Polynuclear diorganotin(IV) complexes with arylhydroxamates: Syntheses, structures and in vitro cytotoxic activities

Synthesis and in vitro cytotoxicity study of three di-organotin(IV) Schiff base di-acylhydrazone complexes

Three di-organotin(IV) complexes have been synthesized by the reaction of Schiff base di-acylhydrazone ligands bis(5-chlorosalicylaldehyde) adipoylhydrazone and R2SnCl2 [R = Me (1), Ph (2), n-Bu (3)]. Structures of all complexes were characterized by 1H, 13C, 119Sn NMR, elemental analysis, IR and mass spectrometry. Experimental results showed that the symmetric diacylhydrazone ligands coordinate the tin atom in a hexadentate form, where the tin atom shows a penta-coordination, in a distorted triangular bipyramid geometry. Using MTT method, in vitro cytotoxicity of three complexes was determined against three cancer cell lines (A549, HeLa, HepG-2). Studies reveal that complex 3 showed the strongest cytotoxic activity among the three complexes, which may be correlated with the generation of intracellular reactive oxygen species. Uptake of complex 3 into cells and promotion of reactive oxygen species were visualized by confocal fluorescence imaging.

Density functional theory studies on molecular geometry, spectroscopy, HOMO-LUMO and reactivity descriptors of titanium(IV) and oxidozirconium(IV) complexes of phenylacetohydroxamic acid

The molecular geometry of new titanium(IV) and oxidozirconium(IV) phenylacetohydroxamate complexes [TiCl₂ (L1)₂ ] (I) and [ZrO(L1)₂ ] (II) (where L1 = Potassium phenylacetohydroxamate = C₆ H₅ CH₂ CONHOK) computed by B3LYP/6-311++G(d,p) method has shown these to be distorted octahedral and square pyramidal, respectively. A comparison of computed characteristic bond lengths (CO, CN, and NO) of complexes with that of free ligand has shown chelation through carbonyl and hydroxamic oxygen atoms (O, O coordination). The TiO/ZrO bond lengths in complexes are suggestive of weak coordination through (carbonyl CO) and strong covalent (hydroxamic NO) bonding of the ligand. The magnitude of ClTiCl bond angle involving two chloride atoms is suggestive of cis-conformation at titanium metal in (I). The thermodynamic parameters Gibbs free energy, enthalpy, entropy, nuclear internal energy, constant volume heat capacity, and internal energy of ligand and complexes have been computed. From the energies of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), the global reactivity descriptors such as ionization potential (IP), electron affinity (EA), chemical potential (μ), hardness (η), softness (S), electronegativity (χ), electrophilicity index (ω), and dipole moment have been calculated. The computed vibrational frequencies, ¹ H and ¹³ C NMR spectra have substantiated the molecular structure of complexes. The thermal behavior of complexes has been studied by thermogravimetric techniques (TGA, DTG, and DTA) in N₂ atmosphere has shown complexes are thermally stable.

Organotin compound DBDCT induces CYP3A suppression through NF-κB-mediated repression of PXR activity

Organotin anticancer agent di-n-butyl-di-(4-chlorobenzohydroxamato)tin(iv) (DBDCT) exerted an inhibitory effect on its major metabolic enzyme cytochrome CYP3A. But whether hepatic drug-metabolizing enzymes and their regulatory nuclear receptors including pregnane PXR and constitutive androstane CAR binding with retinoid receptor RXR as a heterodimer are involved in the DBDCT-mediated regulation of CYP3A remains unclear. This study was undertaken to determine the mechanisms responsible for the effects of DBDCT on CYP3A suppression, focusing on the PXR-mediated and NF-κB pathways. The results indicated DBDCT suppressed CYP3A expression by inhibiting CAR expression. But what's interesting is, both protein and mRNA of PXR increased with increasing DBDCT. A further exploration, dual luciferase reporter gene analysis, clarified that DBDCT induced CYP3A expression elevation via the PXR-mediated pathway and this induction was countered by activation of NF-κB, which played a pivotal role in suppression of CYP3A through disrupting the association of the PXR-RXRα complex with DNA sequences by EMSA. PXR-mediated CYP3A expression was similarly demonstrated by RNAi. As expected, expression of CYP3A and its mRNA levels were reduced by DBDCT only in NF-κB(+/+) but not in NF-κB(-/-) cells. The inductive effect of DBDCT on CYP3A4 mRNA was enhanced in PXR shRNA-transfected cells but weakened in the ip65 group, which showed both PXR up-regulated CYP3A expression and NF-κB p65 activation directly contributed to CYP3A inhibition. In conclusion, activated NF-κB by DBDCT interacts directly with the DNA-binding domain of PXR, and disrupts the binding between the PXR-RXR dimer, thereby affecting the regulatory process for CYP3A transcription and, therefore, leading to a decrease of the expression of the PXR-regulated CYP3A.

