Interaction with CT-DNA and in vitro cytotoxicity of two new copper(II)-based potential drugs derived from octanoic hydrazide ligands

Two copper(II) complexes [Cu(Hpmoh)(NO3)(NCS)] (1) and [Cu(peoh)(N3)]2 (2) were designed and synthesized by reaction of Cu(NO3)2·3H2O with hydrazone Schiff base ligands,abbreviated with Hpmoh and Hpeoh. Hpmoh and Hpeoh were prepared by condensation reaction of octanoic hydrazide with pyridine-2-carboxyaldehyde and 2-acetylpyridine, respectively. Complexes 1 and 2 were characterized using different analytical techniques such as FT-IR, UV-Vis, IR, EPR and single X-ray diffraction (XRD) analyses as well as computational methods (DFT). The XRD of 1 and 2 shows a mononuclear or a dinuclear structure with the copper(II) centre adopting a slightly distorted square pyramidal geometry. In water-containing solution and in DMSO, 1 and 2 undergo a partial transformation with formation of [Cu(Hpmoh)(NO3)(NCS)] (1) and [Cu(Hpmoh)(NO3)(H2O/DMSO)] (1a) in one system and [Cu(peoh)(N3)] (2a) in the other one, as supported by DFT calculations. Docking simulations confirmed that the intercalation is the preferred binding mode with DNA for 1, 1a and 2a, but suggested that the minor groove binding is also possible. A significant fluorescence quenching of the DNA-ethidium bromide conjugate was observed upon the addition of complexes 1 and 2 with a quenching constant around 104 M-1 s-1. Finally, both 1 and 2 were examined for anti-cancer activity using MDA-MB-231 (human breast adenocarcinoma) and A375 (malignant melanoma) cell lines through in vitro MTT assay which suggest comparable cancer cell killing efficacy, with the higher effectiveness of 2 due to the dissociation into two [Cu(peoh)(N3)] units.

Structure-Based Identification of Organoruthenium Compounds as Nanomolar Antagonists of Cannabinoid Receptors

Metal complexes exhibit a diverse range of coordination geometries, representing novel privileged scaffolds with convenient click types of preparation inaccessible for typical carbon-centered organic compounds. Herein, we explored the opportunity to identify biologically active organometallic complexes by reverse docking of a rigid, minimum-size octahedral organoruthenium scaffold against thousands of protein-binding pockets. Interestingly, cannabinoid receptor type 1 (CB1) was identified based on the docking scores and the degree of overlap between the docked organoruthenium scaffold and the hydrophobic scaffold of the cocrystallized ligand. Further structure-based optimization led to the discovery of organoruthenium complexes with nanomolar binding affinities and high selectivity toward CB2. Our work indicates that octahedral organoruthenium scaffolds may be advantageous for targeting the large and hydrophobic binding pockets and that the reverse docking approach may facilitate the discovery of novel privileged scaffolds, such as organometallic complexes, for exploring chemical space in lead discovery.

Recent advances in the development of metal complexes as antibacterial agents with metal-specific modes of action

The mounting burden of antimicrobial resistance (AMR) is one of the most concerning threats to public health worldwide. With low economic incentives and a dwindling supply of new drugs in clinical pipelines, more innovative approaches to novel drug design and development are desperately required. Metal-based compounds are rapidly emerging as an alternative to organic drugs, as they have the ability to kill pathogens via metal-specific modes of action. We herein review recent advances in metal-based antibacterial agents, including metal complexes, metal ions and catalytic metallodrugs. The review concludes with a perspective on the rational design of metal-based antibiotics, and how we can exploit their unique properties to tackle AMR.

Analytical insights into the detoxification process and characterization of a traditional metallopharmaceutical formulation

Metallopharmaceuticals possess unique medicinal properties and have been used since ancient times. In spite of the inclusion of several metals and minerals, there is an increased interest in metallo-drugs for clinical and research purposes because of their immense therapeutic efficiency and non-toxic claim, as they are processed in addition to specific poly herbals. Sivanar Amirtham is one of the traditional metallopharmaceuticals used in Siddha medicine to treat various respiratory diseases and other ailments, including antidote therapy for poisonous bites. The present research work attempted to formulate the metallodrug preparation as per the standard protocols, including the detoxification process of the raw materials, followed by the analytical characterization studies to evaluate the physicochemical properties responsible for the stability, quality, and efficacy. The study included the comparative analysis of the raw materials, processed samples, intermediate samples, finished products, and commercial samples to understand the science involved in detoxification and formulation processing. The appropriate product profile was developed based on analysis of the particle size and surface charge by Zeta sizer, morphology and distribution by SEM-EDAX, functional groups and chemical interactions by FTIR, thermal behavior and stability by TG-DSC, crystallinity by XRD, and elemental composition by XPS. The findings of the research could provide scientific proof of evidence to overcome the limitations of the product owing to the standard quality and safety concern of the metal-mineral constituents, such as mercury, sulphur, and arsenic in the polyherbomineral formulation.

