New Vanadium(V) Complexes with Salicylaldehyde Semicarbazone Derivatives: Synthesis, Characterization, and in vitro Insulin-Mimetic Activity− Crystal Structure of [VvO2(salicylaldehyde semicarbazone)]

Synthesis, Characterization, PXRD Studies, Theoretical Calculation, and Antitumor Potency Studies of a Novel N,O-Multidentate Chelating Ligand and Its Zr(IV), V(IV), Ru(III), and Cd(II) Complexes

A new series of Zr(IV), V(IV), Ru(III), and Cd(II) complexes with the ligand N-((5-hydroxy-4-oxo-4H-pyran-3-yl)methylene)-2-(p-tolylamino)acetohydrazide (H2L) have been prepared. FT-IR, 1H-NMR, electronic spectra, powder X-ray, and thermal behavior methods were applied to elucidate the structural composition of new compounds. Geometry optimization for all synthesized compounds was conducted using the Gaussian09 program via the DFT method, to obtain optimal structures and essential parameters. Moreover, the antibacterial and antitumor activity of the ligand and its complexes were studied, where the Cd(II) complex acquires probably the best antibacterial activity followed by the Ru(III) complex towards bacterial species than others when using ampicillin and gentamicin were used as standard drugs. The complexes exhibited interestingly antitumor potential against the MCF-7 breast cancer cell line. The cytotoxicity of the new complexes has been arranged to follow the order: Ru(III) complex > Cd(II) complex > Zr(IV) complex > V(IV) complex > ligand. Molecular docking was performed on the active site of ribosyltransferase and obtained good results. Structure-based molecular docking is used to identify a potential therapeutic inhibitor for NUDT5.

A family of amphiphilic dioxidovanadium(V) hydrazone complexes as potent carbonic anhydrase inhibitors along with anti-diabetic and cytotoxic activities

A family of dioxidovanadium(V) complexes (1-4) of the type [Na(H₂O)_x]⁺[V^VO₂(HL^1-4)]^- (x = 4, 4.5 and 7) where HL^2- represents the dianionic form of 2-hydroxybenzoylhydrazone of 2-hydroxyacetophenone (H₂L¹, complex 1), 2-hydroxy-5-methylacetophenone (H₂L², complex 2), 2-hydroxy-5-methoxyacetophenone (H₂L³, complex 3) and 2-hydroxy-5-chloroacetophenone (H₂L⁴, complex 4), have been synthesized and characterized by analytical and spectral methods. These complexes exhibited the potential abilities to suppress the erythrocytes carbonic anhydrase enzymatic activity in type 1 and type 2 diabetic patients (in vitro), promising antidiabetic activity against T2 diabetic mice (in vivo). They also exhibited significant cytotoxic activity against cervical cancer (SiHa) cells (in vitro) as the IC₅₀ value of complexes 1, 2 and 4 is substantially lower than the value found for cisplatin while that of 3 is comparable and follow the order: 4 < 1 < 2 < 3 and can kill the cells by apoptosis via the generation of reactive oxygen species (ROS). The complexes are soluble both in water and octanol media and also non-toxic at working concentrations. The antidiabetic activity of these four complexes follows the order: 4 > 2 > 1 > 3 while both the carbonic anhydrase and cytotoxic activity follow the order: 4 > 1 > 2 > 3 suggesting that complex 4, containing electron withdrawing Cl atom is the most reactive while 3 with electron donating OCH₃ group is the least reactive species. The molecular docking study on hCA-I and hCA-II demonstrates that complexes interact via hydrogen bonding as well as different types of π-stacking.

Effective topical treatments of innovative NNO-tridentate vanadium (IV) complexes-mediated photodynamic therapy in psoriasis-like mice model

Psoriasis is a chronic inflammatory skin disease that can significantly impact the quality of human life. Various drug treatments with long-term severe side effects limit those drugs usage. Photodynamic therapy...

