Synthesis, characterization, DNA interaction, antioxidant and anticancer activity of new ruthenium(II) complexes of thiosemicarbazone/semicarbazone bearing 9,10-phenanthrenequinone

Structural and Functional Diversity in Rigid Thiosemicarbazones with Extended Aromatic Frameworks: Microwave-Assisted Synthesis and Structural Investigations

The long-standing interest in thiosemicarbazones (TSCs) has been largely driven by their potential toward theranostic applications including cellular imaging assays and multimodality imaging. We focus herein on the results of our new investigations into: (a) the structural chemistry of a family of rigid mono(thiosemicarbazone) ligands characterized by extended and aromatic backbones and (b) the formation of their corresponding thiosemicarbazonato Zn(II) and Cu(II) metal complexes. The synthesis of new ligands and their Zn(II) complexes was performed using a rapid, efficient and straightforward microwave-assisted method which superseded their preparation by conventional heating. We describe hereby new microwave irradiation protocols that are suitable for both imine bond formation reactions in the thiosemicabazone ligand synthesis and for Zn(II) metalation reactions. The new thiosemicarbazone ligands, denoted HL, mono(4-R-3-thiosemicarbazone)quinone, and their corresponding Zn(II) complexes, denoted ZnL₂, mono(4-R-3-thiosemicarbazone)quinone, where R = H, Me, Ethyl, Allyl, and Phenyl, quinone = acenapthnenequinone (AN), aceanthrenequinone (AA), phenanthrenequinone (PH), and pyrene-4,5-dione (PY) were isolated and fully characterized spectroscopically and by mass spectrometry. A plethora of single crystal X-ray diffraction structures were obtained and analyzed and the geometries were also validated by DFT calculations. The Zn(II) complexes presented either distorted octahedral geometry or tetrahedral arrangements of the O/N/S donors around the metal center. The modification of the thiosemicarbazide moiety at the exocyclic N atoms with a range of organic linkers was also explored, opening the way to bioconjugation protocols for these compounds. The radiolabeling of these thiosemicarbazones with ⁶⁴Cu was achieved under mild conditions for the first time: this cyclotron-available radioisotope of copper (t_1/2 = 12.7 h; β+ 17.8%; β- 38.4%) is well-known for its proficiency in positron emission tomography (PET) imaging and for its theranostic potential, on the basis of the preclinical and clinical cancer research of established bis(thiosemicarbazones), such as the hypoxia tracer ⁶⁴Cu-labeled copper(diacetyl-bis(N4-methylthiosemicarbazone)], [⁶⁴Cu]Cu(ATSM). Our labeling reactions proceeded in high radiochemical incorporation (>80% for the most sterically unencumbered ligands) showing promise of these species as building blocks for theranostics and synthetic scaffolds for multimodality imaging probes. The corresponding "cold" Cu(II) metalations were also performed under the mild conditions mimicking the radiolabeling protocols. Interestingly, room temperature or mild heating led to Cu(II) incorporation in the 1:1, as well as 1:2 metal: ligand ratios in the new complexes, as evident from extensive mass spectrometry investigations backed by EPR measurements, and the formation of Cu(L)₂-type species prevails, especially for the AN-Ph thiosemicarbazone ligand (L^-). The cytotoxicity levels of a selection of ligands and Zn(II) complexes in this class were further tested in commonly used human cancer cell lines (HeLa, human cervical cancer cells, and PC-3, human prostate cancer cells). Tests showed that their IC₅₀ levels are comparable to that of the clinical drug cis-platin, evaluated under similar conditions. The cellular internalizations of the selected ZnL₂-type compounds Zn(AN-Allyl)₂, Zn(AA-Allyl)₂, Zn(PH-Allyl)₂, and Zn(PY-Allyl)₂ were evaluated in living PC-3 cells using laser confocal fluorescent spectroscopy and these experiments showed exclusively cytoplasmic distributions.

Switching of the Polarity-Sensitive Aggregation Pattern of a Thiosemicarbazone-Based Anticancer Luminophore and Its Involvement in Cellular Apoptosis of the Human Lung Cancer Cell Line

