The iron(III) and nickel(II) complexes with tetradentate thiosemicarbazones. Synthesis, experimental, theoretical characterization, and antiviral effect against SARS-CoV-2

A multi-technique approach to enlighten the role of metal coordination in calcitermin antiviral properties

In this work we presented how the use of suitable electroanalytical, thermodynamic and spectroscopic methods combined with proper experimental conditions can provide comprehensive information on the interaction between metal ions and peptides in solution, as a successful strategy for studying biological systems. Our candidate peptide is calcitermin, an effective metal chelator with significant anti-Candida and antibacterial activity in the presence of divalent metals. While the bioinorganic chemistry of calcitermin with zinc and copper is quite well described in the literature, no data about nickel complexes are available; we therefore deepened calcitermin ability to form nickel complexes by different analytical techniques, including potentiometry, ultraviolet-visible absorption spectrophotometry, circular dichroism and high-resolution mass spectrometry. Moreover, for the first time we have investigated the antiviral activity of calcitermin and its metal complexes towards Herpes simplex type 1. Despite the nickel-associated slow kinetics, which requires specific experimental precautions, calcitermin forms stable complexes with this cation at different pH conditions. Both the apopeptide and its metal complexes show a random coil secondary structure, which is often characteristic of viral cellular adhesion inhibition. This research highlights that calcitermin and its metal complexes can interfere with viral infections, particularly HSV-1, most likely by altering cell membrane permeability.

RuIII-Morpholine-Derived Thiosemicarbazone-Based Metallodrugs: Lysosome-Targeted Anticancer Agents

The idea of coordinating biologically active ligand systems to metal centers to exploit their synergistic effects has gained momentum. Therefore, in this report, three RuIII complexes 1-3 of morpholine-derived thiosemicarbazone ligands have been prepared and characterized by spectroscopy and HRMS along with the structure of 2 through a single-crystal X-ray diffraction study. The solution stability of 1-3 was tested using conventional techniques such as UV-vis and HRMS. Further, the anticancer activity of 1-3 was tested in HT-29 and HeLa cancer cell lines. To gain insight into their mechanism of action, the cytotoxicity, hydrophobicity, and the interaction of 1-3 with DNA and HSA were evaluated by different conventional methods such as absorption, fluorescence, and circular dichroism studies. Along with favorable biomolecule interaction, 1-3 revealed potent selectivity toward cancer cells, which is a prerequisite for the generation of an anticancer drug. According to cell viability results, 1 has the highest cytotoxicity among all in the group, against both cells, respectively. Additionally, the fluorescence-active ruthenium complexes selectively target lysosomes, which is evaluated by live-cell imaging. 1-3 disrupt the lysosome membrane potential by generating an excessive amount of reactive oxygen species, which results in an apoptotic mode of cell death.

Copper(II) complexes of 2-hydroxy-1-naphthaldehyde Schiff bases: synthesis, in vitro activity and computational studies

BACKGROUND

Due to the divers biological applications of Cu(II) complexes, we in this study reports the various Cu(II) complexes. The study aims to synthesize and assess new Cu(II) complexes as powerful β-glucuronidase inhibitors.

METHODS

Five Schiff base ligands and their complexes were synthesized, characterized, and screened against β-glucuronidase inhibitory activity.

RESULTS

In the series, compounds 3e, 3c, 2b, and 2c ascribed powerful inhibition ranging from (IC50  = 3.0 ± 0.7 µM) to (IC50  = 19.2 ± 0.8 µM). A precise and particular arrangement of atoms is suggested by the triclinic p-1 space group and the existence of a single molecule in an asymmetric unit, which are indispensable for the reactivity as well as the stability of the compounds. The analysis of the Hirshfeld surface provides information about the hydrogen intermolecular and π-π interactions. Based on molecular docking, binding potency increasing by complexation 3a-e compared to ligands 2a-e as well as reference Saccharic acid and uronic isofagomine inhibitor, suggesting that it may be a potent inhibitor of these receptors.