Heteroleptic Oxidovanadium(V) Complexes with Activity against Infective and Non-Infective Stages of Trypanosoma cruzi

Five heteroleptic compounds, [VVO(IN-2H)(L-H)], where L are 8-hydroxyquinoline derivatives and IN is a Schiff base ligand, were synthesized and characterized in both the solid and solution state. The compounds were evaluated on epimastigotes and trypomastigotes of Trypanosoma cruzi as well as on VERO cells, as a mammalian cell model. Compounds showed activity against trypomastigotes with IC50 values of 0.29-3.02 μM. IN ligand and the new [VVO2(IN-H)] complex showed negligible activity. The most active compound [VVO(IN-2H)(L2-H)], with L2 = 5-chloro-7-iodo-8-hydroxyquinoline, showed good selectivity towards the parasite and was selected to carry out further biological studies. Stability studies suggested a partial decomposition in solution. [VVO(IN-2H)(L2-H)] affects the infection potential of cell-derived trypomastigotes. Low total vanadium uptake by parasites and preferential accumulation in the soluble proteins fraction were determined. A trypanocide effect was observed when incubating epimastigotes with 10 × IC50 values of [VVO(IN-2H)(L2-H)] and the generation of ROS after treatments was suggested. Fluorescence competition measurements with DNA:ethidium bromide adduct showed a moderate DNA interaction of the complexes. In vivo toxicity study on C. elegans model showed no toxicity up to a 100 μM concentration of [VVO(IN-2H)(L2-H)]. This compound could be considered a prospective anti-T. cruzi agent that deserves further research.

Are vanadium complexes druggable against the main protease Mpro of SARS-CoV-2? - A computational approach

In silico techniques helped explore the binding capacities of the SARS-CoV-2 main protease (M^pro) for a series of metalloorganic compounds. Along with small size vanadium complexes a vanadium-containing derivative of the peptide-like inhibitor N3 (N-[(5-methylisoxazol-3-yl)carbonyl]alanyl-l-valyl-N1-((1R,2Z)-4-(benzyloxy)-4-oxo-1-{[(3R)-2-oxopyrrolidin-3-yl] methyl }but-2-enyl)-l-leucinamide) was designed from the crystal structure with PDB entry code 6LU7. On theoretical grounds our consensus docking studies evaluated the binding affinities at the hitherto known binding site of Chymotrypsin-like protease (3CLpro) of SARS-CoV-2 for existing and designed vanadium complexes. This main virus protease (M^pro) has a Cys-His dyad at the catalytic site that is characteristic of metal-dependent or metal-inhibited hydrolases. M^pro was compared to the human protein-tyrosine phosphatase 1B (hPTP1B) with a comparable catalytic dyad. HPTP1B is a key regulator at an early stage in the signalling cascade of the insulin hormone for glucose uptake into cells. The vanadium-ligand binding site of hPTP1B is located in a larger groove on the surface of M^pro. Vanadium constitutes a well-known phosphate analogue. Hence, its study offers possibilities to design promising vanadium-containing binders to SARS-CoV-2. Given the favourable physicochemical properties of vanadium nuclei, such organic vanadium complexes could become drugs not only for pharmacotherapy but also diagnostic tools for early infection detection in patients. This work presents the in silico design of a potential lead vanadium compound. It was tested along with 20 other vanadium-containing complexes from the literature in a virtual screening test by docking to inhibit M^pro of SARS-CoV-2.

Chemistry of mixed-ligand oxidovanadium(IV) complexes of aroylhydrazones incorporating quinoline derivatives: Study of solution behavior, theoretical evaluation and protein/DNA interaction

