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

Synthesis and Characterization of Zn(II) Complex of 4-chloro-2-(((2-phenoxyphenyl)imino)methyl)phenol and its Biological Efficacies: DNA Interaction, ADMET, DFT and Molecular Docking Study

Condensing 2-phenoxyaniline with 5-chlorosalicyldehyde under reflux conditions, a 4-chloro-2-(((2-phenoxyphenyl)imino)methyl)phenol Schiff base has been Synthesized. A zinc complex was synthesized by combining the ligand in a 1:1 molar ratio with zinc sulphateheptahydrate. Mass spectroscopy, NMR, infrared, and elemental analysis were used to characterize the ligand and zinc complex. By measuring the molar conductance, the non-electrolytic character of the complex was confirmed. The zinc ion is coordinated in a pentadentate manner, according to an IR and NMR investigation. Viscosity measurements, absorption and fluorescence spectroscopy were utilized to examine the complex's interaction with CT (calf thymus) DNA. Furthermore, the ligand and complex's ADMET characteristics were ascertained through the use of ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) study. Calculation of the different electronic parameters of the optimized structure through Density Functional Theory (DFT) indicated the stability of the Zn(II) complex. Molecular docking study reflected the future opportunity for the consideration of Zn(II) complex to fight against Alzheimer and Glaucoma diseases.

Density Functional Theory-Guided Photo-Triggered Anticancer Activity of Curcumin-Based Zinc(II) Complexes

Photodynamic therapy (PDT) has evolved as a new therapeutic modality for cancer treatment with fewer side effects and drug resistance. Curcumin exhibits PDT activity, but its low bioavailability restricts its clinical application. Here, the bioavailability of curcumin was increased by its complex formation with the Zn(II) center. For a structure-activity relationship study, Zn(II)-based complexes (1-3) comprising N^N-based ligands (2,2'-bipyridine in 1 and 2 or 1,10-phenanthroline in 3) and O^O-based ligands (acetylacetone in 1, monoanionic curcumin in 2 and 3) were synthesized and thoroughly characterized. The X-ray structure of the control complex, 1, indicated a square pyramidal shape of the molecules. Photophysical and TD-DFT studies indicated the potential of 2 and 3 as good visible light type-II photosensitizers for PDT. Guided by the TD-DFT studies, the low-energy visible light-triggered singlet oxygen (1O2) generation efficacy of 2 and 3 was explored in solution and in cancer cells. As predicted by the TD-DFT calculations, these complexes produced 1O2 efficiently in the cytosol of MCF-7 cancer cells and ultimately displayed excellent apoptotic anticancer activity in the presence of light. Moreover, the molecular docking investigation showed that complexes 2 and 3 have very good binding affinities with caspase-9 and p-53 proteins and could activate them for cellular apoptosis. Further molecular dynamics simulations confirmed the stability of 3 in the caspase-9 protein binding site.

Design and synthesis of new adamantyl derivatives as promising antiproliferative agents

A series of adamantyl carboxamide derivatives containing sulfonate or sulfonamide moiety were designed as multitargeted inhibitors of ectonucleotide pyrophosphatases/phosphodiesterases (NPPs) and carbonic anhydrases (CAs). The target compounds were investigated for their antiproliferative activity against NCI-60 cancer cell lines panel. Three main series composed of 3- and 4-aminophenol, 4-aminoaniline, and 5-hydroxyindole scaffolds were designed based on a lead compound (A). Compounds 1e (benzenesulfonyl) and 1i (4-fluorobenzenesulfonyl) of 4-aminophenol backbone exhibited the most promising antiproliferative activity. Both compounds exhibited a broad-spectrum and potent inhibition against all the nine tested cancer subtypes. Both compounds showed nanomolar IC50 values over several cancer cell lines that belong to leukemia and colon cancer such as K-562, RPMI-8226, SR, COLO 205, HCT-116, HCT-15, HT29, KM12, and SW-620 cell lines. Compounds 1e and 1i induced apoptosis in K-562 leukemia cells in a dose-dependent manner. Compound 1i showed the highest cytotoxic activity with IC50 value of 200 nM against HT29 cell line. In addition, compounds 1e and 1i were tested against normal breast cells (HME1) and normal skin fibroblast cells (F180) and the results revealed that the compounds are safe toward normal cells compared to cancers cells. Enzymatic assays against NPP1-3 and carbonic anhydrases II, IX, and XII were performed to investigate the possible molecular target(s) of compounds 1e and 1i. Furthermore, a molecular docking study was performed to predict the binding modes of compounds 1e and 1i in the active site of the most sensitive enzymes subtypes.