Next Generation Gold Drugs and Probes: Chemistry and Biomedical Applications

The gold drugs, gold sodium thiomalate (Myocrisin), aurothioglucose (Solganal), and the orally administered auranofin (Ridaura), are utilized in modern medicine for the treatment of inflammatory arthritis including rheumatoid and juvenile arthritis; however, new gold agents have been slow to enter the clinic. Repurposing of auranofin in different disease indications such as cancer, parasitic, and microbial infections in the clinic has provided impetus for the development of new gold complexes for biomedical applications based on unique mechanistic insights differentiated from auranofin. Various chemical methods for the preparation of physiologically stable gold complexes and associated mechanisms have been explored in biomedicine such as therapeutics or chemical probes. In this Review, we discuss the chemistry of next generation gold drugs, which encompasses oxidation states, geometry, ligands, coordination, and organometallic compounds for infectious diseases, cancer, inflammation, and as tools for chemical biology via gold-protein interactions. We will focus on the development of gold agents in biomedicine within the past decade. The Review provides readers with an accessible overview of the utility, development, and mechanism of action of gold-based small molecules to establish context and basis for the thriving resurgence of gold in medicine.

Recent Advances in 64Cu/67Cu-Based Radiopharmaceuticals

Copper-64 (T_1/2 = 12.7 h) is a positron and beta-emitting isotope, with decay characteristics suitable for both positron emission tomography (PET) imaging and radiotherapy of cancer. Copper-67 (T_1/2 = 61.8 h) is a beta and gamma emitter, appropriate for radiotherapy β-energy and with a half-life suitable for single-photon emission computed tomography (SPECT) imaging. The chemical identities of ⁶⁴Cu and ⁶⁷Cu isotopes allow for convenient use of the same chelating molecules for sequential PET imaging and radiotherapy. A recent breakthrough in ⁶⁷Cu production opened previously unavailable opportunities for a reliable source of ⁶⁷Cu with high specific activity and purity. These new opportunities have reignited interest in the use of copper-containing radiopharmaceuticals for the therapy, diagnosis, and theranostics of various diseases. Herein, we summarize recent (2018-2023) advances in the use of copper-based radiopharmaceuticals for PET, SPECT imaging, radiotherapy, and radioimmunotherapy.

Synthesis and biological evaluation of ruthenium complexes containing phenylseleny against Gram-positive bacterial infection by damage membrane integrity and avoid drug-resistance

Compounds modified with selenium atom as potential antibacterial agents have been exploited to combat the nondrug-resistant bacterial infection. In this study, we designed and synthesized four ruthenium complexes retouching of selenium-ether. Fortunately, those four ruthenium complexes shown excellent antibacterial bioactive (MIC: 1.56-6.25 μg/mL) against Staphylococcus aureus (S. aureus), and the most active complex Ru(II)-4 could kill S. aureus by targeting the membrane integrity and avoid the bacteria to evolve drug resistance. Moreover, Ru(II)-4 was found to significantly inhibit the formation of biofilms and biofilm eradicate capacity. In toxicity experiments, Ru(II)-4 exhibited poor hemolysis and low mammalian toxicity. To illustrate the antibacterial mechanism: we conducted scanning electron microscope (SEM), fluorescent staining, membrane rupture and DNA leakage assays. Those results demonstrated that Ru(II)-4 could destroy the integrity of bacterial cell membrane. Furthermore, both G. mellonella wax worms infection model and mouse skin infection model were established to evaluate the antibacterial activity of Ru(II)-4 in vivo, the results indicated that Ru(II)-4 was a potential candidate for combating S. aureus infections, and almost non-toxic to mouse tissue. Thus, all the results indicated that introducing selenium-atom into ruthenium compounds were a promising strategy for developing interesting antibacterial agents.

