Synthesis, structural and antimicrobial studies of type II topoisomerase-targeted copper(II) complexes of 1,3-disubstituted thiourea ligands

Copper and Copper Complexes in Tumor Therapy

Copper (Cu), a crucial trace element in physiological processes, has garnered significant interest for its involvement in cancer progression and potential therapeutic applications. The regulation of cellular copper levels is essential for maintaining copper homeostasis, as imbalances can lead to toxicity and cell death. The development of drugs that target copper homeostasis has emerged as a promising strategy for anticancer treatment, with a particular focus on copper chelators, copper ionophores, and novel copper complexes. Recent research has also investigated the potential of copper complexes in cancer therapy.

Recently Reported Biological Activities and Action Targets of Pt(II)- and Cu(II)-Based Complexes

Most diseases that affect human beings across the world are now treated with drugs of organic origin. However, some of these are associated with side effects, toxicity, and resistance phenomena. For the treatment of many illnesses, the development of new molecules with pharmacological potential is now an urgent matter. The biological activities of metal complexes have been reported to have antitumor, antimicrobial, anti-inflammatory, anti-infective and antiparasitic effects, amongst others. Metal complexes are effective because they possess unique properties. For example, the complex entity possesses the effective biological activity, then the formation of coordination bonds between the metal ions and ligands is controlled, metal ions provide it with extraordinary mechanisms of action because of characteristics such as d-orbitals, oxidation states, and specific orientations; metal complexes also exhibit good stability and good physicochemical properties such as water solubility. Platinum is a transition metal widely used in the design of drugs with antineoplastic activities; however, platinum is associated with side effects which have made it necessary to search for, and design, novel complexes based on other metals. Copper is a biometal which is found in living systems; it is now used in the design of metal complexes with biological activities that have demonstrated antitumoral, antimicrobial and anti-inflammatory effects, amongst others. In this review, we consider the open horizons of Cu(II)- and Pt(II)-based complexes, new trends in their design, their synthesis, their biological activities and their targets of action.

In vitro antimycobacterial activity and interaction profiles of diarylthiourea-copper (II) complexes with antitubercular drugs against Mycobacterium tuberculosis isolates

The activity of several halogenated copper (II) complexes of 4-chloro-3-nitrophenylthiourea derivatives has been tested against Mycobacterium tuberculosis strains and strains of non-tuberculous mycobacteria. The compounds were 2-16 times more potent than current TB-drugs against multidrug-resistant M. tuberculosis 210. The 3,4-dichlorophenylthiourea complex (5) was equipotent to ethambutol (EMB) towards M. tuberculosis H37Rv and 192 strains. All derivatives acted 2-8 times stronger than isoniazid (INH) against nontuberculous isolates. In the presence of chosen coordinates, the 2-64 times reduction of MIC values of standard drugs was denoted. The synergistic interaction was found between the complex 4 and rifampicin (RMP), and additivity of 1-5, 8 in pairs with EMB and/or streptomycin (SM) against M. tuberculosis 800 was established. All coordination compounds in combination with at least one drug showed additive activity towards both H37Rv and 192 isolates. In 67% incidences of indifference, the individual MIC of a drug decreased 2-16-fold. One can conclude that the novel thiourea chelates described here are potent hits for further developments of new agents against tuberculosis.

Molecular docking, synthesis, and antibacterial activity of the analogs of 1-allyl-3-benzoylthiourea

Background and purpose

The incidence of antibiotic resistance rapidly emerges over the globe. In the present study, the synthesis of thiourea derivatives as antibacterial agents and their biological evaluation are reported.

Experimental approach

Preliminary studies were done by molecular docking of four analogs of 1-allyl-3-benzoylthiourea, clorobiocin, and ciprofloxacin on the DNA gyrase subunit B receptor (PDB: 1KZN). The nucleophilic substitution reaction of benzoyl chloride analogs to the allylthiourea yielded four 1-allyl-3-benzoylthiourea analogs (Cpd 1-4). The reactions were done by a modified Schotten Baumann method. The in vitro antimicrobial activities were determined using the agar dilution method against methicillin-resistant Staphylococcus aureus (MRSA), Salmonella typhi, Escherichia coli, and Pseudomonas aeruginosa.

Findings/Results

The in-silico study showed that Cpd 1-4 possesses a good interaction on the DNA gyrase subunit B receptor compared to the ciprofloxacin. Cpd 3 had the best binding affinity with a rerank score of - 91.2304. Although the candidate compounds showed unsatisfactory antibacterial activity, they indicated an increasing trend of growth inhibition along with the increment of concentration. Cpd 1 and 4 exhibited in vitro antibacterial activities against MRSA with a minimum inhibitory concentration value of 1000 µg/mL, better compared to the other compounds.