CONCLUSION

The work recognizes latent active compounds for novel β-glucoronidase inhibitors, by further support these may be harnessed for the development of potent drugs.

Novel α-N-heterocyclic thiosemicarbazone complexes: synthesis, characterization, and antimicrobial of properties investigation

In this paper, eight novel α-N-heterocyclic thiosemicarbazone complexes were synthesized in search of new biologically active compounds, and characterized via organic elemental analysis, nuclear magnetic resonance spectroscopy, infrared spectra, thermogravimetric analysis, ultraviolet-visible spectroscopy, molar conductance and magnetic susceptibility measurements. The in vitro antimicrobial activity of these complexes was examined against ten disease-causing pathogens: Gram-positive bacteria (Micrococcus luteus ATCC9341, Staphylococcus epidermidis ATCC12228, Bacillus cereus RSKK863) and Gram-negative bacteria (Pseudomonas aeroginosa ATCC27853, Klebsiella pneumonia ATCC27853, Enterobacter aerogenes ATCC51342, Salmonella typhi H NCTC9018394, Shigella dysenteria NCTC2966, Proteus vulgaris RSKK96026) and yeast (Candida albicans Y-1200-NIH). The results revealed that the α-N-heterocyclic thiosemicarbazone compounds showed potent activity. It was observed that all thiosemicarbazone complexes were more susceptible to Gram-negative strains based on the presence of an electron-withdrawing substituent (-Br/-Cl/-F). It was determined that thiosemicarbazone Cu2+complexes showed stronger antifungal effects.

In Vitro and In Silico Studies on 4-Nitroacetophenone Thiosemicarbazone Potential Cytotoxicity Against A549 Cell Lines

Lung malignancy is a major worldwide issue that occurs due to the dysregulation of various growth factors. Lung cancer has no apparent signs in the early stages, which makes it harder to catch it in time and leads to a higher fatality rate. So, the goal of this work was to create and analyze a novel chemical molecule called 4-nitro acetophenone thiosemicarbazone (4-NAPTSc) against the lung cancer cell line A549 and human non-tumorigenic lung epithelial cell line BAES-2B. The ligand was synthesized by refluxing the reaction mixture of 4-nitro acetophenone and thiosemicarbazide and was further characterized by UV, FTIR, and 1H and 13C NMR and Differential Scanning Calorimetry (DSC) study. Cytotoxicity assay/MTT (3-(4,5-dimethylthiazol-2-yl))2,5-diphenyltetrazolium bromide) was used to evaluate the cytotoxicity of the compound. Epidermal growth factor receptors (EGFR), polo-like kinase-1 (PLK1), and vascular endothelial growth factor receptors (VEGFR) were chosen as the target proteins for molecular docking to find potential ligand binding sites and inhibit their function. A novel yellow-colored crystalline solid has been synthesized. 4-NAPTSc had an IC50 of 2.93 μg/mL against the A549 lung cancer cells. When the dosage is increased from 5 to 15 μg/mL along with time, the cell viability falls. Docking results showed that the compound binds with the targeted proteins' amino acid residues, and the likeness profile of the compound is also favorable. This study reveals that the compound has the potential for further investigation and can be used in multitargeted cancer therapies.

Can iron chelators ameliorate viral infections?

The redox reactivity of iron is a double-edged sword for cell functions, being either essential or harmful depending on metal concentration and location. Deregulation of iron homeostasis is associated with several clinical conditions, including viral infections. Clinical studies as well as in silico, in vitro and in vivo models show direct effects of several viruses on iron levels. There is support for the strategy of iron chelation as an alternative therapy to inhibit infection and/or viral replication, on the rationale that iron is required for the synthesis of some viral proteins and genes. In addition, abnormal iron levels can affect signaling immune response. However, other studies report different effects of viral infections on iron homeostasis, depending on the class and genotype of the virus, therefore making it difficult to predict whether iron chelation would have any benefit. This review brings general aspects of the relationship between iron homeostasis and the nonspecific immune response to viral infections, along with its relevance to the progress or inhibition of the inflammatory process, in order to elucidate situations in which the use of iron chelators could be efficient as antivirals.

