Influence of terminal substitution on structural, DNA, protein binding, anticancer and antibacterial activities of palladium(II) complexes containing 3-methoxy salicylaldehyde-4(N) substituted thiosemicarbazones

Effect of ruthenium(II) complexes on MDA-MB-231 cells and lifespan/tumor growth in gld-1mutant, Daf-16 TF and stress productive genes: A perspective study

Pincer type coumarin based N-substituted semicarbazone ligands HL1-4 and their corresponding ruthenium(II) complexes (1-4) were synthesized, analyzed and confirmed by various spectro analytical techniques. The molecular structure of the ligand HL3 and complex 3 was confirmed by single crystal X-ray diffraction analysis. The stoichiometry of complexes 1, 2 and 4 was confirmed by high resolution mass spectroscopy (HRMS). The binding affinity of the compounds with CT-DNA (Calf Thymus DNA) and BSA (Bovine Serum Albumin) was established by absorption and emission titration methods. The results of In vitro cytotoxicity showed the significant cytotoxic potential of the complexes against MDA-MB-231 cells (TNBC- Triple-negative breast cancer). Among the complexes, 1 and 4 have shown appreciable results. Further, antimigratory activity against the MDA-MB-231 cells was studied for the complexes 1 and 4. The percentage cell cycle arrest, apoptosis and necrosis were explored by flow cytometry. The in vivo anti-tumor activity of the complexes 1 and 4 using C. elegans as model organism was established by using the tumoral C. elegans strain JK1466 (gld-1(q485)), which bears a mutation in the gld-1 tumor suppressor gene. We have determined the effect of our complexes on tumor gonad reduction and found to be non toxic to the JK1466 worms and they have prolonged their mean lifespan with potential antioxidant ability by overcoming stress responses. Overall, our study reported herein demonstrated that the complexes 1 and 4 could be established as potential metallo-drugs substantiating further exploration.

Novel palladium(II) and Zinc(II) Schiff base complexes: Synthesis, biophysical studies, and anticancer activity investigation

BACKGROUND

Schiff base metal complexes are considered promising chemotherapeutic agents due to their potential application in cancer therapy.

METHODS

The current work sought to synthesize a brand-new Schiff base ligand obtained from 2-hydroxybenzohydrazide and (E)- 1-(2-(p-tolyl)hydrazono)propan-2-one with metal ions which included Pd(II) and Zn(II) ions. Elemental analyses, FT-IR, mass spectra, 1H NMR, UV-Vis spectrometer, and computational analysis characterized the compound's structure. In vitro, the breast cancer cell line (MCF-7) was tested for its sensitivity to Schiff base (HL) and its Pd(II) and Zn(II) complexes. The half-maximal inhibitory concentration IC₅₀ of the compounds was determined and used to perform the comet assay, which was carried out to reveal the photo-induced DNA damaging ability of the compounds of individual cells. Moreover, the compounds' effects on antioxidant defense systems of enzymes in cells: superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities and oxidant Malondialdehyde (MDA) were examined in MCF-7 cells.

RESULTS

The Pd(II) complex displayed approximately the same IC₅₀ as Cisplatin, while Zn(II) complex had better activity than Cisplatin with very low IC₅₀, 1.40 μg/ml. Significant alterations in SOD, CAT, GPx, and MDA production were discovered, inducing oxidative stress, enlarging ROS production, and reducing the antioxidant amount. This change was approximately similar in most compounds. Consequently, it promoted apoptosis, particularly the Zn(II) complex, which demonstrated an improved impact because of its ability to influence the antioxidant defense systems of enzymes, mostly SOD and GPx, besides increasing MDA levels.

CONCLUSION

It can be concluded that Zn(II) complex is the most effective anticancer drug since it induced a very similar genotoxic effect as Cisplatin and has a very low IC₅₀ value.

Metals to combat antimicrobial resistance

Bacteria, similar to most organisms, have a love-hate relationship with metals: a specific metal may be essential for survival yet toxic in certain forms and concentrations. Metal ions have a long history of antimicrobial activity and have received increasing attention in recent years owing to the rise of antimicrobial resistance. The search for antibacterial agents now encompasses metal ions, nanoparticles and metal complexes with antimicrobial activity ('metalloantibiotics'). Although yet to be advanced to the clinic, metalloantibiotics are a vast and underexplored group of compounds that could lead to a much-needed new class of antibiotics. This Review summarizes recent developments in this growing field, focusing on advances in the development of metalloantibiotics, in particular, those for which the mechanism of action has been investigated. We also provide an overview of alternative uses of metal complexes to combat bacterial infections, including antimicrobial photodynamic therapy and radionuclide diagnosis of bacterial infections.