Elucidation of the photophysical and biochemical properties of small molecules can facilitate their applications as prospective therapeutic imaging (theragnostic) agents. Herein, we demonstrate the luminescence behavior of a strategically designed potential therapeutic thiosemicarbazone derivative, (E)-1-(4-(diethylamino)-2-hydroxybenzylidene)-4,4-dimethylthiosemicarbazide (DAHTS), accompanied by the illustration of its solvation and solvation dynamics using spectroscopic techniques and exploring its promising antitumor activities by adopting the necessary biochemical assays. Solvent-dependent photophysical properties, namely UV-vis absorption, fluorescence emission, and excitation profiles, concentration-dependent studies, and time-resolved fluorescence decays, serve as footprints to explain the existence of DAHTS monomers, its excited-state intramolecular proton transfer (ESIPT) product, and dimeric and aggregated forms. The emission intensity progressively intensifies with increasing polarity and proticity of the solvents up to MeOH, but in water, a sudden dip is seen. Solvent polarity and H-bonding modulate the fluorescence behavior of the primary emission peak and significantly influence the formation of the dimer and DAHTS aggregates. The designed luminophore (DAHTS) exhibits significant antiproliferative activity against the human lung cancer (A549) cell lines with inhibitory concentrations (IC₅₀) of 16.88 and 11.92 μM for 24 and 48 h, respectively. DAHTS effectively reduces the cell viability and induces cytotoxicity with extensive morphological changes in A549 cells in the form of spikes when compared to the normal HEK cell lines. More importantly, it increases the p53 expression at the mRNA level that consolidates its potential therapeutic activity. The effect of DAHTS on apoptotic pathways against the A549 cell line has been investigated to determine its probable mechanism of cell death. Thus, the all-inclusive understanding of the photophysical properties and the necessary biochemical assays put forward important steps toward tailoring the thiosemicarbazone core structure for favorable cancer theragnostic applications in academic and pharmaceutical research.

NSAID-Based Coordination Compounds for Biomedical Applications: Recent Advances and Developments

After the serendipitous discovery of cisplatin, a platinum-based drug with chemotherapeutic effects, an incredible amount of research in the area of coordination chemistry has been produced. Other transition metal compounds were studied, and several new relevant metallodrugs have been synthetized in the past few years. This review is focused on coordination compounds with first-row transition metals, namely, copper, cobalt, nickel or manganese, or with zinc, which have potential or effective pharmacological properties. It is known that metal complexes, once bound to organic drugs, can enhance the drugs’ biological activities, such as anticancer, antimicrobial or anti-inflammatory ones. NSAIDs are a class of compounds with anti-inflammatory properties used to treat pain or fever. NSAIDs’ properties can be strongly improved when included in complexes using their compositional N and O donor atoms, which facilitate their coordination to metal ions. This review focuses on the research on this topic and on the promising or effective results that complexes of first-row transition metals and NSAIDs can exhibit.

Novel indole-thiazole and indole-thiazolidinone derivatives as DNA groove binders

In this study, we report the synthesis of eight novel indole-thiazole and indole-thiazolidinone derivatives, as well as their ability to interact with DNA, analysed through the UV-vis absorption, fluorescence, circular dichroism (CD), viscosity techniques and molecular docking. The ctDNA interaction analysis demonstrated different spectroscopic effects and the affinity constants (Kb) calculated by the UV-vis absorption method were between 2.08 × 10⁵ and 6.99 × 10⁶ M^-1, whereas in the fluorescence suppression constants (Ksv) ranged between 0.38 and 0.77 × 10⁴ M^-1 and 0.60-7.59 × 10⁴ M^-1 using Ethidium Bromide (EB) and 4',6-Diamidino-2-phenylindole (DAPI) as fluorescent probes, respectively. Most derivatives did not alter significantly the secondary structure of the ctDNA according to the CD results. None of the compounds was able to change the relative viscosity of the ctDNA. These results prove that compounds interact with ctDNA via groove binding, which was confirmed by A-T rich oligonucleotide sequence assay with compound JF-252, suggesting the importance of both the phenyl ring coupled to C-4 thiazole ring and the bromo-unsubstituted indole nucleus.

The remarkable selectivity of the 2-arylquinoline-based acyl hydrazones toward copper salts: exploration of their catalytic applications in the copper catalysed N-arylation of indole derivatives and C1-alkynylation of tetrahydroisoquinolines via the A3 reaction

Different selective 2-arylquinoline-based acyl hydrazones toward copper(i) salts were synthesised, characterized and studied their applicability as metal ligands in diverse chemical transformations.

Study on the Interaction of 4'-Hydroxychalcones and their Mannich Derivatives with Calf Thymus DNA by TLC and Spectroscopic Methods, a DNA Cleavage Study

Background:

Phenolic Mannich bases derived from hydroxychalcones show remarkable cytotoxic potencies towards cancer cell lines. However, the exact mechanism of action is still partially uncleared.

Objective:

Interaction of two hydroxychalcones and their Mannich derivatives with calf thymus DNA (ctDNA) has been investigated.

