Water-Soluble Dioxidovanadium(V) Complexes of Aroylhydrazones: DNA/BSA Interactions, Hydrophobicity, and Cell-Selective Anticancer Potential

Vanadium(V) complexes derived from triphenylphosphonium and hydrazides: cytotoxicity evaluation and interaction with biomolecules

The development of coordination compounds with antineoplastic therapeutic properties is currently focused on non-covalent interactions with deoxyribonucleic acid (DNA). Additionally, the interaction profiles of these compounds with globular plasma proteins, particularly serum albumin, warrant thorough evaluation. In this study, we report on the interactions between biomolecules and complexes featuring hydrazone-type imine ligands coordinated with vanadium. The potential to enhance the therapeutic efficiency of these compounds through mitochondrial targeting is explored. This targeting is facilitated by the derivatization of ligands with triphenylphosphonium groups. Thus, this work presents the synthesis, characterization, interactions, and cytotoxicity of dioxidovanadium(V) complexes (C1-C5) with a triphenylphosphonium moiety. These VV-species are coordinated to hydrazone-type iminic ligands derived from (3-formyl-4-hydroxybenzyl)triphenylphosphonium chloride ([AH]Cl) and aromatic hydrazides ([H2L1]Cl-[H2L5]Cl). The structures of the five complexes were elucidated through single-crystal X-ray diffraction and vibrational spectroscopies, confirming the presence of dioxidovanadium(V) species in various geometries with degrees of distortion (τ = 0.03-0.50) and highlighting their zwitterionic characteristics. The molecular structural stability of C1-C5 in solution was ascertained using 1H, 19F, 31P, and 51V-nuclear magnetic resonance. Moreover, their interactions with biomolecules were evaluated using diverse spectroscopic methodologies and molecular docking, indicating moderate interactions (Kb ≈ 104 M-1) with calf thymus DNA in the minor groove and with human serum albumin, predominantly in the superficial IB subdomain. Lastly, the cytotoxic potentials of these complexes were assessed in keratinocytes of the HaCaT lineage, revealing that C1-C5 induce a reduction in metabolic activity and cell viability through apoptotic pathways.

Monomeric copper(II) complexes with unsymmetrical salen environment: Synthesis, characterization and study of biological activities

Three new ONNO-donor tetradentate unsymmetrical salen ligands were synthesized by using o-phenyl diamine with substituted salicylaldehydes followed by a two-step reaction methodology. These three ligands by reaction with Cu(OAc)2.4H2O produced three new monomeric Cu(II) complexes, [CuII(L1-3)] (1-3). Elemental analysis, IR, UV-vis, NMR, and HR-ESI-MS techniques were used to analyze and characterize all the synthesized ligands and their corresponding metal complexes. Molecular structures of 1-3 were confirmed by the single-crystal-XRD analysis. Furthermore, the DNA binding ability of these complexes was checked through UV-vis, fluorescence spectroscopy, and also by circular dichroism studies. All the complexes were found to show an intercalation mode of binding with the Kb value in the range of 104-105 M-1. Finally, 1-3 was tested against two malignant (HeLa and A549) and non-cancerous (NIH-3T3) cell lines to check their in vitro antiproliferative activities. Among all, 1 is the most cytotoxic of the series having IC50 values of 5.7 ± 0.9 and 6.0 ± 0.3 μM against HeLa and A549 cell lines, respectively. This result is also consistent with the DNA binding order. Furthermore, the apoptotic mode of cell death of all the complexes was also evaluated by DAPI, AO/EB, and Annexin V-FITC/PI double staining assays.

Hydrolytically Stable TiIV-Hydrazone-Based Metallodrugs: Protein Interaction and Anticancer Potential