New Mononuclear and Binuclear Cu(II), Co(II), Ni(II), and Zn(II) Thiosemicarbazone Complexes with Potential Biological Activity: Antimicrobial and Molecular Docking Study

Herein, we report the synthesis of eight new mononuclear and binuclear Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ methoxy thiosemicarbazone (MTSC) complexes aiming at obtaining thiosemicarbazone complex with potent biological activity. The structure of the MTSC ligand and its metal complexes was fully characterized by elemental analysis, spectroscopic techniques (NMR, FTIR, UV-Vis), molar conductivity, thermogravimetric analysis (TG), and thermal differential analysis (DrTGA). The spectral and analytical data revealed that the obtained thiosemicarbazone-metal complexes have octahedral geometry around the metal center, except for the Zn²⁺-thiosemicarbazone complexes, which showed a tetrahedral geometry. The antibacterial and antifungal activities of the MTSC ligand and its (Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) metal complexes were also investigated. Interestingly, the antibacterial activity of MTSC- metal complexes against examined bacteria was higher than that of the MTSC alone, which indicates that metal complexation improved the antibacterial activity of the parent ligand. Among different metal complexes, the MTSC- mono- and binuclear Cu²⁺ complexes showed significant antibacterial activity against Bacillus subtilis and Proteus vulgaris, better than that of the standard gentamycin drug. The in silico molecular docking study has revealed that the MTSC ligand could be a potential inhibitor for the oxidoreductase protein.

Condensed-phase relative Gibbs free energy and E/Z descriptors for 2-acetylthiophene and 2-acetylthiophene-N1-phenyl thiosemicarbazones

Thiosemicarbazones (TSCs) encompasses a class of compounds relevant in the pharmacological context. Their specific applicability varies in function of the appropriated chemical modification and their binding to different transition metals. In the present work, we apply current standards functionals, B3LYP and B97D, with triple zeta basis set quality, 6-311++G(d,p), to investigate the relative stability of the various possible spatial arrangements for 2-acetylthiophene and 2-acetylthiophene-N1-phenyl thiosemicarbazones, denoted ATTSC and ATTSC-Ph, respectively. The relative stability of neutral and deprotonated species at ethanol described by an implicit solvent model was investigated. For ATTSC, the relative Gibbs energy changed significantly upon deprotonation, and for ATTSC-Ph, a novel global minimum was identified. Based on the present study, deprotonation determines population in condensed-media. Such information, valid for ATTSC and ATTSC-Ph, can be crucial in studying other thiosemicarbazones.

Di-n-but-yl[N'-(3-meth-oxy-2-oxidobenzyl-idene)-N-phenyl-carbamohydrazono-thio-ato]tin(IV): crystal structure, Hirshfeld surface analysis and computational study

The title diorganotin Schiff base derivative, [Sn(C4H9)2(C15H13N3O2S)], features a penta-coordinated tin centre defined by the N,O,S-donor atoms of the di-anionic Schiff base ligand and two methyl-ene-C atoms of the n-butyl substituents. The resultant C2NOS donor set defines a geometry inter-mediate between trigonal-bipyramidal and square-pyramidal. In the crystal, amine-N-H⋯O(meth-oxy) hydrogen bonding is found in a helical, supra-molecular chain propagating along the b-axis direction. The chains are assembled into a layer parallel to (01) with methyl-ene-C-H⋯π(phen-yl) inter-actions prominent; layers stack without directional inter-actions between them. The analysis of the calculated Hirshfeld surface showed the presence of weak methyl-ene-C-H⋯π(phen-yl) inter-actions and short H⋯H contacts in the inter-layer region. Consistent with the nature of the identified contacts, the stabilization of the crystal is dominated by the dispersion energy term.

Palladium-mediated C–O bond activation of benzopyrone in 4-oxo-4H-chromone-3-carbaldehyde-4(N)-substituted thiosemicarbazone: synthesis, structure, nucleic acid/albumin interaction, DNA cleavage, antioxidant and cytotoxic studies

Palladium ion-mediated C–O activation at the C2 carbon of the benzopyrone moiety of 3-formylchromone-4(N)-substituted thiosemicarbazone (HL1–4) has been observed in square-planar palladium(ii) complexes.

A review on 1,1-bis(diphenylphosphino)methane bridged homo- and heterobimetallic complexes for anticancer applications: Synthesis, structure, and cytotoxicity

Herein, we review developments in synthesis, structure, and biological (anti-cancer) activities of 1,1-bis(diphenylphosphino)methane (dppm) bridged homo- and heterobimetallic systems of the type L_mM(μ₂-dppm)M'L_n (M and M' are transition metals which may be different or the same and L_n,m are co-ligands) since the first such reported bimetallic system in 1987 until the present time (2020). As the simplest diphosphine, dppm enables facile formation of bimetallic complexes, where, given the short spacer between the PPh₂ groups, close spatial proximity of the metal centres is ensured. We concentrate on complexes bearing no M-M interaction and contrast biological activities of these complexes with mononuclear counterparts and positive control agents such as cisplatin, in an attempt to elucidate patterns in the biological activities of these complexes.