Conclusion and implication

Despite lacking antibacterial activity, all the synthesized compounds showed an increased trend of growth inhibition along with the increment of concentration. Therefore, additional development should be implemented to the compounds of interest in which optimization of lipophilicity and steric properties are suggested.

Synthesis, Structural Characterization and Biological Activity Evaluation of Novel Cu(II) Complexes with 3-(trifluoromethyl)phenylthiourea Derivatives

Copper complexes with 1,3-disubstituted thiourea derivatives, all containing 3-(trifluoromethyl)phenyl tail and 1-alkyl/halogen-phenyl substituent, were synthesized. The experimental spectroscopic studies and theoretical calculation revealed that two ligands coordinate to Cu(II) in a bidentate fashion via thiocarbonyl S and deprotonated N atoms of thiourea moiety. Such monomers are characteristic of alkylphenylthiourea complexes, whereas the formation of a sandwich-type dimer is observed for halogeno derivatives. For the first time, the structural identifications of CuN₂S₂-based complexes using experimental and theoretical X-ray absorption near edge structure are demonstrated. The dimeric halogeno derivatives showed higher antimicrobial activity in comparison with alkylphenylthiourea complexes. The Cu(II) complex of 1-(4-chloro-3-nitrophenyl)-3-[3-(trifluoromethyl)phenyl]thiourea was active against 19 strains of methicillin-resistant Staphylococci (MIC = 2 µg/mL). This derivative acted as a dual inhibitor of DNA gyrase and topoisomerase IV isolated from Staphylococcus aureus. Additionally, complexes of halogenphenylthiourea strongly inhibited the growth of mycobacteria isolated from tuberculosis patients, even fourfold stronger than the reference isoniazid. The complexes exerted weak to moderate antitumor activity (towards SW480, SW620, and PC3) being non-toxic towards normal HaCaT cells.

Design, molecular docking, and molecular dynamics of thiourea-iron (III) metal complexes as NUDT5 inhibitors for breast cancer treatment

In research, anticancer agents, such as thiourea derivative compounds, and metal complexes, such as those complexed with iron (III) metal, are often studied. The metal complexes are presumably more active than thiourea derivatives as free ligands; some negative effects may be reduced. The computational studies used in this study involved molecular docking with AutoDock and molecular dynamics (MD) simulations using Desmond to evaluate the stability of the interactions. The docking and MD analysis results showed that compounds 2 and 6 had stable interactions with NUDIX hydrolase type 5 (NUDT5)—one of the therapeutic targets for breast cancer—where they had the lowest root mean square deviation (RMSD) and root mean square fluctuation (RMSF) values compared to the other compounds. Together, these compounds are anti-breast cancer drug candidates.

Metal Complexes—A Promising Approach to Target Biofilm Associated Infections

Microbial biofilms are represented by sessile microbial communities with modified gene expression and phenotype, adhered to a surface and embedded in a matrix of self-produced extracellular polymeric substances (EPS). Microbial biofilms can develop on both prosthetic devices and tissues, generating chronic and persistent infections that cannot be eradicated with classical organic-based antimicrobials, because of their increased tolerance to antimicrobials and the host immune system. Several complexes based mostly on 3D ions have shown promising potential for fighting biofilm-associated infections, due to their large spectrum antimicrobial and anti-biofilm activity. The literature usually reports species containing Mn(II), Ni(II), Co(II), Cu(II) or Zn(II) and a large variety of multidentate ligands with chelating properties such as antibiotics, Schiff bases, biguanides, N-based macrocyclic and fused rings derivatives. This review presents the progress in the development of such species and their anti-biofilm activity, as well as the contribution of biomaterials science to incorporate these complexes in composite platforms for reducing the negative impact of medical biofilms.

Investigation of the Mechanisms of Cytotoxic Activity of 1,3-Disubstituted Thiourea Derivatives

Substituted thiourea derivatives possess confirmed cytotoxic activity towards cancer but also normal cells. To develop new selective antitumor agents, a series of 3-(trifluoromethyl)phenylthiourea analogs were synthesized, and their cytotoxicity was evaluated in vitro against the cell line panel. Compounds 1-5, 8, and 9 were highly cytotoxic against human colon (SW480, SW620) and prostate (PC3) cancer cells, and leukemia K-562 cell lines (IC₅₀ ≤ 10 µM), with favorable selectivity over normal HaCaT cells. The derivatives exerted better growth inhibitory profiles towards selected tumor cells than the reference cisplatin. Compounds incorporating 3,4-dichloro- (2) and 4-CF₃-phenyl (8) substituents displayed the highest activity (IC₅₀ from 1.5 to 8.9 µM). The mechanisms of cytotoxic action of the most effective thioureas 1-3, 8, and 9 were studied, including the trypan blue exclusion test of cell viability, interleukin-6, and apoptosis assessments. Compounds reduced all cancerous cell numbers (especially SW480 and SW620) by 20-93%. Derivatives 2 and 8 diminished the viability of SW620 cells by 45-58%. Thioureas 1, 2, and 8 exerted strong pro-apoptotic activity. Compound 2 induced late apoptosis in both colon cancer cell lines (95-99%) and in K-562 cells (73%). All derivatives acted as inhibitors of IL-6 levels in both SW480 and SW620 cells, decreasing its secretion by 23-63%.

