Theoretical Investigation by DFT and Molecular Docking of Synthesized Oxidovanadium(IV)-Based Imidazole Drug Complexes as Promising Anticancer Agents.

Vanadium compounds have been set in various fields as anticancer, anti-diabetic, anti-parasitic, anti-viral, and anti-bacterial agents. This study reports the synthesis and structural characterization of oxidovanadium(IV)-based imidazole drug complexes by the elemental analyzer, molar conductance, magnetic moment, spectroscopic techniques, as well as thermal analysis. The obtained geometries were studied theoretically using density functional theory (DFT) under the B3LYP level. The DNA-binding nature of the ligands and their synthesized complexes has been studied by the electronic absorption titrations method. The biological studies were carried with in-vivo assays and the molecular docking method. The EPR spectra asserted the geometry around the vanadium center to be a square pyramid for metal complexes. The geometries have been confirmed using DFT under the B3LYP level. Moreover, the quantum parameters proposed promising bioactivity of the oxidovanadium(IV) complexes. The results of the DNA-binding revealed that the investigated complexes bind to DNA via non-covalent mode, and the intrinsic binding constant (Kb) value for the [VO(SO4)(MNZ)2] H2O complex was promising, which was 2.0 × 106 M-1. Additionally, the cytotoxic activity of the synthesized complexes exhibited good inhibition toward both hepatocellular carcinoma (HepG-2) and human breast cancer (HCF-7) cell lines. The results of molecular docking displayed good correlations with experimental cytotoxicity findings. Therefore, these findings suggest that our synthesized complexes can be introduced as effective anticancer agents.

QSAR Modeling, Molecular Docking and Cytotoxic Evaluation for Novel Oxidovanadium(IV) Complexes as Colon Anticancer Agents.

Four new drug-based oxidovanadium (IV) complexes were synthesized and characterized by various spectral techniques, including molar conductance, magnetic measurements, and thermogravimetric analysis. Moreover, optimal structures geometry for all syntheses was obtained by the Gaussian09 program via the DFT/B3LYP method and showed that all of the metal complexes adopted a square-pyramidal structure. The essential parameters, electrophilicity (ω) value and expression for the maximum charge that an electrophile molecule may accept (ΔNmax) showed the practical biological potency of [VO(CTZ)2] 2H2O. The complexes were also evaluated for their propensity to bind to DNA through UV-vis absorption titration. The result revealed a high binding ability of the [VO(CTZ)2] 2H2O complex with Kb = 1.40 × 106 M-1. Furthermore, molecular docking was carried out to study the behavior of the VO (II) complexes towards colon cancer cell (3IG7) protein. A quantitative structure-activity relationship (QSAR) study was also implemented for the newly synthesized compounds. The results of validation indicate that the generated QSAR model possessed a high predictive power (R2 = 0.97). Within the investigated series, the [VO(CTZ)2] 2H2O complex showed the greatest potential the most selective compound comparing to the stander chemotherapy drug.

Antioxidant, anticancer activities and mechanistic studies of the flavone glycoside diosmin and its oxidovanadium(IV) complex. Interactions with bovine serum albumin.

The natural antioxidant flavonoid diosmin, found in citric fruits, showed low antioxidant properties among other flavonoids due to its structural characteristics and low cytotoxicity against lung (A549) and breast (T47D, SKBR3 and MDAMB231) cancer cell lines. The anticancer behavior has been improved by the metal complex generated with the flavonoid and the oxidovanadium(IV) ion. This new complex, [VO(dios)(OH)3]Na5·6H2O (VOdios), has been synthesized and characterized both in solid and solution states. The interaction of the metal ion through the sugar moiety of diosmin precluded the improvement of the antioxidant effects. However, the cell-killing effects tested in human lung A549 and breast T47D, SKBR3 and MDAMB231 cancer cell lines, were enhanced by complexation. The anti-proliferative effects on the human lung cancer cell line were accompanied by cellular ROS generation and an increase in cytoplasm condensation. The breast cancer cell lines did not produce caspase3/7 activation, mitochondrial potential reduction and ROS generation. Therefore, a non-apoptotic form of cell death in a caspase- and oxidative stress-independent manner has been proposed. The protein binding ability has been monitored by the quenching of tryptophan emission in the presence of the compounds using bovine serum albumin (BSA) as a model protein. Both compounds could be distributed and transported in vivo and the complex displayed stronger binding affinity and higher contributions to the hydrogen bond and van der Waals forces.

Solution chemical properties and anticancer potential of 8-hydroxyquinoline hydrazones and their oxidovanadium(IV) complexes.