Distinctive coordination behavior of a pyrazole imine-oxime compound towards Co(II) and Ni(II)

The polytopic Schiff base 5-methyl-1H-pyrazole-3-carboxylic acid 2-(hydroxyimino-1-methyl-propylidene)-hydrazide (H₂L)was synthesized by the condensation of 5-methyl pyrazole-3-carbohydrazide and 3-(hydroxyimino)butan-2-one and its coordination ability was tested against cobalt (II) and nickel (II) nitrates. The ligand exhibited two different binding modes to form a unique binuclear triply bridged Co(III) cationic complex [Co₂(1κN²:2κN²-L) (1κN³:2κO¹-HL)₂](NO₃)₂ (1). With the Ni(II) precursor, H₂L was hydrolyzed to N′,N˝-butane-2,3-diylidenebis (5-methyl-1H-pyrazole-3-carbohydrazide) (H₂L¹) which bound the metal cation in a tetradentate N₃O₁ fashion leading to the neutral square planar complex [Ni(κN³O¹-L¹)]·MeOH (2·MeOH). Complexes 1 and 2 were characterized by IR, NMR, UV-Vis and single crystal X-ray crystallography. The probable mechanism for the Ni(II) mediated transformation of H₂L into H₂L¹ has been investigated by ESI-MS.

Anti-proliferative and antitumor activity of organotin(IV) compounds. An overview of the last decade and future perspectives

Organotins(IV) exhibit significant in vitro anti-proliferative activity, while the in vivo tests are encouraging. The recent reports on the anti-proliferative activity of organotin(IV) compounds are summarized in this review. The period covered by this work goes back to 2009 until late 2018, while the earlier ones, are included over the previous review of our group published by S.K. Hadjikakou, N. Hadjiliadis, in Coord Chem Rev, 253 (2009) 235-249. During the last decade (2009-2018), >300 organotin(IV) derivatives with oxygen-donor ligands, such as carboxylic acids, amino-acids, Non Steroidal Anti-inflammatory Drugs (NSAIDs), biological active derivatives or natural products, organotins(IV) with sulfur containing ligands such as thiones, thiosemicarbazones, dithiocarbamates, organotin(IV) compounds of oximes and organotins(IV) with amines or semicarbazones were screened for their anti-proliferative effect against various cancer cell lines and their results are included in numerous reports over this period. Although much work has been carried out on organotin(IV) derivatives with O-donor ligands, however significant fewer reports are found on organotins(IV) with oximes as ligands.

Carbohydrate-based heteronuclear complexes as topoisomerase Iα inhibitor: approach toward anticancer chemotherapeutics

Due to the critical role of cellular enzymes necessary for cell proliferation by deciphering topological hurdles in the process of DNA replication, topoisomerases have been one of the major targets in the anticancer drug development area. A need, therefore, arises for new metallodrugs that specifically recognizes DNA and inhibits the activity of topoisomerase enzymes, herein, we report the synthesis and characterization of new metal-based glycoconjugate entities containing heterobimetallic core Cu^II-Sn^IV (1) and Ni^II-Sn^IV (2) derived from N-glycoside ligand (L). The optimized structure of complex 1 and other significant vibrational modes have been explained using dispersion corrected B3LYP/DFT calculations. In vitro DNA binding profile of the L and both the complexes 1 and 2 were done by various biophysical studies. Complex 1 breaks pBR322 DNA via a hydrolytic means which was validated by T4 DNA enzymatic assay. To get a mechanistic insight of mode of action topoisomerase I (Topo I) inhibition assay was carried out. Also, we have taken the help of molecular modeling studies in accordance with experimental findings. In vitro cytotoxicity of the complex 1 was evaluated against a panel of cancer cells which exhibited remarkably good anticancer activity (GI₅₀ values <10 μg/ml). Moreover, intracellular localization of the complex 1 was visualized by confocal microscopy against HeLa cells.

Therapeutic properties of organotin complexes with reference to their structural and environmental features

Organotin complexes are being extensively studied and screened for their therapeutic potential. Although many recent advances and achievements in this field have been made, the exact mode of action of these complexes is yet to be unveiled. In the present review, an attempt has been made to correlate the therapeutic properties of organotin complexes with their structural features and the environment in which these interact with biological systems. The mechanism, various modes of interaction with biological systems, and physiological target sites of organotin complexes have been highlighted as well.