Pd(II) Complexes of Chiral Proline-Derived Ligands: Application for Dynamic Thermodynamic Resolution of α-Amino Acids and Their Antibacterial Activities

Novel type of Pd(II) complexes have been synthesized under operationally simple and convenient conditions and applied in the dynamic thermodynamic resolution of racemic N,C-unprotected α-amino acids. After rapid hydrolysis, these Pd(II) complexes produced the corresponding α-amino acids in satisfactory yields and enantioselectivities, accompanied by the recyclable proline-derived ligand. In addition, the method can be readily applied for S/R interconversion to obtain unnatural (R)-α-amino acids from readily available (S)-α-amino acids. Furthermore, biological assays showed that Pd(II) complexes (S,S)-3i and (S,S)-3m exhibited significant antibacterial activities similar to vancomycin, which may represent promising lead structures for further development of antibacterial agents.

New Insights into the Behavior of NHC-Gold Complexes in Cancer Cells

Among the non-platinum antitumor agents, gold complexes have received increased attention owing to their strong antiproliferative effects, which generally occur through non-cisplatin-like mechanisms of action. Several studies have revealed that many cytotoxic gold compounds, such as N-heterocyclic carbene (NHC)-gold(I) complexes, are potent thioredoxin reductase (TrxR) inhibitors. Many other pathways have been supposed to be altered by gold coordination to protein targets. Within this frame, we have selected two gold(I) complexes based on aromatic ligands to be tested on cancer cells. Differently from bis [1,3-diethyl-4,5-bis(4-methoxyphenyl)imidazol-2-ylidene]gold(I) bromide (Au4BC), bis [1-methyl-3-acridineimidazolin-2-ylidene]gold(I) tetrafluoroborate (Au3BC) inhibited TrxR1 activity in vitro. Treatment of Huh7 hepatocellular carcinoma (HCC) cells, and MDA-MB-231 triple-negative breast cancer (TNBC) cells, with Au4BC inhibited cell viability, increased reactive oxygen species (ROS) levels, caused DNA damage, and induced autophagy and apoptosis. Notably, we found that, although Au3BC inhibited TrxR1 activity, no effect on the cell viabilities of HCC and BC cells was observed. At the molecular level, Au3BC induced a protective response mechanism in Huh7 and MDA-MB-231 cells, by inducing up-regulation of RAD51 and p62 protein expression, two proteins involved in DNA damage repair and autophagy, respectively. RAD51 gene knock-down in HCC cells increased cell sensitivity to Au3BC by significant reduction of cell viability, induction of DNA damage, and induction of apoptosis and autophagy. All together, these results suggest that the tested NHC-Gold complexes, Au3BC and Au4BC, showed different mechanisms of action, either dependent or independent of TrxR1 inhibition. As a result, Au3BC and Au4BC were found to be promising candidates as anticancer drugs for the treatment of HCC and BC.

Interaction with bioligands and in vitro cytotoxicity of a new dinuclear dioxido vanadium(V) complex

One centrosymmetric bis(μ-oxido)-bridged vanadium(V) dimer with molecular formula [(V^VO₂)₂(pedf)₂] (1) has been synthesized from the reaction of VOSO₄·5H₂O with a Schiff base ligand (abbreviated with pedf^-) obtained from 2-acetylpyridine and 2-furoic hydrazide in methanol. Complex 1 was characterized by elemental analysis, UV-visible (UV-Vis), Fourier-transform infrared spectra (FT-IR), cyclic voltammetry (CV), electron paramagnetic resonance spectroscopy (EPR) and electrospray ionization-mass spectrometry (ESI-MS) techniques along with single crystal X-ray diffraction (SCXRD). The FT-IR spectral data of 1 indicated the involvement of oxygen and azomethine nitrogen in coordination to the central metal ion. The crystallographic studies revealed a dinuclear oxovanadium(V) complex with the Schiff base coordinated via the ONN donor set with formation of two five-membered chelate rings resulting in a distorted octahedral geometry. The interaction of 1 with calf thymus DNA (CT-DNA) was investigated by spectroscopic measurements and results suggested that the complex binds to CT-DNA via moderate intercalative mode with a binding constant (K_b) around 10³ M^-1. In addition, the in vitro protein binding behavior was studied by fluorescence spectrophotometric method using both bovine serum albumin (BSA) and human serum albumin (HSA) and a static quenching mechanism was observed for the interaction of the complex with both albumins that occurs with a K_b in the range (5-6) × 10³ M^-1. In vitro cytotoxicity of complex 1 on lung cancer cells (A549) and human skin carcinoma cell line (A431) demonstrated that the complex had a broad-spectrum of anti-proliferative activity with IC₅₀ value of 64.2 μM and 56.2 μM.