We report the synthesis and characterization of a family of benzohydrazones (Ln, n = 1-6) derived from 2-carbaldehyde-8-hydroxyquinoline and benzylhydrazides containing different substituents in the para position. Their oxidovanadium(IV) complexes were prepared and compounds with 1:1 and 1:2 metal-to-ligand stoichiometry were obtained. All compounds were characterized by elemental analyses and mass spectrometry as well as FTIR, UV-visible absorption, NMR (ligand precursors) and EPR (complexes) spectroscopies, and by DFT computational methods. Proton dissociation constants, lipophilicity and solubility in aqueous media were determined for all ligand precursors. Complex formation with V(IV)O was evaluated by spectrophotometry for L4 (Me-substituted) and L6 (OH-substituted) and formation constants for mono [VO(HL)]+, [VO(L)] and bis [VO(HL)2], [VO(HL)(L)]-, [VO(L)2]2- complexes were determined. EPR spectroscopy indicates the formation of [VO(HL)]+ and [VO(HL)2], with this latter being the major species at the physiological pH. Noteworthy, the EPR data suggest a different behaviour for L4 and L6, which confirm the results obtained in the solid state. The antiproliferative activity of all compounds was evaluated in malignant melanoma (A-375) and lung (A-549) cancer cells. All complexes show much higher activity on A-375 (IC50 < 6.3 µM) than in A-549 cells (IC50 > 20 µM). Complex 3 (F-substituted) shows the lowest IC50 on both cell lines and lower than cisplatin (in A-375). Studies identified this compound as the one showing the highest increase in Annexin-V staining, caspase activity and induction of double stranded breaks, corroborating the cytotoxicity results. The mechanism of action of the complexes involves reactive oxygen species (ROS) induced DNA damage, and cell death by apoptosis.

Evaluation of cellular uptake, cytotoxicity and cellular ultrastructural effects of heteroleptic oxidovanadium(IV) complexes of salicylaldimines and polypyridyl ligands.

Searching for prospective vanadium-based drugs for cancer treatment, a new series of structurally related [VIVO(L-2H)(NN)] compounds (1-8) was developed. They include a double deprotonated salicylaldimine Schiff base ligand (L-2H) and different NN-polypyridyl co-ligands having DNA intercalating capacity. Compounds were characterized in solid state and in solution. EPR spectroscopy suggests that the NN ligands act as bidentate and bind through both nitrogen donor atoms in an axial-equatorial mode. The cytotoxicity was evaluated in human tumoral cells (ovarian A2780, breast MCF7, prostate PC3). The cytotoxic activity was dependent on type of cell and incubation time. At 24h PC3 cells presented low sensitivity, but at 72h all complexes showed high cytotoxic activity in all cells. Human kidney HEK293 and ovarian cisplatin resistant A2780cisR cells were also included to evaluate selectivity towards cancer cells and potency to overcome cisplatin resistance, respectively. Most complexes showed no detectable interaction with plasmid DNA, except 2 and 7 which depicted low ability to induce single strand breaks in supercoiled DNA. Based on the overall cytotoxic profile, complexes with 2,2´-bipyridine and 1,10-phenanthroline ligands (1 and 2) were selected for further studies, which consisted on cellular distribution and ultrastructural analyses. In the A2780 cells both depicted different distribution profiles; the former accumulates mostly at the membrane and the latter in the cytoskeleton. Morphology of treated cells showed nuclear atypia and membrane alterations, more severe for 1. Complexes induce different cell death pathways, predominantly necrosis for 1 and apoptosis for 2. Complexes alternative mode of cell death motivates the possibility for further developments.

Bovine serum albumin binding, antioxidant and anticancer properties of an oxidovanadium(IV) complex with luteolin.

Chemotherapy using metal coordination compounds for cancer treatment is the work of the ongoing research. Continuing our research on the improvement of the anticancer activity of natural flavonoids by metal complexation, a coordination compound of the natural antioxidant flavone luteolin (lut) and the oxidovanadium(IV) cation has been synthesized and characterized. Using different physicochemical measurements some structural aspects of [VO(lut)(H2O)2]Na·3H2O (VOlut) were determined. The metal coordinated to two cis-deprotonated oxygen atoms (ArO(-)) of the ligand and two H2O molecules. Magnetic measurements in solid state indicated the presence of an effective exchange pathway between adjacent vanadium ions. VOlut improved the antioxidant capacity of luteolin only against hydroxyl radical. The antitumoral effects were evaluated on MDAMB231 breast cancer and A549 lung cancer cell lines. VOlut exhibited higher viability inhibition (IC50=17 µM) than the ligand on MDAMB231 cells but they have the same behavior on A549 cells (ca. IC50=60 µM). At least oxidative stress processes were active during cancer cell-killing. When metals chelated through the carbonyl group and one adjacent OH group of the flavonoid an effective improvement of the biological properties has been observed. In VOlut the different coordination may be the cause of the small improvement of some of the tested properties of the flavonoid. Luteolin and VOlut could be distributed and transported in vivo. Luteolin interacted in the microenvironment of the tryptophan group of the serum binding protein, BSA, by means of electrostatic forces and its complex bind the protein by H bonding and van der Waals interactions.