A series of eight hexacoordinated mixed-ligand oxidovanadium(IV) complexes [VO(L^x)(L^N-N)] (1-8), where L^x = L¹ - L⁴ are four differently substituted ONO donor aroylhydrazone ligands and L^N-N are N,N-donor bases like 2,2'-bipyridine (bipy) (1, 3, 5 and 7) and 1,10-phenanthroline (phen) (2, 4, 6 and 8), have been reported. All synthesized complexes have been characterized by various physicochemical techniques and molecular structures of 1 and 6 were determined by X-ray crystallography. With a view to evaluate the biological activity of the V^IVO species, the behavior of the systems V^IVO²⁺/L^x, V^IVO²⁺/L^x/bipy and V^IVO²⁺/L^x/phen was studied as a function of pH in a mixture of H₂O/DMSO 50/50 (v/v). DFT calculations allowed finding out the relative stability of the tautomeric forms of the ligands, and predicting the structure of vanadium complexes and their EPR parameters. To study their interaction with proteins, firstly the ternary systems V^IVO²⁺/L^1,2 with 1-methylimidazole, which is a good model for histidine binding, were examined. Subsequently the interaction of the complexes with lysozyme (Lyz), cytochrome c (Cyt) and bovine serum albumin (BSA) was studied. The results indicate that the complexes showed moderate binding affinity towards BSA, while no interaction takes place with lysozyme and cytochrome c. This could be explained with the higher number of accessible coordinating and polar residues for BSA than for Lyz and Cyt. Further, the complexes were also evaluated for their DNA binding propensity through UV-vis absorption titration and fluorescence spectral studies. These results were consistent with BSA binding affinity and showed moderate binding affinity towards CT-DNA.

Synthesis, structure and biological evaluation of mixed ligand oxidovanadium(iv) complexes incorporating 2-(arylazo)phenolates

Synthesis and characterization of mixed ligand oxidovanadium(iv) complexes [V^IVO(L^1–4)(L^NN)] incorporating arylazo ligands: evaluation of DNA/BSA interaction and cytotoxicity activity.

Synthesis, structure, solution behavior, reactivity and biological evaluation of oxidovanadium(iv/v) thiosemicarbazone complexes

The synthesis and characterization of an oxidovanadium(iv) [VIVO(L)(acac)] (1) and of two dioxidovanadium(v) [VVO2(L')] (2) and [VVO2(L)] (2a) complexes of the Schiff base formed from the reaction of 4-(p-fluorophenyl) thiosemicarbazone with pyridine-2-aldehyde (HL) are described. The oxidovanadium(iv) species [VIVO(L)(acac)] (1) was synthesized by the reaction of VIVO(acac)2 with the thiosemicarbazone HL in refluxing ethanol. The recrystallization of [VIVO(L)(acac)] (1) in DMF, CH3CN or EtOH gave the same product i.e. the dioxidovanadium(v) complex [VVO2(L)] (2a); however, upon recrystallization of 1 in DMSO a distinct compound [VVO2(L')] (2) was formed, wherein the original ligand L- is transformed to a rearranged one, L'-. In the presence of DMSO the ligand in complex 1 is found to undergo methylation at the carbon centre attached to imine nitrogen (aldimine) and transformed to the corresponding VVO2-species through in situ reaction. The synthesized HL and the metal complexes were characterized by elemental analysis, IR, UV-Vis, NMR and EPR spectroscopy. The molecular structure of [VVO2(L')] (2) was determined by single crystal X-ray crystallography. The methylation of various other ligands and complexes prepared from different vanadium precursors under similar reaction conditions was also attempted and it was confirmed that the imine methylation observed is both ligand and metal precursor specific. Complexes 1 and 2 show in vitro insulin-like activity against insulin responsive L6 myoblast cells, higher than VIVO(acac)2, with complex 1 being more potent. In addition, the in vitro cytotoxicity studies of HL, and of complexes 1 and 2 against the MCF-7 and Vero cell lines were also done. The ligand is not cytotoxic and complex 2 is significantly more cytotoxic than 1. DAPI staining experiments indicate that an increase in the time of incubation and an increase of concentration of the complexes lead to the increase in cell death.

Chemistry of Monomeric and Dinuclear Non-Oxido Vanadium(IV) and Oxidovanadium(V) Aroylazine Complexes: Exploring Solution Behavior