Unusual Ni⋯Ni interaction in Ni(ii) complexes as potential inhibitors for the development of new anti-SARS-CoV-2 Omicron drugs

Two nickel(ii) coordination complexes [Ni(L)]2(1) and [Ni(L)]n(2) of a tetradentate Schiff base ligand (H2L) derived from 2-hydroxy-1-naphthaldehyde with ethylenediamine were synthesized, designed, and characterized via spectroscopic and single crystal XRD analyses. Both nickel(ii) complexes exhibited unusual Ni⋯Ni interactions and were fully characterized via single-crystal X-ray crystallography. Nickel(ii) complexes [Ni(L)]2(1) and [Ni(L)]n(2) crystallize in monoclinic and triclinic crystal systems with P21/c and P1̄ space groups, respectively, and revealed square planar geometry around each Ni(ii) ion. The structure of both the complexes have established the existence of a new kind of metal system containing nickel(ii)-nickel(ii) interactions with a square planar-like geometry about the nickel(ii) atoms. Both square planar Ni(ii) complexes were often stacked with relatively short Ni⋯Ni distances. The non-bonded Ni-Ni distance (Ni⋯Ni separation) seems to be 3.356 Å and 3.214 Å from the nickel atoms of [Ni(L)]2(1) and [Ni(L)]n(2), respectively. These distances are shorter than the sum of their van der Waals radii (4.80 Å) but longer than the sum of their covalent radii (2.50 Å), indicating that there is a Ni⋯Ni interaction but not a Ni-Ni bond. The discrete molecules are π-stacked and connected via weak intermolecular interactions (C-H⋯O and C-H⋯N). Cyclic voltammetry measurements were obtained for both the complexes, and their pharmacokinetic and chemoinformatics properties were also explored. Detailed structural analysis and non-covalent supramolecular interactions were investigated using single-crystal structure analysis and computational approaches. Both the unique structures show good inhibition performance for the Omicron spike proteins of the SARS CoV-2 virus. To gain insights into potential SARS-CoV-2 Omicron drugs and find inhibitors against the Omicron variants of SARS-CoV-2, we examined the molecular docking of the nickel(ii) complexes [Ni(L)]2(1) and [Ni(L)]n(2) with the SARS-CoV-2 Omicron spike protein (PDB ID: 7WK2 and 7WVO). A strong binding was predicted between Ni(ii) coordination complexes [Ni(L)]2(1) and [Ni(L)]n(2) with the SARS-CoV-2 Omicron variant receptor protein through the negative value of binding affinity. Molecular docking of Nil(ii) complexes [Ni(L)]2(1) and [Ni(L)]n(2) with a DNA duplex (PDB ID: 7D3T) and RNA (PDB ID: 7TDC) binding protein was also studied. Overall, this study suggests that Ni(ii) complexes can be considered as drug candidates against the Omicron variants of SARS-CoV-2.

Antiproliferative Activity and DNA Interaction Studies of a Series of N4,N4-Dimethylated Thiosemicarbazone Derivatives

The exploitation of bioactive natural sources to obtain new anticancer agents with novel modes of action may represent an innovative and successful strategy in the field of medicinal chemistry. Many natural products and their chemical analogues have been proposed as starting molecules to synthesise compounds with increased biological potential. In this work, the design, synthesis, and characterisation of a new series of N4,N4-dimethylated thiosemicarbazone Cu(II), Ni(II), and Pt(II) complexes are reported and investigated for their in vitro toxicological profile against a leukaemia cell line (U937). The antiproliferative activity was studied by MTS assay to determine the GI50 value for each compound after 24 h of treatment, while the genotoxic potential was investigated to determine if the complexes could cause DNA damage. In addition, the interaction between the synthesised molecules and DNA was explored by means of spectroscopic techniques, showing that for Pt and Ni derivatives a single mode of action can be postulated, while the Cu analogue behaves differently.