In this work, three titanium(IV) [TiIV(L1-3)2] (1-3) complexes have been reported using three different tridentate dibasic ONO donor hydrazone ligands, pyridine-4-carboxylic acid (3-ethoxy-2-hydroxybenzylidene)-hydrazide (H2L1), furan-2-carboxylic acid (3-ethoxy-2-hydroxybenzylidene)-hydrazide (H2L2), and thiophene-2-carboxylic acid (3-ethoxy-2-hydroxybenzylidene)-hydrazide (H2L3) tethered with heterocyclic moieties. Elemental analysis, FT-IR, UV-vis, NMR, HR-ESI-MS, and single-crystal X-ray analysis have been used to characterize H2L1-3 and 1-3. In solid structures of 1-3, two ligand molecules with N2O4 donor sets give distorted octahedral geometries to the metal center. The aqueous stability of 1-3 was investigated and well correlated to their perceived pharmacological results. During the investigation, all three complexes were found to be hydrolytically stable in a 90% DMSO-d6/10% D2O (v/v) medium up to 48 h. Furthermore, the interaction of 1-3 with bovine serum albumin (BSA) was tested using fluorescence and absorption techniques. The complexes showed static quenching with a biomolecular quenching constant of Kq ∼ 1013 proposing a high affinity of complexes for BSA. Finally, the anticancer potential of 1-3 was tested against HeLa, A549, and NIH-3T3 cell lines. Among all, 1 with an IC50 value of 11.6 ± 1.1 μM against HeLa cells was found to be the most cytotoxic in the series. Furthermore, it has been found that the compounds induce an apoptotic mode of cell death, which is confirmed by the live cell confocal microscopy and flow cytometry techniques.

Exploring the antioxidant, antimicrobial, cytotoxic and biothermodynamic properties of novel morpholine derivative bioactive Mn(ii), Co(ii) and Ni(ii) complexes - combined experimental and theoretical measurements towards DNA/BSA/SARS-CoV-2 3CLPro

A novel class of bioactive complexes (1-3) [MII(L)2(bpy)], where, L = 2-(4-morpholinobenzylideneamino)phenol, bpy = 2,2'-bipyridine, MII = Mn (1), Co (2) or Ni (3), were assigned to octahedral geometry based on analytical and spectral measurements. Gel electrophoresis showed that complex (2) demonstrated significant DNA cleavage activity compared to the other complexes under the action of oxidation agent (H2O2). The DNA binding constant properties measured by various techniques were in the following sequence: (2) > (3) > (1) > (HL), which suggests that the complexes might intercalate DNA, a possibility that is also supported by their biothermodynamic characteristics. The binding constant results for BSA from electronic absorption and fluorometric titrations demonstrate that complex (2) exhibits the highest binding effectiveness among them all, which means that all the compounds could interact with BSA through a static approach, additionally supported by FRET measurements. DFT and docking calculations were employed to realize the electronic structure, reactivity, and interaction capability of all substances with DNA, BSA, and the SARS-CoV-2 main protease. These binding energies fell within the ranges -7.7 to -8.5, -8.2 to -10.1 and -6.7 to -9.3 kcal mol-1, respectively. The higher reactivity of the complexes than the ligand is supported by FMO theory. The in vitro antibacterial, cytotoxicity, and radical scavenging characteristics revealed that complexes (2-3) have better biological efficacy than the others. The cytotoxicity and binding properties also show good correlation with the partition coefficient (log P), which is encouraging because all of the experimental findings are closely correlated with the theoretical measurements.

A Series of Non-Oxido VIV Complexes of Dibasic ONS Donor Ligands: Solution Stability, Chemical Transformations, Protein Interactions, and Antiproliferative Activity

A series of mononuclear non-oxido vanadium(IV) complexes, [V^IV(L^1-4)₂] (1-4), featuring tridentate bi-negative ONS chelating S-alkyl/aryl-substituted dithiocarbazate ligands H₂L^1-4, are reported. All the synthesized non-oxido V^IV compounds are characterized by elemental analysis, spectroscopy (IR, UV-vis, and EPR), ESI-MS, as well as electrochemical techniques (cyclic voltammetry). Single-crystal X-ray diffraction studies of 1-3 reveal that the mononuclear non-oxido V^IV complexes show distorted octahedral (1 and 2) or trigonal prismatic (3) arrangement around the non-oxido V^IV center. EPR and DFT data indicate the coexistence of mer and fac isomers in solution, and ESI-MS results suggest a partial oxidation of [V^IV(L^1-4)₂] to [V^V(L^1-4)₂]⁺ and [V^VO₂(L^1-4)]^-; therefore, all these three complexes are plausible active species. Complexes 1-4 interact with bovine serum albumin (BSA) with a moderate binding affinity, and docking calculations reveal non-covalent interactions with different regions of BSA, particularly with Tyr, Lys, Arg, and Thr residues. In vitro cytotoxic activity of all complexes is assayed against the HT-29 (colon cancer) and HeLa (cervical cancer) cells and compared with the NIH-3T3 (mouse embryonic fibroblast) normal cell line by MTT assay and DAPI staining. The results suggest that complexes 1-4 are cytotoxic in nature and induce cell death in the cancer cell lines by apoptosis and that a mixture of V^IV, V^V, and V^VO₂ species could be responsible for the biological activity.