The Cytotoxic Effect of Copper (II) Complexes with Halogenated 1,3-Disubstituted Arylthioureas on Cancer and Bacterial Cells

A series of eight copper (II) complexes with 3-(4-chloro-3-nitrophenyl)thiourea were designed and synthesized. The cytotoxic activity of all compounds was assessed in three human cancer cell lines (SW480, SW620, PC3) and human normal keratinocytes (HaCaT). The complexes 1, 3, 5, 7 and 8 were cytotoxic to the studied tumor cells in the low micromolar range, without affecting the normal cells. The complexes 1, 3, 7 and 8 induced lactate dehydrogenase (LDH) release in all cancer cell lines, but not in the HaCaT cells. They provoked early apoptosis in pathological cells, especially in SW480 and PC3 cells. The ability of compounds 1, 3, 7 and 8 to diminish interleukin-6 (IL-6) concentration in a cell was established. For the first time, the influence of the most promising Cu (II) complexes on intensities of detoxifying and reactive oxygen species (ROS) scavenging the enzymes of tumor cells was studied. The cytotoxic effect of all copper (II) conjugates against standard and hospital bacterial strains was also proved.

Discovery of metal-based complexes as promising antimicrobial agents

The antimicrobial resistance (AMR) is an intractable problem for the world. Metal ions are essential for the cell process and biological function in microorganisms. Many metal-based complexes with the potential for releasing ions are more likely to be absorbed for their higher lipid solubility. Hence, this review highlights the clinical potential of organometallic compounds for the treatment of infections caused by bacteria or fungi in recent five years. The common scaffolds, including antimicrobial peptides, N-heterocyclic carbenes, Schiff bases, photosensitive-grand-cycle skeleton structures, aliphatic amines-based ligands, and special metal-based complexes are summarized here. We also discuss their therapeutic targets and the risks that should be paid attention to in the future studies, aiming to provide information for researchers on metal-based complexes as antimicrobial agents and inspire the design and synthesis of new antimicrobial drugs.

Structure and anticancer activity of Cu(II) complexes with (bromophenyl)thiourea moiety attached to the polycyclic imide

A series of nine copper complexes were synthesized by reacting 1,3-disubstituted thioureas with copper(II) chloride. The new compounds were characterized by elemental analysis, infrared, ultraviolet-visible and X-ray absorption spectroscopies as well as molecular modelling. The molecular structure of complexes in the solid state consists of two thiourea ligands chelated to the Cu(II) ion through the S and deprotonated N atoms (CuN₂S₂). The coordination polyhedron of metal cation in powdered samples exhibits two different geometries. Pseudo-tetrahedral structure is observed for noncentrosymmetric complexes with cis-N₂S₂ arrangement around Cu(II). A distorted square planar geometry is characteristic for centrosymmetric compounds with trans arrangements of chelating atoms around the central ion. All complexes after dissolving in dimethyl sulfoxide adopt a centrosymmetric coordination, while after diluting this solution with water, the reorganization of atoms around the metal cation is observed, leading to the formation of a tetrahedral compounds. Initial ligands and Cu(II) complexes were evaluated for their cytotoxicity. Two complexes with 4- and 3-bromophenyl attached to the (1,7,8,9,10-pentamethyl-3,5-dioxo-4-azatricyclo[5.2.1.0^2,6]dec-8-en-4-yl)thiourea moiety (Cu1, Cu3) are cytotoxic against SW480 and PC3 cells (IC₅₀ 4-19 μm), and non-cytotoxic against HaCaT cells (IC₅₀ ≥ 84 μm), being more selective than doxorubicin and cisplatin used as references. The compounds induced apoptosis in cancer cells, however, Cu3 was estimated to be highly active inducer of late apoptosis in SW480 and PC3 cells at lower toxicity against normal cells. The likely mechanism of action of complexes is correlated with decreasing release of IL-6 in cancer cell lines.