Multiple and Variable Binding of Pharmacologically Active Bis(maltolato)oxidovanadium(IV) to Lysozyme

The interaction with proteins of metal-based drugs plays a crucial role in their transport, mechanism, and activity. For an active ML_n complex, where L is the organic carrier, various binding modes (covalent and non-covalent, single or multiple) may occur and several metal moieties (M, ML, ML₂, etc.) may interact with proteins. In this study, we have evaluated the interaction of [V^IVO(malt)₂] (bis(maltolato)oxidovanadium(IV) or BMOV, where malt = maltolato, i.e., the common name for 3-hydroxy-2-methyl-4H-pyran-4-onato) with the model protein hen egg white lysozyme (HEWL) by electrospray ionization mass spectrometry, electron paramagnetic resonance, and X-ray crystallography. The multiple binding of different V-containing isomers and enantiomers to different sites of HEWL is observed. The data indicate both non-covalent binding of cis-[VO(malt)₂(H₂O)] and [VO(malt)(H₂O)₃]⁺ and covalent binding of [VO(H₂O)_3–4]²⁺ and cis-[VO(malt)₂] and other V-containing fragments to the side chains of Glu35, Asp48, Asn65, Asp87, and Asp119 and to the C-terminal carboxylate. Our results suggest that the multiple and variable interactions of potential V^IVOL₂ drugs with proteins can help to better understand their solution chemistry and contribute to define the molecular basis of the mechanism of action of these intriguing molecules.

The interaction of [V^IVO(malt)₂] (BMOV, malt = maltolato) with hen egg white lysozyme (HEWL) reveals the multiple binding of different V-containing isomers and enantiomers to different sites and non-covalent and covalent binding of cis-[VO(malt)₂(H₂O)], [VO(malt)(H₂O)₃]⁺, [VO(H₂O)₃₋₄]²⁺, and cis-[VO(malt)₂] to Glu, Asp, and Asn residues.

Metal Complexes as DNA Synthesis and/or Repair Inhibitors: Anticancer and Antimicrobial Agents

Medicinal inorganic chemistry involving the utilization of metal-based compounds as therapeutics has become a field showing distinct promise. DNA and RNA are ideal drug targets for therapeutic intervention in the case of various diseases, such as cancer and microbial infection. Metals play a vital role in medicine, with at least 10 metals known to be essential for human life and a further 46 nonessential metals having been involved in drug therapies and diagnosis. These metal-based complexes interact with DNA in various ways, and are often delivered as prodrugs which undergo activation in vivo. Metal complexes cause DNA crosslinking, leading to the inhibition of DNA synthesis and repair. In this review, the various interactions of metal complexes with DNA nucleic acids, as well as the underlying mechanism of action, were highlighted. Furthermore, we also discussed various tools used to investigate the interaction between metal complexes and the DNA. The tools included in vitro techniques such as spectroscopy and electrophoresis, and in silico studies such as protein docking and density-functional theory that are highlighted for preclinical development.

In Vitro Anti-SARS-CoV-2 Activity of Selected Metal Compounds and Potential Molecular Basis for Their Actions Based on Computational Study

Metal-based drugs represent a rich source of chemical substances of potential interest for the treatment of COVID-19. To this end, we have developed a small but representative panel of nine metal compounds, including both synthesized and commercially available complexes, suitable for medical application and tested them in vitro against the SARS-CoV-2 virus. The screening revealed that three compounds from the panel, i.e., the organogold(III) compound Aubipyc, the ruthenium(III) complex KP1019, and antimony trichloride (SbCl₃), are endowed with notable antiviral properties and an acceptable cytotoxicity profile. These initial findings prompted us to perform a computational study to unveil the likely molecular basis of their antiviral actions. Calculations evidenced that the metalation of nucleophile sites in SARS-CoV-2 proteins or nucleobase strands, induced by Aubipyc, SbCl₃, and KP1019, is likely to occur. Remarkably, we found that only the deprotonated forms of Cys and Sec residues can react favorably with these metallodrugs. The mechanistic implications of these findings are discussed.