Synthesis, structural, cytotoxic and pharmacokinetic evaluation of some thiosemicarbazone derivatives

Iron(III) and nickel(II) complexes bearing a thiosemicarbazone framework were synthesized by a one-pot synthesis method. The structures were characterized by elemental analysis, IR, ¹ H NMR, APCI Mass, conductivity, magnetic moment measurements. Molecular and crystal structures of the iron(III) complex were obtained from single-crystal X-ray diffraction. The findings showed that the metal atom adopts a slightly distorted square-pyramidal coordination, with the four donor atoms of the thiosemicarbazone ligand defining the basal plane and a chloride atom occupying the apical position. In the crystal lattice, the structure is stabilized by intermolecular O─H···O and C─H···O interactions. The cytotoxic activity was studied by MTT assay, the expression levels of cytochrome P450 (CYP) enzymes by Western blot, and the lipophilicity (LogP) by using the shake-flask method, another pharmacokinetic parameter. The findings showed that the IC₅₀ values decreased with the decrease of the LogP values of the substances. Cytochrome P450 expression levels were found specific for each compound and each cell line. As a result, the pharmacokinetic properties of the newly synthesized thiosemicarbazone compounds are crucial for oral administration and provide us with clues for prospective in vivo studies.

Metal Complexes, an Untapped Source of Antibiotic Potential?

With the widespread rise of antimicrobial resistance, most traditional sources for new drug compounds have been explored intensively for new classes of antibiotics. Meanwhile, metal complexes have long had only a niche presence in the medicinal chemistry landscape, despite some compounds, such as the anticancer drug cisplatin, having had a profound impact and still being used extensively in cancer treatments today. Indeed, metal complexes have been largely ignored for antibiotic development. This is surprising as metal compounds have access to unique modes of action and exist in a wider range of three-dimensional geometries than purely organic compounds. These properties make them interesting starting points for the development of new drugs. In this perspective article, , the encouraging work that has been done on antimicrobial metal complexes, mainly over the last decade, is highlighted. Promising metal complexes, their activity profiles, and possible modes of action are discussed and issues that remain to be addressed are emphasized.

Synthesis, Crystal Structure, and Biological Activity of a Multidentate Calix[4]arene Ligand Doubly Functionalized by 2-Hydroxybenzeledene-Thiosemicarbazone

The design and synthesis of a novel tert-butyl-calix[4]arene functionalized at 1, 3 positions of the lower rim with two terminal 2-hydroxybenzeledene-thiosemicarbazone moieties is reported. The new ligand with multi-dentate chelating properties was fully characterized by several techniques: ESI-Mass spectroscopy, FT-IR, 1H-NMR, and single crystal X-ray diffraction. The solid state structure confirms that the calix[4]arene macrocycle has the expected open cone conformation, with two opposite phenyl rings inclined outwards with large angles. The conformation of the two alkoxythiosemicarbazone arms produces a molecule with a C2 point group symmetry. An interesting chiral helicity is observed, with the two thiosemicarbazone groups oriented in opposite directions like a two-blade propeller. A water molecule is encapsulated in the center of the two-blade propeller through multiple H-bond coordinations. The antibacterial, antifungal, anticancer, and cytotoxic activities of the calix[4]arene-thiosemicarbazone ligand and its metal derivatives (Co2+, Ni2+, Cu2+, and Zn2+) were investigated. A considerable antibacterial activity (in particular against E. coli, MIC, and MBC = 31.25 μg/mL) was observed for the ligand and its metal derivatives. Significant antifungal activities against yeast (C. albicans) were also observed for the ligand (MIC = 31.25 μg/mL and MBC = 125 μg/mL) and for its Co²⁺ derivative (MIC = 62.5 μg/mL). All compounds show cytotoxicity against the tested cancerous cells. For the Saos-2 cell line, the promising anticancer activity of ligand L (IC₅₀ < 25 μg/mL) is higher than its metal derivatives. The microscopic analysis of DAPI-stained cells shows that the treated cells change in morphology, with deformation and fragmentation of the nuclei. The hemo-compatibility study demonstrated that this class of compounds are suitable candidates for further in vivo investigations.

para metallation of 3-acetyl-chromen-2-one Schiff bases in tetranuclear palladacycles: focus on their biomolecular interaction and in vitro cytotoxicity