Antimicrobial Activity of Protein Fraction from Naja ashei Venom Against Staphylococcus epidermidis

One of the key problems of modern infectious disease medicine is the growing number of drug-resistant and multi-drug-resistant bacterial strains. For this reason, many studies are devoted to the search for highly active antimicrobial substances that could be used in therapy against bacterial infections. As it turns out, snake venoms are a rich source of proteins that exert a strong antibacterial effect, and therefore they have become an interesting research material. We analyzed Naja ashei venom for such antibacterial properties, and we found that a specific composition of proteins can act to eliminate individual bacterial cells, as well as the entire biofilm of Staphylococcus epidermidis. In general, we used ion exchange chromatography (IEX) to obtain 10 protein fractions with different levels of complexity, which were then tested against certified and clinical strains of S. epidermidis. One of the fractions (F2) showed exceptional antimicrobial effects both alone and in combination with antibiotics. The protein composition of the obtained fractions was determined using mass spectrometry techniques, indicating a high proportion of phospholipases A₂, three-finger toxins, and L-amino acids oxidases in F2 fraction, which are most likely responsible for the unique properties of this fraction. Moreover, we were able to identify a new group of low abundant proteins containing the Ig-like domain that have not been previously described in snake venoms.

Synthesis, antimicrobial, antioxidant, cytotoxic, antiurease and molecular docking studies of N-(3-trifluoromethyl)benzoyl-N'-aryl thiourea derivatives

An irrefutable advancement has been noted for the infectious diseases caused due to ureolytic bacteria through the development of various drugs. Keeping in mind the extremely valuable synthetic utility and medicinal significance of thiourea derivatives, synthesis of new 3-trifluoromethyl benzoic acid thiourea derivatives (3a-j) were carried out. The biological potential of all compounds in terms of antimicrobial, antioxidant, cytotoxic and antiurease activities were studied. The compounds 3a, 3c and 3i with dichloro and methoxy groups substitution on the aryl group showed significant activity against all strain of bacteria while moderate to no activity was observed in remaining compounds. Whereas the antifungal evaluation showed that all compounds were active againts C. Albican and no activity was observed against C. Prapsilosis. The cytotoxic findings revealed the non-toxic nature of these compounds as IC₅₀ values of majority of the compounds are above 100 μm except for compounds 3f and 3g. In addition, these compounds exhibited better antioxidant potential as 100 μm concentration inhibited >50% reactive oxygen species (ROS) production except compounds 3e, 3f and 3j. The compound 3a proved to be the most potent urease inhibitor showing the highest enzyme % inhibition (93.1%) with IC₅₀ value of 8.17 ± 0.24 µM and found more active as compare to standard followed by compound 3e (92.6%), 3h (91.6%), 3d (90.8%), 3b (90.6%) and 3f (90.0%) with their respective IC₅₀ values. All the synthesized compounds were docked into the binding cavity of Urease (PDB ID: 4ubp). The most active compound 3a was also ranked as top on the docking score as it was found to show valuable interactions with the target protein along with good docking scores. Hence our results revealed that the synthesized compounds have potential to be used as potent urease inhibitors after further detailed mechanistic studies.

Disubstituted 4-Chloro-3-nitrophenylthiourea Derivatives: Antimicrobial and Cytotoxic Studies

4-Chloro-3-nitrophenylthioureas 1–30 were synthesized and tested for their antimicrobial and cytotoxic activities. Compounds exhibited high to moderate antistaphylococcal activity against both standard and clinical strains (MIC values 2–64 μg/mL). Among them derivatives with electron-donating alkyl substituents at the phenyl ring were the most promising. Moreover, compounds 1–6 and 8–19 were cytotoxic against MT-4 cells and various other cell lines derived from human hematological tumors (CC₅₀ ≤ 10 μM). The influence of derivatives 11, 13 and 25 on viability, mortality and the growth rate of immortalized human keratinocytes (HaCaT) was observed.

Design and synthesis of novel 1H-tetrazol-5-amine based potent antimicrobial agents: DNA topoisomerase IV and gyrase affinity evaluation supported by molecular docking studies

A total of 14 of 1,5-disubstituted tetrazole derivatives were prepared by reacting appropriate thiourea and sodium azide in the presence of mercury (II) chloride and triethylamine. All compounds were evaluated in vitro for their antimicrobial activity. Derivatives 10 and 11 showed the highest inhibition against Gram-positive and Gram-negative strains (standard and hospital strains). The observed minimal inhibitory concentrations values were in the range of 1-208 μM (0.25-64 μg/ml). Inhibitory activity of 1,5-tetrazole derivatives 10 and 11 against gyrase and topoisomerase IV isolated from S. aureus was studied. Evaluation was supported by molecular docking studies for all synthesized derivatives and reference ciprofloxacin. Moreover, selected tetrazoles (2, 3, 5, 6, 8, 9, 10 and 11) were evaluated for their cytotoxicity. All tested compounds are non-cytotoxic against HaCaT and A549 cells (CC₅₀ ≤ 60 μM).