New nickel(ii) Schiff base complexes as potential tools against SARS-CoV-2 Omicron target proteins: an in silico approach

Herein, we report the in silico design and synthesis of two new nickel(ii) coordination complexes, based on Schiff bases derived from the 2-hydroxy-1-naphthaldehyde moiety.

Bioinformatics and systems biology approaches to identify molecular targeting mechanism influenced by COVID-19 on heart failure

Coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged as a contemporary hazard to people. It has been known that COVID-19 can both induce heart failure (HF) and raise the risk of patient mortality. However, the mechanism underlying the association between COVID-19 and HF remains unclear. The common molecular pathways between COVID-19 and HF were identified using bioinformatic and systems biology techniques. Transcriptome analysis was performed to identify differentially expressed genes (DEGs). To identify gene ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways, common DEGs were used for enrichment analysis. The results showed that COVID-19 and HF have several common immune mechanisms, including differentiation of T helper (Th) 1, Th 2, Th 17 cells; activation of lymphocytes; and binding of major histocompatibility complex class I and II protein complexes. Furthermore, a protein-protein interaction network was constructed to identify hub genes, and immune cell infiltration analysis was performed. Six hub genes (FCGR3A, CD69, IFNG, CCR7, CCL5, and CCL4) were closely associated with COVID-19 and HF. These targets were associated with immune cells (central memory CD8 T cells, T follicular helper cells, regulatory T cells, myeloid-derived suppressor cells, plasmacytoid dendritic cells, macrophages, eosinophils, and neutrophils). Additionally, transcription factors, microRNAs, drugs, and chemicals that are closely associated with COVID-19 and HF were identified through the interaction network.

Synthesis, characterization, and biological activities of zinc(II), copper(II) and nickel(II) complexes of an aminoquinoline derivative

Interest is increasingly focused on the use of transition metal complexes as biochemical, medical, analytical, pharmaceutical, agronomic, anticancer, and antibacterial agents. In this study, three complexes of [Zn(H2L)Cl] (1), [Cu(H2L)(H2O)(NO3)] (2) and [Ni(H2L)(NO3)].2H2O (3) were synthesized from a 2-chloroquinoline-3-carbaldehyde derived ligand [H3L = ((E)-2-(((2-((2-hydroxyethyl)amino)quinolin-3-yl)methylene)amino)ethanol. The compounds were characterized using physicochemical and spectroscopic methods. The results demonstrate that the free ligand behaves as a tridentate ligand with one oxygen and two nitrogen (ONN) donor atoms in 1:1 metal:ligand ratio. The formation constants of the complexes were found to be (KZn(II) = 2.3 × 106, KCu(II) = 2.9 × 106, and KNi(II) = 3.8 × 105). The thermodynamic parameters indicated that the reactions were spontaneous with exothermic nature of metal-ligand interaction energies. Based on the analyses of the experimental (EDX, FTIR, PXRD, MS and TGA) and DFT results, a distorted tetrahedral, a distorted square pyramidal and square planar geometry for Zn(II), Cu(II) and Ni(II) complexes, respectively, were proposed. The B3LYP calculated IR frequencies and TD-B3LYP calculated absorption spectra were found to be in good agreement with the corresponding experimental results. The powder XRD data confirmed that the Zn(II), Cu(II) and Ni(II) complexes have polycrystalline nature with average crystallite sizes of 27.86, 33.54, 37.40 Å, respectively. In vitro antibacterial activity analyses of the complexes were studied with disk diffusion method, in which the complexes showed better activity than the precursor ligand. Particularly the Cu(II) complex showed higher percent activity index (62, 90%), than both Zn(II) (54, 82%) and Ni(II) (41, 68%) complexes against both E. coli and P. aeruginosa, respectively. Using the DPPH assay, the complexes were further assessed for their antioxidant capacities. All metal complexes showed improved antioxidant activity than the free ligand. Zn(II) and Cu(II) complexes, which had IC50 values of 10.46 and 8.62 μg/ml, respectively, showed the best antioxidant activity. The calculated results of Lipinski’s rule of five also showed that the target complexes have drug-like molecular nature and similarly, the results of binding mode of action of these compounds against E. coli DNA gyrase B and P. aeruginosa LasR.DNA were found to be in good agreement with the in vitro biological activities.