Vanadium(IV) complexes of salicylaldehyde-based furoic acid hydrazones: Synthesis, BSA binding and in vivo antidiabetic potential

Solution synthesis afforded five novel neutral heteroleptic octahedral paramagnetic mononuclear oxidovanadium(IV) complexes of general composition [VO(bpy)L], where L is a dianionic tridentate ONO-donor hydrazone ligand derived from 2-furoic acid hydrazide and salicylaldehyde and its 5-substituted derivatives. Characterization was carried out by elemental analysis, mass spectrometry, infrared, electron, NMR, and EPR spectroscopy, cyclic voltammetry and conductometry. The molecular and crystal structure of the complex with 5-chloro-salicylaldehyde 2-furoic acid hydrazone (2) was determined. The quantum chemical properties of the vanadium complexes were studied at B3LYP and M062X levels with the lanl2dz basis set using Gaussian. Additionally, Swiss-ADME analysis was performed and complex (4), featuring a 5-nitro substituent on the hydrazone ligand, was selected for further investigation. The effects of the in vivo application of the complex on selected biochemical parameters in healthy and diabetic Wistar rats were investigated. Strong antidiabetic effect associated with moderate hypoalbuminemia was observed. Furthermore, the interaction of complexes with BSA was studied by spectrofluorimetry. A significant conformational change of BSA in the presence of vanadium complexes was found. Synchronous fluorescence spectra revealed significant changes in the tyrosine microenvironment of BSA. The FRET analysis was also used and the non-radiative process of energy transfer is elucidated. Thermodynamic data suggest van der Waals forces and hydrogen bonding as predominant binding modes of complexes to BSA.

Affinity Studies of Hemicyanine Derived Water Soluble Colorimetric Probes with Reactive Oxygen/Nitrogen/Sulfur Species

Peroxynitrite (ONOO^- ) is an essential endogenous reactive oxygen species (ROS) generated in mitochondria under various pathological and physiological conditions. An increase in its level in mitochondria is related to numerous diseases. Herein, we report a series of hemicyanine-derived water-soluble colorimetric probes (1-4) and the reactivity of which was studied with various reactive oxygen, nitrogen, and sulfur species. Probes 1-4 are formed by conjugating 1,2,3,3-tetramethyl-3H-indolium iodide and 4-hydroxybenzaldehyde or its derivatives through an alkene linkage formed by the Knoevenagel reaction. Oxidative cleavage of the electron-rich double bond of the conjugated hemicyanine dye revealed a discerning affinity of probe 3 towards peroxynitrite among all reactive oxygen species. The rapid change in color of 3 provides a sensitive and selective method for detecting peroxynitrite with a low detection limit of 180 nM. Notably, the water solubility of the probe displays excellent performance for the selective detection of peroxynitrite among ROS and reactive nitrogen (RNS)/sulfur species (RSS). UV-vis, ¹ H NMR, and ¹³ C NMR spectroscopic data and results from theoretical calculations provide further information on the interaction of peroxynitrite with probe 3.

A Vanadium(V) complexes derived from pyridoxal/salicylaldehyde. Interaction with CT-DNA/HSA, and molecular docking assessments

With the increasing development of metallopharmaceuticals, coordination compounds become viable alternatives for therapeutic uses. Despite the importance of platinum derivatives in this area, first-row transition metals complexes are welcome due to their characteristics. Vanadium is a promising metal in this context, as it has a range of compounds with different biological applications, including anticancer therapeutic effects. In this effort, the study of interactions between coordination compounds with deoxyribonucleic acid and with human serum albumin is fundamental. In this way, ten iminic ligands were synthesized by condensing p-substituted aromatic benzohydrazides (OH, CH₃, H, NO₂, and NH₂) with salicylaldehyde (L1As-L5As) or pyridoxal hydrochloride (L1P-L5P). These ligands have characteristics that allow the tridentate coordination of vanadium cations, leading to the formation of ten vanadium(V) complexes (C1As-C5As and C1P-C5P) with different structural features, all characterized by single-crystal X-ray diffraction, UV-Vis and infrared spectroscopies, and cyclic voltammetry. In addition, the complexes were tested for their interactions with calf thymus deoxyribonucleic acid and human serum albumin by spectroscopic assays and molecular docking calculations. These new results can contribute to further research and provide different ways to design new vanadium complexes with biological applications.