Cytotoxic effects of halogenated tin phosphinoyldithioformate complexes against several cancer cell lines

Organotin complexes are studied as promising alternatives to the anticancer drug cisplatin. We report two monoorganotin(IV) complexes based on a dibenzyl phosphinoyldithioformate (H-DBPTF) ligand, containing either bromide (Sn-DBPTF-1) or chloride (Sn-DBPTF-2) anions. The complexes were characterized by standard analytical techniques and the structural details of these complexes were elucidated by single crystal X-ray diffraction. Sn-DBPTF-1 was cytotoxic at IC50 <10 μg mL-1 against cancer cell lines A549 (lung cancer), Aspc-1 (pancreatic cancer), OVCAR-3 (ovarian cancer), T-47D (breast cancer) and HCT116 (colon cancer), and breast epithelial stem cell line D492. The non-tumorigenic breast epithelial cell line MCF-10 was less sensitive at IC50 = 22 μg mL-1. Sn-DBPTF-2 had limited cytotoxic effect at IC50 13-37 μg mL-1. Sn-DBPTF-1 induced apoptosis and double-strand DNA breaks. Cell cycle arrest in G2 occurred in HCT116 and accumulation in G1 in Aspc-1. The results indicate that the basic effect of Sn-DBPTF-1 is to induce DNA damage, leading to apoptosis and cell cycle arrest depending on the cell line.

Metal incorporated aminothiazole-derived compounds: synthesis, density function theory analysis, in vitro antibacterial and antioxidant evaluation

The present study advocates the combined experimental and computational study of metal-based aminothiazole-derived Schiff base ligands. The structure and electronic properties of ligands have been experimentally studied by spectroscopic methods (UV-Vis, FT-IR, ¹H-NMR and ¹³C-NMR), mass spectrometry, elemental analysis and theoretically by density function theory (DFT). Computational calculations employing the B3LYP/6-31 + G(d,p) functional of DFT were executed to explore the optimized geometrical structures of ligands along with geometric parameters, molecular electrostatic potential (MEP) surfaces and frontier molecular orbital (FMO) energies. Global reactivity parameters estimated from FMO energy gaps signified the bioactive nature of ligands. The synthesized ligands were used for chelation with 3d-transition metals [VO(IV), Cr(III), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)] in 1 : 2 (metal : ligand) molar ratio. The spectral and magnetic results confirmed the formation of octahedral geometry around all the divalent and trivalent metal centres, whereas the tetravalent vanadyl centres were confirmed to have square-pyramidal geometry. All the as-synthesized compounds were investigated for in vitro antibacterial potential against two Gram-negative (Salmonella typhimurium and Escherichia coli) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacteria. Antibacterial assay results displayed pronounced activity, and their activity is comparable to that of a standard drug (streptomycin). The antioxidant potential of these compounds was assessed by employing diphenyl picryl hydrazide radical scavenging activity. The results displayed that all the metal chelates have exhibited more bioactivity in contrast with free ligands. The chelation was the main reason for their enhanced bioactivity. These results indicated that the thiazole metal-based compounds could be exploited as antioxidant and antimicrobial candidates.

DNA Binding and DNA Cleavage Activities of Newly Synthesized CoII and CuII Complexes of a β-Cyclodextrin Based Azo-Functionalized Schiff Base

Two water soluble complexes with CoII and CuII ions were synthesized using a novel β-cyclodextrin based azo-functionalized Schiff base as a ligand. The Schiff base and its metal complexes were characterized by different physico-chemical and spectroscopic methods. From the analyses of the experimental data, distorted octahedral geometry has been assigned for both the metal complexes. The binding interactions between the metal complexes and DNA were investigated by means of a thermal denaturation study and viscosity measurements as well as by electronic absorption and fluorescence spectroscopy. The DNA cleavage efficacy of the metal complexes was also studied by agarose gel electrophoresis using pBR DNA. These studies revealed that both the metal complexes followed an intercalative mode of binding to calf thymus (CT)-DNA and also effectively cleaved the supercoiled pBR DNA. The CoII complex, however, more efficiently cleaved CT-DNA than the CuII complex as much as the experimental results are concerned.

Natural and synthetic retinoid X receptor ligands and their role in selected nuclear receptor action

Important key players in the regulatory machinery within the cells are nuclear retinoid X receptors (RXRs), which compose heterodimers in company with several diverse nuclear receptors, playing a role as ligand inducible transcription factors. In general, nuclear receptors are ligand-activated, transcription-modulating proteins affecting transcriptional responses in target genes. RXR molecules forming permissive heterodimers with disparate nuclear receptors comprise peroxisome proliferator-activated receptors (PPARs), liver X receptors (LXRs), farnesoid X receptor (FXR), pregnane X receptor (PXR) and constitutive androstan receptor (CAR). Retinoid receptors (RARs) and thyroid hormone receptors (TRs) may form conditional heterodimers, and dihydroxyvitamin D₃ receptor (VDR) is believed to form nonpermissive heterodimer. Thus, RXRs are the important molecules that are involved in control of many cellular functions in biological processes and diseases, including cancer or diabetes. This article summarizes both naturally occurring and synthetic ligands for nuclear retinoid X receptors and describes, predominantly in mammals, their role in molecular mechanisms within the cells. A focus is also on triorganotin compounds, which are high affinity RXR ligands, and finally, we present an outlook on human microbiota as a potential source of RXR activators. Nevertheless, new synthetic rexinoids with better retinoid X receptor activity and lesser side effects are highly required.