A series of mononuclear non-oxido vanadium(IV) [V(IV)(L(1-4))2] (1-4), oxidoethoxido vanadium(V) [V(V)O(L(1-4))(OEt)] (5-8), and dinuclear μ-oxidodioxidodivanadium(V) [V(V)2O3(L(1))2] (9) complexes with tridentate aroylazine ligands are reported [H2L(1) = 2-furoylazine of 2-hydroxy-1-acetonaphthone, H2L(2) = 2-thiophenoylazine of 2-hydroxy-1-acetonaphthone, H2L(3) = 1-naphthoylazine of 2-hydroxy-1-acetonaphthone, H2L(4) = 3-hydroxy-2-naphthoylazine of 2-hydroxy-1-acetonaphthone]. The complexes are characterized by elemental analysis, by various spectroscopic techniques, and by single-crystal X-ray diffraction (for 2, 3, 5, 6, 8, and 9). The non-oxido V(IV) complexes (1-4) are quite stable in open air as well as in solution, and DFT calculations allow predicting EPR and UV-vis spectra and the electronic structure. The solution behavior of the [V(V)O(L(1-4))(OEt)] compounds (5-8) is studied confirming the formation of at least two different types of V(V) species in solution, monomeric corresponding to 5-8, and μ-oxidodioxidodivanadium [V(V)2O3(L(1-4))2] compounds. The μ-oxidodioxidodivanadium compound [V(V)2O3(L(1))2] (9), generated from the corresponding mononuclear complex [V(V)O(L(1))(OEt)] (5), is characterized in solution and in the solid state. The single-crystal X-ray diffraction analyses of the non-oxido vanadium(IV) compounds (2 and 3) show a N2O4 binding set and a trigonal prismatic geometry, and those of the V(V)O complexes 5, 6, and 8 and the μ-oxidodioxidodivanadium(V) (9) reveal that the metal center is in a distorted square pyramidal geometry with O4N binding sets. For the μ-oxidodioxidodivanadium species in equilibrium with 5-8 in CH2Cl2, no mixed-valence complexes are detected by chronocoulometric and EPR studies. However, upon progressive transfer of two electrons, two distinct monomeric V(IV)O species are detected and characterized by EPR spectroscopy and DFT calculations.

A study of DNA/BSA interaction and catalytic potential of oxidovanadium(v) complexes with ONO donor ligands

The study of DNA/BSA interaction and the catalytic potential of five mono- and dinuclear oxidoethoxido vanadium(v) complexes.

(2E)-2-(3-Ethoxy-2-hydroxybenzylidene)hydrazinecarboxamide

The title compound, C₁₀H₁₃N₃O₃, adopts an E conformation with respect to the azomethine bond and crystallizes in the amide form. A classical intra­molecular O—H⋯N hydrogen bond is present. The two N atoms of the hydrazinecarboxamide unit are also involved in inter­molecular N—H⋯O hydrogen bonds, with the O atom of the hydrazinecarboxamide group acting as the acceptor. Pairs of N—H⋯O hydrogen bond link the mol­ecules into centrosymmetric dimers, which are linked by further N—H⋯O hydrogen bonds into chains along the b axis. The chains are linked by C—H⋯π inter­actions.

Synthesis and In Vitro Antitumor Activity of Two Mixed-Ligand Oxovanadium(IV) Complexes of Schiff Base and Phenanthroline

Two oxovanadium(IV) complexes of [VO(msatsc)(phen)], (1) (msatsc = methoxylsalicylaldehyde thiosemicarbazone, phen = phenanthroline) and its novel derivative [VO (4-chlorosatsc)(phen)], (2) (4-chlorosatsc = 4-chlorosalicylaldehyde thiosemicarbazone), have been synthesized and characterized by elemental analysis, IR, ES-MS, (1)H NMR, and magnetic susceptibility measurements. Their antitumor effects on BEL-7402, HUH-7, and HepG2 cells were studied by MTT assay. The antitumor biological mechanism of these two complexes was studied in BEL-7402 cells by cell cycle analysis, Hoechst 33342 staining, Annexin V-FITC/PI assay, and detection of mitochondrial membrane potential (ΔΨm). The results showed that the growth of cancer cells was inhibited significantly, and complexes 1 and 2 mainly caused in BEL-7402 cells G0/G1 cell cycle arrest and induced apoptosis. Both 1 and 2 decreased significantly the ΔΨm, causing the depolarization of the mitochondrial membrane. Complex 2 showed greater antitumor efficiency than that of complex 1.