Methods:

Thin-layer chromatography and UV-Vis spectroscopic method were used for studying the interaction. The binding constant has been determined by UV-Vis spectrophotometric titration. The DNA cleavage activity of the compounds was studied by agarose gel electrophoresis.

Results:

Interaction of the compounds with ctDNA exhibited relatively high intrinsic binding constant (4-5x104 M-1). The results indicate existence of weak, non-covalent interactions between the investigated derivatives with ctDNA. Some compounds showed a slight DNA cleavage activity with pBR322.

Conclusion:

The obtained results provide additional knowledge on the previously documented cytotoxicity against tumor cell lines of the hydroxychalcones and their Mannich-derivatives.

Cytotoxicity of Air Pollutant 9,10-Phenanthrenequinone: Role of Reactive Oxygen Species and Redox Signaling

Atmospheric pollution has been a principal topic recently in the scientific and political community due to its role and impact on human and ecological health. 9,10-phenanthrenequinone (9,10-PQ) is a quinone molecule found in air pollution abundantly in the diesel exhaust particles (DEP). This compound has studied extensively and has been shown to develop cytotoxic effects both in vitro and in vivo. 9, 10-PQ has been proposed to play a critical role in the development of cytotoxicity via generation of reactive oxygen species (ROS) through redox cycling. This compound also reduces expression of glutathione (GSH), which is critical in Phase II detoxification reactions. Understanding the underlying cellular mechanisms involved in cytotoxicity can allow for the development of therapeutics designed to target specific molecules significantly involved in the 9,10-PQ-induced ROS toxicity. This review highlights the developments in the understanding of the cytotoxic effects of 9, 10-PQ with special emphasis on the possible mechanisms involved.

Nickel(II) bis(isatin thiosemicarbazone) complexes induced apoptosis through mitochondrial signaling pathway and G0/G1 cell cycle arrest in IM-9 cells

Three novel complexes (1, 3 and 4) ligating N-substituted isatin thiosemicarbazone derivatives have been synthesized and their structural and biological characteristics have been compared with those of the known analogs (2, 5-7 and 8). In addition, the structure of the representative ligands (L1, L3 and L4) and complex (4) was confirmed by single crystal X-ray diffraction method. All the complexes (1-8) were assessed for their cytotoxic property against a panel of four human cancer cells such as HepG-2 (liver), MOLM-14 (acute monocytic leukemia), U937 (histiocytic lymphoma). and IM-9 (myeloma). Complex 4 exhibited prominent cytotoxic property against MOLM-14, U937 and IM-9 cell lines. Moreover, the results were compared with the well-known anticancer drugs like doxorubicin, cisplatin and daunorubicin. Besides, complex 4 enhanced the apoptotic cell death in IM-9 cell line and induced cell cycle arrest at G1 phase. Western blot analysis revealed the down-regulation of Bcl-2 (b-cell lymphoma-2), up-regulation of Bax (bcl-2 associated X protein), release of cytochrome c and activation of caspases-3 in IM-9 cells by complex 4. Importantly, complex 4 was not toxic to the normal Vero cell line (IC₅₀ > 300 μM). In addition, complex 4 showed the concentration dependent cleavage of supercoiled (SC) DNA to its nicked circular (NC) form.

Structurally different mono-, bi- and trinuclear Pd(ii) complexes and their DNA/protein interaction, DNA cleavage, and anti-oxidant, anti-microbial and cytotoxic studies

A series of new structurally different Pd(ii) complexes was obtained by the reactions between K₂[PdCl₄], 3-methoxysalicylaldehyde-4(N)-substituted thiosemicarbazone [H₂L1–H₂L4] and bis(diphenylphosphino)ethane [dppe].

Mixed-ligand copper(ii) Schiff base complexes: the vital role of co-ligands in DNA/protein interactions and cytotoxicity

Four new mixed-ligand copper(ii) complexes display an antibacterial mechanism of cell death via cell-wall rupture and cytotoxicity via apoptotic cell death.

cis-Dioxomolybdenum(VI) complexes of a new ONN chelating thiosemicarbazidato ligand; synthesis, characterization, crystal, molecular structures and antioxidant activities