Insights into the mechanisms underlying the antitumor activity of an oxidovanadium(IV) compound with the antioxidant naringenin. Albumin binding studies.

Naringenin, a natural antioxidant present in grapefruit, oranges and the skin of tomatoes showed low antioxidant properties among other flavonoids due to its structural characteristics. Since many flavonoids were shown to have cell-killing and antioxidant activities, naringenin was investigated herein. In parallel with its antioxidant activities the flavonoid showed very low cytotoxicity at concentrations up to 100 µM against lung (A549) and breast (SKBr3 and MDAMB231) cancer cell lines. Furthermore, a newly-synthesized and characterized complex of naringenin and oxidovanadium(IV) ([V(IV)O(nar)2] · 2H2O, VOnar, with weak ferromagnetic coupling) was also studied. As a result, VOnar acted as a better compound on cell-killing and antioxidant activities (in vitro) than naringenin. The anti-proliferative effect of VOnar was accompanied by reactive oxygen species (ROS) generation, cell membrane and DNA damages, cell cycle arrest, caspase 3/7 activation and mitochondrial potential reduction. The higher parameters observed for the MDAMB231 cell line have been related to its low glutathione (GSH) content. The assays of the interaction of bovine serum albumin (BSA) with the complex showed the affinity of protein toward it and that there is only one binding site on the BSA molecule. However, metal complexation decreased the binding affinity to BSA of naringenin probably due to a steric hindrance of the complex.

pH-metric chemical speciation modeling and studies of in vitro antidiabetic effects of bis[(imidazolyl)carboxylato]oxidovanadium(IV) complexes.

A range of bidentate N,O-donor ligands of the imidazolyl-carboxylate moiety, which partially mimic naturally occurring bioligands, were prepared and reacted with the oxidovanadium(IV) ion to form the corresponding bis-coordinated oxidovanadium(IV) complexes. The aqueous pH-metric chemical speciation was investigated using glass electrode potentiometry, which allowed for the determination of protonation and stability constants of the ligands and complexes, respectively. The species distribution diagrams generated from this information gave evidence that the bis[(imidazolyl)carboxylato]oxovanadium(IV) complexes possess a broad pH-metric stability. The complexes improved glucose uptake in cell cultures using 3T3-L1 adipocytes, C2C12 muscle cells and Chang liver cells. The PTP inhibition studies indicated that the mechanism underlying insulin-stimulated glucose uptake was possibly via the protein tyrosine phosphorylation through the inhibition of the protein tyrosine phosphatase 1B (PTP 1B). The vanadium compounds also demonstrated the inhibition of D-dimer formation, suggesting that these compounds could potentially relieve a hypercoagulative state in diabetic patients.

Expanding the family of heteroleptic oxidovanadium(IV) compounds with salicylaldehyde semicarbazones and polypyridyl ligands showing anti-Trypanosoma cruzi activity.

Searching for prospective vanadium-based drugs for the treatment of Chagas disease, a new series of heteroleptic [V(IV)O(L-2H)(NN)] compounds was developed by including the lipophilic 3,4,7,8-tetramethyl-1,10-phenanthroline (tmp) NN ligand and seven tridentate salicylaldehyde semicarbazone derivatives (L1-L7). The compounds were characterized in the solid state and in solution. EPR spectroscopy suggests that the NN ligand is bidentate bound through both nitrogen donor atoms in an axial-equatorial mode. The EPR and (51)V-NMR spectra of aerated solutions at room temperature indicate that the compounds are stable to hydrolysis and that no significant oxidation of V(IV) to V(V) takes place at least in 24h. The complexes are more active in vitro against Trypanosoma cruzi, the parasite responsible for Chagas disease, than the reference drug Nifurtimox and most of them are more active than previously reported [V(IV)O(L-2H)(NN)] complexes of other NN co-ligands. Selectivity towards the parasite was analyzed using J-774 murine macrophages as mammalian cell model. Due to both, high activity and high selectivity, L2, L4, L5 and L7 complexes could be considered new hits for further drug development. Lipophilicity probably plays a relevant role in the bioactivity of the new compounds. The [V(IV)O(L-2H)(NN)] compounds were designed aiming DNA as potential molecular target. Therefore, the novel L1-L7 tmp complexes were screened by computational modeling, comparing their DNA-binding features with those of previously reported [V(IV)O(L-2H)(NN)] compounds with different NN co-ligands. Whereas all the complexes interact well with DNA, with binding modes and strength tuned in different extents by the NN and semicarbazone co-ligands, molecular docking suggests that the observed anti-T. cruzi activity cannot be explained upon DNA intercalation as the sole mechanism of action.

