterocyclic carbene complexes containing benzimidazole derivatives

To prepare a novel series of silver(I) complexes, the interaction of benzimidazolium salts having their two nitrogen atoms substituted by bulky groups with Ag2O in DCM has been carried out. Their structures were characterized by elemental analyses, 1H NMR, 13C NMR, elemental analysis, and IR spectroscopy techniques. Further, the antimicrobial and antifungal activities properties of both the salts and their silver(I)–NHC complexes were tested against positive and negative bacteria using the Clinical and Laboratory Standards Institute (CLSI) and the European Committee for Antimicrobial Susceptibility Testing (EUCAST) respectively. The results show that silver complexes are effective against E. coli, P. aeruginosa and S. aureus bacterial species with moderate to high activity, and their minimum inhibitory concentrations ranging from 25 to 400 µg/Ml. It was also observed that 3b compound, which has the best antifungal properties among the synthesized compounds, showed high antimicrobial activity when all bacterial species were taken into account. In addition, the salts and complexes were then evaluated for their ability to inhibit the proliferation of four different cancer cell lines (A549, MCF-7, HCT116, SH-SY5Y and BEAS-2B cells lines). AlamarBlue assay demonstrated that the salts and complexes exhibited potent cytotoxicity towards all cancer lines. 2c compound showed the highest cytotoxic activity against BEAS-2B, A549 and MCF-7 cell lines. Except for 2c, compounds 3d, 3e and 3f showed cytotoxic activity at the lowest concentrations against MCF7 cell line.The study highlights the importance of N-heterocyclic carbene ligands in the development of silver-based drugs with anticancer properties.

Manganese(II), copper(II) and silver(I) complexes containing 1,10-phenanthroline/1,10-phenanthroline-5,6-dione against Candida species.

Background: New chemotherapeutics are urgently required to treat Candida infections caused by drug-resistant strains. Methods: The effects of 16 1,10-phenanthroline (phen)/1,10-phenanthroline-5,6-dione/dicarboxylate complexed with Mn(II), Cu(II) and Ag(I) were evaluated against ten different Candida species. Results: Proliferation of Candida albicans, Candida dubliniensis, Candida famata, Candida glabrata, Candida guilliermondii, Candida kefyr, Candida krusei, Candida lusitaniae, Candida parapsilosis and Candida tropicalis was inhibited by three of six Cu(II) (MICs 1.52-21.55μM), three of three Ag(I) (MICs 0.11-12.74μM) and seven of seven Mn(II) (MICs 0.40-38.06μM) complexes. Among these [Mn2(oda)(phen)4(H2O)2][Mn2(oda)(phen)4(oda)2].4H2O, where oda=octanedioic acid, exhibited effective growth inhibition (MICs 0.4-3.25μM), favorable activity indexes, low toxicity against Vero cells and good/excellent selectivity indexes (46.88-375). Conclusion: [Mn2(oda)(phen)4(H2O)2][Mn2(oda)(phen)4(oda)2].4H2O represents a promising chemotherapeutic option for emerging, medically relevant and drug-resistant Candida species.

MODELLING OF SILVER CLUSTER COMPLEXES WITH ANTIBACTERIAL MEDICATION DIOXIDINE

By the method of the electron density functional in the variant DFT/B3L-YP5 the structures of small silver clusters (Agn, n = 1-3, 13) and their molecular complexes with antibacterial medication dioxidine (Dx) were calculated. The features in the geometric structure and energy of the interaction “metal cluster - dioxidine ligand” depending on the size (nuclearity) of the metal cluster are considered. For small clusters (n = 1-3), the tendency of metal coordination to only one of the oxygen atoms of the ligand molecule was revealed. The most stable are the complexes of silver trimers Dx-Ag3 and the icosahedral cluster of silver Dx-Ag13. These complexes are coordinated by two oxygen atoms of the hydroxyl groups of the dioxydine molecule at once. The difference between the obtained optimized structures of the silver-dioxidine complexes and the previously studied silver complexes with hydroxide ligands, for which the hydrogen atom of the hydroxyl group of the ligand is displaced during interaction, is shown.

Silver(I) complexes with diorganochalcogen ligands of type (2-MeC6H4CH2)2E (E = S, Se). Synthesis, structure and antiproliferative activity

Silver(I) complexes of types [Ag(X){E(CH2C6H4Me-2)2}] [E = S, X = CF3SO3 (1), NO3 (2), ClO4 (3); E = Se, X = CF3SO3 (4), NO3 (5), ClO4 (6)] and [Ag(X){E(CH2C6H4Me-2)2}2] [X = CF3SO3, E = S (7), Se (8); X = ClO4, E = S (9), Se (10)] were prepared by reacting the diorganochalcogenides (2-MeC6H4CH2)2E [E = S (L1), Se (L2)] with the appropriate silver(I) salt in a 1:1 and a 2:1 molar ratio, respectively. The ligands and the Ag(I) complexes were characterized by multinuclear NMR spectroscopy (1H, 13C{1H}, 19F{1H}, 77Se{1H}, as appropriate), ESI+ mass spectrometry, elemental analysis and IR spectroscopy. The crystal and molecular structures of the ligand L1 and the complexes 2, 5, 7, 8 and 9 were determined by single-crystal X-ray diffraction. The molar conductivity of the reported metal complexes showed their behaviour as 1:1 electrolytes in solution, while in solid state the inorganic anionic ligand is coordinated to silver by OAg bonds. Preliminary results showed that the silver(I) complexes bearing triflato ligands have in vitro promising antiproliferative activity against the murine melanoma B16.F10 cells.