Structure and spectral properties of dinuclear zinc complex containing semicarbazonate ligands

The dinuclear Zn(2+) complex [Zn(HSSC)OAc](2)·2DMF (H(2)SSC=salicylaldehyde semicarbazone; HOAc=acetic acid; DMF=N,N-dimethylfomamide) was prepared and structurally characterized by single crystal X-ray. The basic structural unit of the complex is a dinuclear complex [Zn(HSSC)OAc](2) in which the semicarbazone ligand adopts the phenol-imine form. The deprotonated phenol group forms a one-atom bridge between the two zinc centers, and both of the zinc centers are five-coordinated. The local coordination environment of Zn(2+) can be approximately considered as square pyramidal. UV spectral studies show that the H(2)SSC provides strong binding of Zn(2+) in a 1:1 ratio in solution. The conditional binding constant of the complex is lgK(Zn-L)=12.89±0.76 in 0.05M Tris-HCl buffer at pH 7.4. The H(2)SSC exhibits an enhanced fluorescence effect by the addition of Zn(2+), and affords an excellent selectivity for Zn(2+) under physiological conditions.

Vanadium polypyridyl compounds as potential antiparasitic and antitumoral agents: new achievements

In the search for new therapeutic tools against diseases produced by kinetoplastid parasites five vanadyl complexes, [V(IV)O(L-2H)(phen)], including 1,10-phenanthroline (phen) and tridentate salicylaldehyde semicarbazone derivatives as ligands have been synthesized and characterized in the solid state and in solution by using different techniques. EPR suggested a distorted octahedral geometry with the tridentate semicarbazone occupying three equatorial positions and phen coordinated in an equatorial/axial mode. The compounds were evaluated in vitro on epimastigotes of Trypanosoma cruzi, causative agent of Chagas disease, Leishmania panamensis and Leishmania chagasi and on tumor cells. The complexes showed higher in vitro anti-trypanosomal activities than the reference drug Nifurtimox (IC(50) values in the range 1.6-3.8 μM) and increased activities in respect to the free semicarbazone ligands. In vitro activity on promastigote and amastigote forms of Leishmania showed interesting results. The compounds [VO(L1-2H)(phen)] and [VO(L3-2H)(phen)], where L1 = 2-hydroxybenzaldehyde semicarbazone and L3 = 2-hydroxy-3-methoxybenzaldehyde semicarbazone, resulted active (IC(50) 2.74 and 2.75 μM, respectively, on promastigotes of L. panamensis; IC(50) 19.52 and 20.75 μM, respectively, on intracellular amastigotes of L. panamensis) and showed low toxicity on THP-1 mammalian cells (IC(50) 188.55 and 88.13 μM, respectively). In addition, the complexes showed cytotoxicity on human promyelocytic leukemia HL-60 cells with IC(50) values of the same order of magnitude as cisplatin. The interaction of the complexes with DNA was demonstrated by different techniques, suggesting that this biomolecule could be a potential target either in the parasites or in tumor cells.

Design and characterization of Cu(II) complexes from 2-benzoylpyridine benzhydrazone: crystallographic evidence for coordination versatility

The syntheses and characterization of six copper(II) complexes of 2-benzoylpyridine benzhydrazone in the form of [Cu(BPB)(2)], [Cu(BPB)Cl].H(2)O, [Cu(BPB)Br], [Cu(2)(BPB)(2)](ClO(4))(2).4H(2)O, [Cu(BPB)N(3)].H(2)O, and [Cu(BPB)NCS].H(2)O.CH(3)OH are reported. The analytical methods used for the characterization of complexes include partial elemental analyses, IR, electronic and EPR spectra, conductivity measurements, magnetic susceptibility measurements and single crystal X-ray diffraction. From the crystal structure, it is clear that the hydrazone adopts the E conformation about the azo bond to attach to the metal through the N(py)-N(azo)-O chelating system. In the EPR spectra of complexes in DMF at 77K four hyperfine quartets in the parallel region could be resolved and a half field signal is observed at 1500 G for complex [Cu(2)(BPB)(2)](ClO(4))(2).4H(2)O in polycrystalline state at 298 K which gives evidence for its binuclear nature indicating a weak interaction between the two Cu(II) ions.