5-Chloro-4-methyl-2-hydroxybenzophenone S-propyl-4-phenyl-thiosemicarbazone (H2L) and its cis-dioxomolybdenum(VI) complexes, in the general formula [MoO2(L)R-OH)] (R: methyl, 1; ethyl, 2; n-propyl, 3; n-butyl, 4; n-pentyl, 5), were synthesized and characterized by micro analysis, electronic, infrared and (1)H and (13)C NMR spectra. The crystal structures of complexes, 1 and 3, have been solved by direct methods (SIR92) and refined to the residual indexes R1=0.098 and R1=0.052 respectively. Complexes 1 and 3 are crystallized in the triclinic space group P-1 with Z=2. The crystal study of complex 1 showed the first example of intermolecular hydrogen bond for this type of molybdenum-thiosemicarbazone complexes. The hydrogen bond is between the hydroxyl proton of attached alcohol and an oxo oxygen (in MoO2(2+) unit) of another complex molecule, and its bond distance (1.767(1)Å) is shorter than from the σ-coordination bonds in complex 1. Antioxidant activities of the compounds were determined by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. Ligand showed 23.61% DPPH radical scavenging activity at 250 mg/L concentration. Cupric Reducing Antioxidant Capacity (CUPRAC) was also evaluated and trolox-equivalent antioxidant capacity (TEAC) values were found for ligand, 1 and 3 as 0.51, 0.33 and 0.30 respectively.

Effect of radiation on cytotoxicity, apoptosis and cell cycle arrest of human osteosarcoma MG-63 induced by a ruthenium(II) complex

Radiation has large influence on the cytotoxicity, apoptosis and cell cycle arrest. The bioactivity of ruthenium(II) complex [Ru(dmb)2(DBHIP)](ClO4)2 (Ru1) (DBHIP=2-(3,5-dibromo-4-hydroxylphenyl)imidazo[4,5-f][1,10]phenanthroline) was investigated in the absence and presence of radiation. The cytotoxicity of Ru1 against MG-63 cells was evaluated by CCK-8 method. Ru1 shows high cytotoxicity upon radiation. Radiation can enhance the cytotoxicity of Ru1 on MG-63 cells. The apoptosis was studied by Hoechst 33258 staining method and flow cytometry. The reactive oxygen species, mitochondrial membrane potential, cell cycle arrest and western blot analysis were investigated in detail. The complex induces the apoptosis in MG-63 cells through ROS-mediated mitochondrial dysfunction pathway.

In vitro effects of binuclear (η (6)-p-cymene)ruthenium(II) complex containing bridging bis(nicotinate)-polyethylene glycol ester ligand on differentiation pathways of murine Th lymphocytes activated by T cell mitogen

T cell differentiation into distinct T helper (Th) subpopulations is crucial in governing acquired immune responses as well as some inflammatory and autoimmune disorders. This study investigated potential of the novel neutral binuclear ruthenium(II) complexes 1-8 with general formula [{RuCl2(η(6)-p-cym)}2μ-(N(∩)N)] (N(∩)N = bis(nicotinate)- and bis(iso-nicotinate)-polyethylene glycol esters; (3-py)COO(CH2CH2O) n CO(3-py) and (4-py)COO(CH2CH2O) n CO(4-py); n = 1-4), as well as [RuCl2(η(6)-p-cym)(nic)] (R1, nic = nicotinate) and [RuCl2(η(6)-p-cym)(inic)] (R2, inic = isonicotinate) as an immunomodulatory agents capable to direct Th cell differentiation. From all investigated complexes, [{RuCl2(η(6)-p-cym)}2μ-{(3-py)COO(CH2CH2O)4CO(3-py)}] (4) was selected for further study because it did not affect splenocyte viability (in concentration up to 50 μM), but significantly reduced secretion of representative Th1 cytokine, IFN-γ induced by T cell mitogen. Besides IFN-γ, 4 inhibited dose dependently expression and production of representative Th17 cytokine, IL-17, in these cells. Otherwise, the production of anti-inflammatory cytokines IL-4 and IL-10 was upregulated. Also, 4 significantly increased CD4(+)CD25(+)FoxP3(+) Treg cell frequency in the activated splenocytes. Moreover, ConA-induced expression of Th1 transcription factors, T-bet and STAT1, as well as of Th17-related protein STAT3 was attenuated upon exposure to 4, while the expression of Th2-related transcription factor GATA3 remained stable. In conclusion, ruthenium(II) complex 4 modulates immune system cell functions in vitro by inhibiting T cell differentiation towards pathogenic Th1/Th17 phenotype and inducing a regulatory phenotype characterized by IL-10 and IL-4 production, which may provide novel therapeutic opportunities for immune-inflammatory and/or autoimmune disorders.

Nickel(ii) and copper(ii) complexes constructed with N2S2 hybrid benzamidine–thiosemicarbazone ligand: synthesis, X-ray crystal structure, DFT, kinetico-catalytic and in vitro biological applications

We report nickel(ii) and copper(ii) complexes containing the benzamidine–thiosemicarbazone ligand together with DFT, enzyme kinetics and in vitro biological applications such as DNA/BSA affinities and anticancer properties.