Three tetranuclear (1-3) complexes and a mononuclear (4) palladium(ii) complex were synthesized from 3-acetyl-chromen-2-one Schiff base ligands [H₂-3MAC-Rtsc] (where R = H [H₂-3MAC-tsc]; CH₃[H₂-3MAC-mtsc]; C₂H₅[H₂-3MAC-etsc] or C₆H₅[H₂-3MAC-ptsc]) and potassium tetrachloropalladate. Their formation was confirmed by spectroscopic techniques and X-ray crystallographic analysis. Their ability to bind with DNA and albumin was analysed by using absorption and emission titrations. The MTT assay was carried out to analyze the anticancer potential of the ligands and synthesized complexes against HepG2 (human liver cancer) and HT-29 (human colon cancer) cells. In addition, the compounds were less toxic when tested against the human normal keratinocyte cells (HaCaT). Ligands and complexes displayed better cytotoxicity with lower IC₅₀ values than the standard drug cisplatin. Further AO-EB and DAPI staining assays were carried out to detect the mode of cell death induced by the complexes i.e. apoptosis or necrosis. The complex 3 showed better cytotoxicity and was further subjected to flow cytometric analysis. The results suggested that the complex 3 induced apoptotic cell death.

Organoruthenium(II) complexes attenuate stress in Caenorhabditis elegans through regulating antioxidant machinery

The 1:1 stoichiometric reactions of 3-methoxy salicylaldehyde-4(N)-substituted thiosemicarbazones (H₂L^1-4) with [RuCpCl(PPh₃)₂] was carried out in methanol. The obtained complexes (1-4) were characterized by analytical, IR, absorption and ¹H NMR spectroscopic studies. The structures of ligand [H₂-3MSal-etsc] (H₂L³) and complex [RuCp(Msal-etsc) (PPh₃)] (3), were characterized by single crystal X-ray diffraction studies. The interaction of the ruthenium(II) complexes (1-4) with calfthymus DNA (CT-DNA) has been explored by absorption and emission titration methods. Based on the observations, an intercalative binding mode of DNA has been proposed. The protein binding abilities of the new complexes were monitored by quenching the tryptophan and tyrosine residues of BSA, as model protein. From the studies, it was found that the new ruthenium metallacycles exhibited better affinity than their precursors. The free radical scavenging assay suggests that all complexes effectively scavenged the DPPH radicals as compared to that of standard control ascorbic acid and scavenging activities of complexes are in the order of 4 > 2 > 3 > 1. In addition, ruthenium(II) complexes (2-4) also exhibited an excellent in vivo antioxidant activity as it was able to increase the survival of worms exposed to lethal oxidative and thermal stresses possibly through reducing the intracellular ROS levels. It was interesting to note that complexes 2-4 failed to increase the lifespan of mev-1 mutant worms having shortened lifespan due to the over production of free radicals. This data confirmed that complexes 2-4 conferred stress resistance in C. elegans, but they also require an endogenous detoxification mechanism for doing so. The genetic and reporter gene expression analysis revealed that complexes 2-4 maintained the intracellular redox status and offered stress protection through transactivation of antioxidant defence machinery genes gst-4 and sod-3 which are directly regulated by SKN-1 and DAF-16 transcription factors, respectively. Altogether, our results suggested that complexes 2-4 might play a crucial role in stress modulation and they perhaps exert almost similar effects in higher models, which is an important issue to be validated in future.

Synthesis, reactivity, and antimicrobial properties of boron-containing 4-ethyl-3-thiosemicarbazide derivatives

The addition of 4-ethyl-3-thiosemicarbazide to benzaldehyde and boronic acid containing derivatives afforded the corresponding thiosemicarbazones (1–3) or benzodiazaborines (4–6) depending on the position of the boronic acid within the ring. All compounds have been characterized fully including an X-ray diffraction study of the methoxy-containing benzodiazaborine 6. Attempts to coordinate thiosemicarbazones 2 and 3 to palladium(II) acetate were unsuccessful; however, addition of the non-boron-containing derivative 1 to palladium afforded complex 7 whose molecular structure was determined by an X-ray diffraction study. The initial bioactivities of compounds 1–7 were examined against two fungi, Aspergillus niger and Saccharomyces cerevisiae, and two bacteria, Bacillus cereus and Pseudomonas aeruginosa.

Synthesis, structures and mechanistic pathways of anticancer activity of palladium(ii) complexes with indole-3-carbaldehyde thiosemicarbazones

Palladium(ii) complexes featuring bidentate heterocyclic thiosemicarbazones have been synthesized, characterized and evaluated for their biomolecular interactions. The complexes induced in vitro anticancer activity through apoptosis.