Novel Zinc(II) and Copper(II) Complexes of 2-((2-Hydroxyethyl)amino)quinoline-3-carbaldehyde for Antibacterial and Antioxidant Activities: A Combined Experimental, DFT, and Docking Studies

In the present work, two novel complexes of zinc(II) and copper(II) were synthesized from the ligand 2-((2-hydroxyethyl)amino)quinoline-3-carbaldehyde (H ₂ L) in a 1:2 metal-to-ligand ratio in methanol. The complexes were characterized by UV-visible spectroscopy, fluorescence spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX), mass spectrometry (MS), nuclear magnetic resonance (NMR) spectroscopy, and thermogravimetric analysis (TGA) experimental techniques and density functional theory (DFT) calculations. The spectral data revealed that the mono-deprotonated (HL) ligand acted as a bidentate ligand, which bound to both Zn(II) and Cu(II) ions via the nitrogen atom of the amine (N-H) and the hydroxyl (O-H) groups through the deprotonated oxygen atom. Formation constants and thermal analysis indicated that both metal complexes are stable up to 100 °C with thermodynamically favored chemical reactions. The Cu(II) complex showed antibacterial activities with the zones of inhibition of 20.90 ± 2.00 mm against Pseudomonas aeruginosa, 19.69 ± 0.71 mm against Staphylococcus aureus, and 18.58 ± 1.04 mm against Streptococcus pyogenes. These results are relatively higher compared with the Zn(II) complex at the same concentration. The minimum inhibitory concentration (MIC) results for the complexes also showed similar trends against the three bacteria. On the other hand, radical scavenging activities of both Cu(II) and Zn(II) complexes showed half-maximal inhibitory concentrations (IC₅₀) of 4.72 and 8.2 μg/mL, respectively, while ascorbic acid (a positive control) has a value of 4.28 μg/mL. The Cu(II) complex exhibited better communication with the positive control, indicating its potential use for biological activities. The calculated and in silico molecular docking results also strongly support the experimental results.

Synthesis and characterization of violurate - based Mn(II) and Cu(II) complexes nano-crystallites as DNA-binders and therapeutics agents against SARS-CoV-2 virus

Synthesis and structural characterization of nano crystallites of bis-violurate-based manganese(II) and copper(II) chelates is the subject of the present study. Analytical data and mass spectra as well as thermal analysis determined the molecular formulas of the present metal chelates. Spectroscopic and magnetic measurements assigned the structural formula of the present violurate metal complexes. The spectroscopic and magnetic investigations along with structural analysis results indicated the square planar geometry of both the Mn(II) and Cu(II) complexes. The structural analysis of the synthesized metal complexes was achieved by processing the PXRD data using specialized software Expo 2014. Spectrophotometeric and viscosity measurements showed that violuric acid and its Mn(II) and Cu(II) complexes successfully bind to DNA with intrinsic binding constants K_b from 38.2 × 10⁵ to 26.4 × 10⁶ M⁻¹. The antiviral activity study displayed that the inhibitory concentrations (IC₅₀) of SARS-CoV-2 by violuric acid and its Mn(II) and Cu(II) complexes are 84.01, 39.58 and 44.86 μM respectively. Molecular docking calculations were performed on the SARS-CoV-2 virus protein and the computed binding energy values are −0.8, −3.860 −5.187 and −4.790, kcal/mol for the native ligand, violuric acid and its Mn(II) and Cu(II) complexes respectively. Insights into the relationship between structures of the current compounds and their degree of reactivity are discussed.