Metal Complexes Containing Homoleptic Diorganoselenium(II) Ligands: Synthesis, Characterization and Investigation of Optical Properties.

[(Z)-2'-{2-C6H5-(4H)-oxazol-5-one}CHC6H4]2Se (5, L1) and [(Z)-4'-{2-C6H5-(4H)-oxazol-5-one}CHC6H4]2Se (6, L2) were prepared, structurally characterized and used as ligands to obtain new metal complexes of types [MX(Ln)] [L1: M = Ag, X = OTf (7); M = Au, X = Cl (13); L2: M = Ag, X = OTf (8); M = Au, X = Cl (14)], [(MX)2(Ln)] [M = Ag, X = OTf, L1 (9); L2 (10)], [ZnCl2(Ln)] [L1 (15); L2 (16)] and [Ag(Ln)][PF6] [L1 (11); L2 (12)]. The silver complexes 7 and 8 were ionic species (1:1 electrolytes) in a MeCN solution, while in the solid state, the triflate fragments were bonded to the silver cations. Similarly, the 2:1 complexes 9 and 10 were found to behave as 1:2 electrolytes in a MeCN solution, but single-crystal X-ray diffraction demonstrated that compound 9 showed the formation of a dimer in the solid state: a tetranuclear [Ag(OTf)]4 built through bridging triflate ligands was coordinated by two bridging organoselenium ligands through the nitrogen from the oxazolone ring and the selenium atoms in a 1κN:2κSe fashion. Supramolecular architectures supported by intermolecular C-H∙∙∙π, C-H∙∙∙O, Cl∙∙∙H and F∙∙∙H interactions were observed in compounds 4, 5 and 9. The compounds exhibited similar photophysical properties, with a bathochromic shift in the UV-Vis spectra caused by the position of the oxazolone ring on the phenyl ring attached to the selenium atoms.

A Brief Review on Silver Complexes of Functionalized N-heterocyclic Carbene Ligand

A Brief Review on Silver Complexes of Functionalized N-heterocyclic Carbene Ligand

Synthesis and characterization of new palladium (II) and silver (I) thiosemicarbazone derived by acenaphthenequinone complexes and their antimicrobial activity

The ability of substituted acenaphthenequinone-thiosemicarbazones to do complexation with Pd(II) and Ag(I) salts was investigated. The obtained Pd(II) 5a-f and Ag(I) 7a-f complexes showed that ligation was occurred during the reaction of two equivalents of the ligands with one equivalent of the metal salts. In case of Pd complexes 5a-f, two moles of HCl were eliminated during complexation process. Whereas direct ligation was occurred during complexation of one mole of AgNO3 and two moles of ligands to form the corresponding cationic-anionic salts 7a-f. IR, NMR, and UV–vis spectra were used to deduce the structure of the formed metal complexes. X-ray structure analysis proved the syn-form of bis(bidentate) structure of Pd complex 5e, as Pd showed a square planar coordination with two sulfur and two nitrogen atoms. The cationic-anionic nature of silver complexes was revealed by molar conductance. UV–visible spectra were also investigated by means of Time-Dependent Density-Functional Theory (TD-DFT) computations. The obtained metal complexes were also investigated asantibacterial and antifungal agents. Compounds 5f, 5e, 7d, and 7f were found to be the most active and effective against the four bacterial strains, with compound 7f having the most potent action. Compound 7f (R = 3-OMe-Ph) showed MIC values of 0.066, 0.018, 0.018, and 0.033 µg/mL against B. subtilis, S. aureus, E. coli, and K. pneumoniae, respectively. For compound 7d (R = Benzyl), the MIC values are found as 0.028, 0.057, 0.028, and 0.028 µg/mL against the same previous bacterial strains. Compounds 5d, 5e, 7c, and 7f demonstrated promising antifungal activity against C. albicans with MIC values of 0.029, 0.023, 0.018, and 0.027 µg/ml, respectively, when compared to the reference fluconazole, which had a MIC value of 0.020 µg/ml. Compound 7f revealed inhibitory activity of E. coli DNA gyrase (IC50 = 210 ± 15 nM, respectively) being 1.2-folds less potent than the reference novobiocin (IC50 = 170 ± 20 nM).