Unfolding biological properties of a versatile dicopper(II) precursor and its two mononuclear copper(II) derivatives

Synthesis, inter-conversions and biological study of the dichloro bridged dicopper(II) compound [CuLCl]₂ (1) and its two mononuclear derivatives [CuLCl(H₂O)]·H₂O (2) and [CuLCl(py)] (3) (HL=2-(2-pyridylmethyleneamino)benzenesulfonic acid) are described. The dimeric compound 1 collapses into monomers 2 and 3 in the presence of coordinating solvents, water and pyridine, respectively, and 1 is regenerated upon simple stirring of 2 or 3 in methanol. The reactions of 1 with neutral (present study) and charged (earlier studies) ligands result in monomeric and multimeric compounds, respectively, attesting that it is a versatile dicopper(II) precursor. The anticancer activity of these copper complexes (1-3) was screened against lung (A-549) and breast (MDA-MB-231) human cancer cell lines. The IC₅₀ (half maximal inhibitory concentration) value for one (3) of the compounds suggests preferential cytotoxicity against breast cancer MDA-MB-231 cell line. Furthermore, the IC₅₀ value obtained for complex 3 is found to be almost two-fold times cytotoxic than the standard drug cisplatin. In addition, the underlying possible mechanism of its apoptosis-inducing efficacy in MDA-MB-231 cells has been rationalized by using flow cytometry (FACS) and Hoechst 33342/propidium iodide (PI) fluorescence staining. The stimulation of apoptotic induction for complex 3 has further been affirmed by reactive oxygen species (ROS) generation and mitochondrial aggregations studies.

In vitro and in vivo biological characterization of the anti-proliferative potential of a cyclic trinuclear organotin(iv) complex

Identification of novel molecules that can selectively inhibit the growth of tumor cells, avoid causing side effects to patients and/or intrinsic or acquired resistance, usually associated with common chemotherapeutic agents, is of utmost importance. Organometallic compounds have gained importance in oncologic chemotherapy, such as organotin(iv) complexes. In this study, we assessed the anti-tumor activity of the cyclic trinuclear organotin(iv) complex with an aromatic oximehydroxamic acid group [nBu2Sn(L)]3(H2L = N,2-dihydroxy-5-[N-hydroxyethanimidoyl]benzamide) - MG85 - and provided further characterization of its biological targets. We have previously shown the high anti-proliferative activity of this complex against human colorectal and hepatocellular carcinoma cell lines and lower cytotoxicity in neonatal non-tumor fibroblasts. MG85 induces tumor cell apoptosis and down-regulation of proteins related to tubulin dynamics (TCTP and COF1). Further characterization included the: (i) evaluation of interference in the cell cycle progression, including the expression of critical genes; (ii) affinity to DNA and the corresponding mode of binding; (iii) genotoxic potential in cells with deficient DNA repair pathways; and (iv) in vivo tumor reduction efficiency using mouse colorectal carcinoma xenografts.

Sulfonated Schiff base Sn(IV) complexes as potential anticancer agents

Syntheses, crystal structures and biological activities of the diphenoxo-bridged diorgano dinuclear Sn(IV) compounds [Sn(Et)₂(HL)(H₂O)]₂ (1) and [Sn(n-Bu)₂(HL)(H₂O)]₂ (2) derived from the Schiff base 2-[(2,3-dihydroxyphenyl)methylideneamino]benzenesulfonic acid trihydrate (H₃L·3H₂O) are described. The monoprotonated form (HL^2-) of the Schiff base behaves as O,O'-bidentate ligand, chelating the metal by the two phenoxo oxygen atoms. The hexacoordinated metal centres in 1 and 2 are bridged by a phenoxo oxygen and the remaining coordination positions are fulfilled by the other phenoxo oxygen, two organic groups (ethyl for 1 and n-butyl for 2) and a water molecule. A two dimensional zigzag sheet in 1 and three dimensional polymeric networks in H₃L·3H₂O and 2 are stabilized by a number of non-covalent, H-bonding and π⋯π stacking interactions. The DNA binding activities of these complexes have been studied by UV-vis and fluorescence spectroscopies. Their antiproliferative efficacies have been evaluated on A-549, HeLa and MDA-MB-231 cancer cell lines by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. IC₅₀ values (1.35±0.23, 2.43±0.54 and 1.74±0.04μM for 2) are indicative of a substantial cytotoxicity of 2, mainly towards the A-549 lung cancer cell line. The greater antiproliferative efficacy of 2has further been studied by fluorescence activated cell sorting (FACS) and nuclear morphology by Hoechst/propidium iodide (PI) double staining method. The possible mode of the apoptotic pathway for 2has been substantiated by the reactive oxygen species (ROS) generation studies.