An Iron(III)-S-methylthiosemicarbazone Complex: Synthesis, Spectral Characterization, and Antioxidant Potency Measured by CUPRAC and DPPH Methods

An iron(III) complex, [Fe(L1)Cl].H2O, was synthesized by template condensation reaction of 1,1,1-Trifluoroacetylacetone-S-methylthiosemicarbazone hydrogen iodide (L) and 2,3-dihydroxybenzaldehyde in the presence of iron(III) ions. The complex was characterized by IR, ESI MS and X-ray diffraction techniques. Free radical scavenging (FRS) ability and antioxidant capacity of the S-methylthiosemicarbazone and the iron(III) complex were evaluated through DPPH and CUPRAC methods, respectively. The complex exerted better than the S-methylthiosemicarbazone in both TEAC and FRS% values. In addition, iron(III) complex was found to be 3.1 times more antioxidant than the reference ascorbic acid according to the CUPRAC method.

Hydroxamate and thiosemicarbazone: Two highly promising scaffolds for the development of SARS-CoV-2 antivirals

The emerging COVID-19 pandemic generated by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has severely threatened human health. The main protease (Mpro) of SARS-CoV-2 is promising target for antiviral drugs, which plays a vital role for viral duplication. Development of the inhibitor against Mpro is an ideal strategy to combat COVID-19. In this work, twenty-three hydroxamates 1a-i and thiosemicarbazones 2a-n were identified by FRET screening to be the potent inhibitors of Mpro, which exhibited more than 94% (except 1c) and more than 69% inhibition, and an IC50 value in the range of 0.12-31.51 and 2.43-34.22 μM, respectively. 1a and 2b were found to be the most effective inhibitors in the hydroxamates and thiosemicarbazones, with an IC50 of 0.12 and 2.43 μM, respectively. Enzyme kinetics, jump dilution and thermal shift assays revealed that 2b is a competitive inhibitor of Mpro, while 1a is a time-dependently inhibitor; 2b reversibly but 1a irreversibly bound to the target; the binding of 2b increased but 1a decreased stability of the target, and DTT assays indicate that 1a is the promiscuous cysteine protease inhibitor. Cytotoxicity assays showed that 1a has low, but 2b has certain cytotoxicity on the mouse fibroblast cells (L929). Docking studies revealed that the benzyloxycarbonyl carbon of 1a formed thioester with Cys145, while the phenolic hydroxyl oxygen of 2b formed H-bonds with Cys145 and Asn142. This work provided two promising scaffolds for the development of Mpro inhibitors to combat COVID-19.

Synthesis, characterization, thermal properties, antimicrobial evaluation, ADMET study, and molecular docking simulation of new mono Cu (II) and Zn (II) complexes with 2-oxoindole derivatives

One of the interesting research fields is developing and assessing novel metal-containing medications. A new isatin-3-thiosemicarbazone derivative 4 was synthesized by two different methods based on hydrazone derivatives 2 and 3. Additionally, the chelation of thiosemicarbazone with copper (II) and zinc (II) forms a monobasic tridentate (ONS) complex with two five-member rings and a tetrahedral geometry structure. The structure of synthesized complexes was characterized using elemental analysis, FT-IR, mass spectra, and ¹H/¹³C NMR. Thermogravimetric analysis revealed the upgrading of the thermal stability of metal complexes compared to their thiosemicarbazone ligand. The stoichiometric ratio of the coordination confirmed the formation of 1:1 (M: L) stoichiometry. In vitro antimicrobial activity was screened against two gram-positive, two gram-negative, and one fungal strain. Both ligand 4 and Zn complex 6 displayed high antimicrobial activity compared with copper complex 5 based on the zone of inhibition. Further, MIC and MBC were determined for both zinc and ligand. The zinc complex 6 displayed excellent antimicrobial activity with (MIC = 3.9-27.77 μg/mL) against bacterial strains and (MIC = 7.81 μg/mL) against C. albicans, as well as exhibited MBC values ranging between (MBC = 6.51-45.58 μg/mL) and (MFC = 13.58 μg/mL), respectively, and demonstrated bactericidal and fungicidal behavior. The in-silico ADMET study for ligand and two complexes were determined and showed non-AMES toxicity, non-carcinogenic, and obey the rule of five. A comparative docking study provided more insight into the binding mechanisms and suggested that antimicrobial activity may be due to inhibition of different targets.