Ruthenium(II)-Dithiocarbazates as Anticancer Agents: Synthesis, Solution Behavior, and Mitochondria-Targeted Apoptotic Cell Death

The reaction of the Ru(PPh₃ )₃ Cl₂ with HL^1-3 -OH (-OH stands for the oxime hydroxyl group; HL¹ -OH=diacetylmonoxime-S-benzyldithiocarbazonate; HL² -OH=diacetylmonoxime-S-(4-methyl)benzyldithiocarbazonate; and HL³ -OH=diacetylmonoxime-S-(4-chloro)benzyl-dithiocarbazonate) gives three new ruthenium complexes [Ru^II (L^1-3 -H)(PPh₃ )₂ Cl] (1-3) (-H stands for imine hydrogen) coordinated with dithiocarbazate imine as the final products. All ruthenium(II) complexes (1-3) have been characterized by elemental (CHNS) analyses, IR, UV-vis, NMR (¹ H, ¹³ C, and ³¹ P) spectroscopy, HR-ESI-MS spectrometry and also, the structure of 1-2 was further confirmed by single crystal X-ray crystallography. The solution/aqueous stability, hydrophobicity, DNA interactions, and cell viability studies of 1-3 against HeLa, HT-29, and NIH-3T3 cell lines were performed. Cell viability results suggested 3 being the most cytotoxic of the series with IC₅₀ 6.9±0.2 μM against HeLa cells. Further, an apoptotic mechanism of cell death was confirmed by cell cycle analysis and Annexin V-FITC/PI double staining techniques. In this regard, the live cell confocal microscopy results revealed that compounds primarily target the mitochondria against HeLa, and HT-29 cell lines. Moreover, these ruthenium complexes elevate the ROS level by inducing mitochondria targeting apoptotic cell death.

Mitochondria-Targeted Luminescent Organotin(IV) Complexes: Synthesis, Photophysical Characterization, and Live Cell Imaging

Five fluorescent ONO donor-based organotin(IV) complexes, [Sn^IV(L^1-5)Ph₂] (1-5), were synthesized by the one-pot reaction method and fully characterized spectroscopically including the single-crystal X-ray diffraction studies of 2-4. Detailed photophysical characterization of all compounds was performed. All the compounds exhibited high luminescent properties with a quantum yield of 17-53%. Additionally, the results of cellular permeability analysis suggest that they are lipophilic and easily absorbed by cells. Confocal microscopy was used to examine the live cell imaging capability of 1-5, and the results show that the compounds are mostly internalized in mitochondria and exhibit negligible cytotoxicity at imaging concentration. Also, 1-5 exhibited high photostability as compared to the commercial dye and can be used in long-term real-time tracking of cell organelles. Also, it is found that the probes (1-5) are highly tolerable during the changes in mitochondrial morphology. Thus, this kind of low-toxic organotin-based fluorescent probe can assist in imaging of mitochondria within living cells and tracking changes in their morphology.

Mixed Ni(II) and Co(II) complexes of nalidixic acid drug: Synthesis, characterization, DNA/BSA binding profile and in vitro cytotoxic evaluation against MDA-MB-231 and HepG2 cancer cell lines

In this work, herein we report the synthesis, structural characterization and in vitro cytotoxic evaluation of two mixed Co(II)/Ni(II)-nalidixic acid-bipyridyl complexes (1 and 2). The structural analysis of metal complexes 1 and 2 was carried out by analytical and multispectroscopic techniques (FT-IR, UV-vis, EPR, sXRD). The crystallographic details of complexes 1 and 2 revealed a monoclinic crystal system with P21/c space group. DFT studies of complexes were performed to get electronic structure and localization of HOMO and LUMO electron densities. Hirshfeld surface analysis of metal complexes 1 and 2 was employed to understand the various intermolecular interactions (C-H···O, N-H···H and O-H···O) that define the stability of crystal lattice structures. The comparative interaction studies of complex 1 and complex 2 with DNA/BSA were performed by diverse multispectroscopic and analytical techniques to evaluate their chemotherapeutic potential. The magnitude of the DNA binding propensity and binding mode was verified by calculating K_b, K and K_sv values. Higher binding affinity was observed in case of complex 2via intercalative mode. Furthermore, the cytotoxic assessment of complexes 1 and 2 was examined against MDA-MB-231 (triple negative human breast cancer cell line) and HepG2 (liver carcinoma cell line) employing MTT assay which revealed remarkably effecient and specific cytotoxic activity of complex 2.