Vanadium and cancer treatment: antitumoral mechanisms of three oxidovanadium(IV) complexes on a human osteosarcoma cell line.

We report herein the antitumor actions of three oxidovanadium(IV) complexes on MG-63 human osteosarcoma cell line. The three complexes: VO(oda), VO(oda)bipy and VO(oda)phen (oda=oxodiacetate), caused a concentration dependent inhibition of cell viability. The antiproliferative action of VO(oda)phen could be observed in the whole range of concentrations (at 2.5 µM), while VO(oda)bipy and VO(oda) showed a decrease of cell viability only at higher concentrations (at 50 and 75 µM, respectively) (p<0.01). Moreover, VO(oda)phen caused a decrease of lysosomal and mitochondrial activities at 2.5 µM, while VO(oda) and VO(oda)bipy affected neutral red uptake and mitochondrial metabolism at 50 µM (p<0.01). On the other hand, no DNA damage studied by the Comet assay could be observed in MG-63 cells treated with VO(oda) at 2.5-10 µM. Nevertheless, VO(oda)phen and VO(oda)bipy induced DNA damage at 2.5 and 10 µM, respectively (p<0.01). The generation of reactive oxygen species increased at 10 µM of VO(oda)phen and only at 100 µM of VO(oda) and VO(oda)bipy (p<0.01). Besides, VO(oda)phen and VO(oda)bipy triggered apoptosis as determined by externalization of the phosphatidylserine. The determination of DNA cleavage by agarose gel electrophoresis showed that the ability of VO(oda)(bipy) is similar to that of VO(oda), while VO(oda)(phen) showed the highest nuclease activity in this series. Overall, our results showed a good relationship between the bioactivity of the complexes and their structures since VO(oda)phen presented the most potent antitumor action in human osteosarcoma cells followed by VO(oda)bipy and then by VO(oda) according to the number of intercalating heterocyclic moieties.

Oxidovanadium(IV) and dioxidovanadium(V) complexes of tridentate salicylaldehyde semicarbazones: searching for prospective antitrypanosomal agents.

As a contribution to the identification of the relevant species for biological activity and the understanding of structure-activity relationships of [V(IV)O(L-2H)(NN)] antitrypanosomal complexes (NN is a bidentate polypyridyl DNA intercalator; L is a tridentate salicylaldehyde semicarbazone derivative), new [V(V)O2(L-2H)] complexes and [V(IV)O(L-2H)(NN)] complexes including bipy or dppz (dipyrido[3,2-a: 2',3'-c]phenazine) co-ligands are prepared and characterized in the solid state and in solution. Their activity is evaluated on Trypanosoma cruzi. The lipophilicity, as structural descriptor related to bioactivity, of the whole [V(IV)O(L-2H)(NN)] series is determined. Furthermore, the antiproliferative effect of those new compounds showing activity against T. cruzi is evaluated on the genetically related parasite T. brucei with the aim to develop broad spectrum agents. The new [V(IV)O(L-2H)(dppz)] complexes are about ten to fifteen times more toxic to T. cruzi than the bipy analogues and show quite good in vitro activity on T. brucei brucei. They are shown to interact with DNA, suggesting that this biomolecule may be the parasite target. The stability of the V(IV)O-complexes in solution is accessed by several techniques. Globally the data suggest that the relevant species for biological activity are the [V(IV)O(L-2H)(NN)] compounds, their order of activity being dependent on the NN nature, but not much on the substitution on the salicylaldehyde semicarbazone moiety. A parabolic relationship between biological response and lipophilicity (determined as RM=log [(1/Rf)-1] by a TLC method) is obtained. From this correlation an optimum RM value, close to 1.44, was found, which may be used as design guide for future development of antitrypanosomal compounds.