A sulfonated Schiff base dimethyltin(iv) coordination polymer: synthesis, characterization and application as a catalyst for ultrasound- or microwave-assisted Baeyer–Villiger oxidation under solvent-free conditions

The sulfonated Schiff base dimethyltin(iv) coordination polymer is an efficient heterogeneous catalyst for the peroxidative Baeyer–Villiger oxidation of ketones, under ultrasound or microwave irradiation and solvent- and additive-free conditions.

Dimeric diorganotin(iv) complexes with arylhydrazones of β-diketones: synthesis, structures, cytotoxicity and apoptosis properties

The apoptosis induction of the new dimeric diorganotin(iv) complexes correlates with the cytotoxicity. The mechanism of KB cell death might occur mainly by means of early apoptosis.

Organotin(IV) complexes derived from Schiff base N'-[(1E)-(2-hydroxy-3-methoxyphenyl)methylidene]pyridine-4-carbohydrazone: synthesis, in vitro cytotoxicities and DNA/BSA interaction

Five organotin(IV) compounds were synthesized from N'-[(1E)-(2-hydroxy-3-methoxyphenyl)methylidene]pyridine-4-carbohydrazone and the corresponding dialkyltin(IV) or trialkyltin(IV) precursor. Solid state structures were determined by IR, elemental analysis, NMR spectroscopy, and for 1, 2, 4 and 5 single crystal X-ray diffraction analysis. Compounds 1, 2 and 4 are monomers with the tin atoms five-coordinated in distorted trigonal bipyramid, of which the deprotonated Schiff base ligand chelate to tin center in the enolic tridentate mode. Differently, in compound 5, the enolization does not occur for the Schiff base ligand, and only the pyridinyl N atom and the deprotonated phenol hydroxyl oxygen atom participate in the coordination. Fascinatingly, six trimethyltin(IV) coordination units are linked by the Sn⋯N weak interaction atoms and form a 72-membered crown-like macrocycle. Preliminary in vitro cytotoxicity studies on five human tumor cells lines (HL-60, A549, HT-29, HCT-116 and Caco-2) by MTT assay reveal that di-n-butyltin(IV) complex 2 and diphenyltin(IV) complex 4 triggered significant antiproliferative effects in cultured tumor cells, and their cytotoxic activity correlates with intracellular organotin(IV) concentration. The interaction of the complexes with calf thymus DNA (CT-DNA) has been explored by absorption and emission titration methods, which revealed that complexes 2 and 4 interact with CT-DNA through groove-binding and partial intercalation of the extended planar ligand with the DNA base stack. Further, the albumin interactions of complexes 2 and 4 were investigated using fluorescence quenching spectra and synchronous fluorescence spectra. Studies reveal that di-n-butyltin(IV) complex 2 with higher cytotoxicity show stronger DNA/BSA interaction than diphenyltin(IV) complex 4.

Novel mixed ligand di-n-butyltin(IV) complexes derived from acylpyrazolones and fluorinated benzoic acids: synthesis, characterization, cytotoxicity and the induction of apoptosis in Hela cancer cells

Twenty one novel mixed ligand di-n-butyltin(IV) complexes [(n)Bu2SnAL] (A = substituted 4-acyl-5-pyrazolone, and L = fluorinated benzoic acid) were prepared by condensation of di-n-butyltin(IV) oxide with HL and HA in 1:1:1 molar ratio in refluxing methanol. All of the complexes were characterized by elemental analyses, IR, NMR ((1)H, (13)C, (119)Sn) and in four cases by X-ray diffraction. Cytotoxicity of the compounds was studied against two human cancer cell lines (KB and Hela) by means of the MTT assay compared to cisplatin, featuring IC₅₀ values in the low micromolar range. Hela cancer cell apoptosis-induced by 2 was examined by flow cytometry analysis, and preliminary results showed that 2 at concentrations of more than 1.0 μM can induce apoptosis.

Diorganotin(IV) derivatives of substituted N-hydroxybenzamides with selective cytotoxicity in vitro and potent antitumor activity in vivo

Four diorganotin(IV) derivatives, dibutylbis[4-chloro-N-(hydroxy-<κ>O)benzamidato-<κ>O]tin(IV) (DBDCT), dibutylbis[2,6-difluoro-N-(hydroxy-<κ>O)benzamidato-<κ>O]tin(IV) (DBDFT), bis[2,4-difluoro-N-(hydroxy-<κ>O)benzamidato-<κ>O]diphenyltin(IV) (DPDFT), and bis[2,4-dichloro-N-(hydroxy-<κ>O)benzamidato-<κ>O]diphenyltin(IV) (DPDCT), were compared for their antitumor activity in vitro and in vivo along with their cytotoxic selectivity against human normal cells and cancer cells. The in vitro cytotoxic activities against seven human cancer cell lines including Hep G2, SHSY5Y, HEC-1-B, EC, T24, HeLa and A549 along with human liver HL-7702, a human normal hepatocytes cell, were observed by the MTT assay. The cytotoxic selectivity of the four compounds was compared by using HL-7702 and Hep G2. The in vivo antitumor tests towards the sarcoma carcinoma S180 and hepatocellular carcinoma H22 on mice were carried out via injection intraperitoneally with cisplatin as the positive contrast drug. The results showed that, among the four compounds, DBDCT displayed the strongest cytotoxicity against the seven cancer cell lines. DPDCT had the highest antitumor activity in vivo. However, both of them had no cytotoxic selectivity against the human hepatocellular carcinoma HepG2 cells and normal liver HL-7702 cells. DPDFT had the most significant cytotoxic selectivity against HepG2 and displayed significantly antitumor activity in vitro and in vivo. In conclusion, DPDFT could act as a promising lead compound for the further structure optimization owing to its relatively low toxicity to human normal cell and potent antitumor activity against cancer cells.

Kinetics and Mechanism of Nucleophilic Substitution in SnR2Cl2 · 2DMSO by Chloride Ions in Micellar Microenvironment

The kinetics of nucleophilic substitution of dimethylsulfoxide by chloride ion in bis-dimethyl sulfoxide dimethyltin(IV) dichloride and bis-dimethyl sulfoxide diphenyltin(IV) dichloride in micellar microenvironment (1.0 × 10–2 M SDS in aqueous solution of ethanol (1:1, v/v) has been studied conductometrically. The reactions have been carried out at 25°C. Substitution follows first order path with respect to chloride ion concentration. A millimolar solution of the complexes in ethanolic solution of 1.0 × 10–2 M SDS shows an increase in conductance with time due to solvation of the molecule. Sn(CH3)2Cl2 · 2 DMSO shows high conductance as compared to Sn(C6H5)2Cl2 · 2 DMSO. In the presence of the nucleophilic reagents, C6H5COCl and CH3COCl there is a greater enhancement in conductance due to substitution of DMSO by chloride ion. The data of rate constant for solvation (KS) and for nucleophilic substitution (K1 and K2) have been calculated. It was found that the solvation is a slower process compared to the substitution by chloride ions i.e., K1, K2 > Ks. A possible mechanism has been suggested.

Inhibition of cytochrome P450 3A in rat liver by the Diorganotin (IV) compound di-n-Butyl-di-(4-chlorobenzo-hydroxamato)tin (IV) and Its Probable Mechanism

The specific aims of this study were to evaluate the inhibition effect on CYP3A of di-n-butyl-di-(4-chlorobenzohydroxamato)tin (IV) (DBDCT), a tin-based complex with high antitumor activity, and the probable mechanism(s) of this action. Adult male SD rats were treated separately with natural saline (NS), lipopolysaccharide (LPS, 5 mg/kg), DBDCT (1.25, 2.5 and 5.0 mg/kg) intraperitoneally for 2 days after induction of CYP3A with dexamethasone (DEX, 100 mg/kg) for 4 days. Western blot analysis and fluorescent quantitation PCR (FQ-PCR) were conducted to determine the changes in expression of CYP3A, PXR, CAR and RXR. The biological accumulation of DBDCT and total Sn were determined by high-performance liquid chromatography (HPLC) and atomic fluorescence spectrometry (AFS). CYP450 content and CYP3A activities were significantly inhibited (p < 0.05) in DBDCT-treated rats compared with the control group, as was the expression of CYP3A (p < 0.05) at both protein and mRNA levels. In DBDCT-treated groups, the expression of PXR protein and mRNA increased, while the expression of CAR decreased. The biological accumulation of DBDCT and Sn in rat livers treated with DBDCT was high. The accumulation of DBDCT and Sn due to the inhibition of CYP3A may be involved in the mechanism of toxicity of DBDCT in rat liver.