Antiproliferative activity of cycloalkanecarboxamide derivatives possessing sulfonate or sulfamate moiety

A series of cycloalkanecarboxamide-containing sulfonate and sulfamate derivatives were prepared, and their antiproliferative activity was tested against NCI-60 cancer cell lines panel. Compound 1f possessing cyclohexyl and p-(tert-butyl)benzenesulfonate moieties was the most active among all the target compounds. It exerted broad-spectrum anticancer activity against all the nine cancer types involved in the NCI-60 panel. Additionally, compound 1g containing cyclohexyl and p-fluorobenzenesulfonate moieties was the most potent against HT29 colon cancer cell line (IC₅₀ = 4.73 µM) with selectivity index more than 4.23 towards HT29 than normal fibroblasts. It exerts its antiproliferative activity against HT29 through the induction of apoptosis (increasing caspase 3/7 activity) but not necrosis. Structure-activity relationship studies are presented in detail.

Novel triorganotin complexes based on phosphonic acid ligands: Syntheses, structures and in vitro cytostatic activity

Six novel organotin phosphonate complexes, [(Me₃Sn)₄(HL¹)₄]_n1, [(Me₃Sn)₂(HL²)₂]_n2, [(Me₃Sn)₂L³(H₂O)]_n3, [(Ph₃Sn)(HL¹)]₆4, [(Ph₃Sn)₂L²]_n5 and [(Ph₃Sn)₂L³]₆6, derived from phosphonic acid ligands [NaHL¹ = 1-C₁₀H₇OPO₂(OH)Na, H₂L² = 1-C₁₀H₇PO(OH)₂, H₂L³ = 2-C₁₀H₇PO(OH)₂], have been synthesized and characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C, ³¹P and ¹¹⁹Sn) spectroscopy and X-ray crystallography. The structural analysis reveals that complexes 1 and 5 display 1D infinite zig-zag chain structures, and complex 2 shows 1D right-handed helical chain structure, while complex 3 displays 1D left-handed helical chain structure. Complexes 4 and 6 are 24-membered macrocyclic rings interconnected by P, O and Sn atoms. Additionally, the molecules of complexes 1 and 3 are further linked through intermolecular π···π and O-H···O interaction into supramolecular structures, respectively. Furthermore, we preliminarily estimated in vitro cytostatic activity of complexes 1-6 against the human cervix tumor cells (HeLa), human hepatocellular carcinoma cells (HepG-2) and human normal breast cells (HBL-100). Importantly, the anti-proliferative properties and possible pathway of complex 6 are investigated, and the results demonstrate that complex 6 could induce apoptotic cell death via an overload of intracellular reactive oxygen species (ROS) levels and the dysfunctional depolarization of mitochondrial membranes.

Structure and bonding in triorganotin chlorides: a perspective from energy decomposition analysis

The Sn-Cl chemical bond of four organotin halides (Me₃SnCl, Et₃SnCl, Bu₃SnCl, and Ph₃SnCl) was studied by using relativistic density functional theory in combination with a quantitative energy decomposition analysis to explain the formation of charged species. The σ orbital is the dominant contributor to the stabilization of the Sn-Cl bond, and the π-orbital interactions also have a significant contribution to the stabilization of Ph₃Sn⁺ cation when the aromatic groups are bonded to the tin atom. The aromaticity of the phenyl groups delocalizes the positive charge, donating electrons to tin atom by conjugation. Although Me₃SnCl and Ph₃SnCl are constituted by groups which the size of the substituents is different, the interaction energies obtained with the energy decomposition analysis present similar values, which also occur with the thermodynamic parameters. Graphical abstract Organotin compounds have widely studied as a potential antitumoral agent. The mechanism in triorganotin compounds includes the formation of cation species, R₃Sn⁺. This article studies the influence of the R groups on the rupture of Sn-Cl bond using the fragment analysis and quantitative energy decomposition analysis.

Syntheses, Structures, and Catalytic Hydrocarbon Oxidation Properties of N-Heterocycle-Sulfonated Schiff Base Copper(II) Complexes

Reaction of the o-[(o-hydroxyphenyl)methylideneamino]benzenesulfonic acid (H2L) (1) with CuCl2·2H2O in the presence of pyridine (py) leads to [Cu(L)(py)(EtOH)] (2) which, upon further reaction with 2,2’-bipyridine (bipy), pyrazine (pyr), or piperazine (pip), forms [Cu(L)(bipy)]·MeOH (3), [Cu2(L)2(μ-pyr)(MeOH)2] (4), or [Cu2(L)2(μ-pip)(MeOH)2] (5), respectively. The Schiff base (1) and the metal complexes (2–5) are stabilized by a number of non-covalent interactions to form interesting H-bonded multidimensional polymeric networks (except 3), such as zigzag 1D chain (in 1), linear 1D chain (in 2), hacksaw double chain 1D (in 4) and 2D motifs (in 5). These copper(II) complexes (2–5) catalyze the peroxidative oxidation of cyclic hydrocarbons (cyclooctane, cyclohexane, and cyclohexene) to the corresponding products (alcohol and ketone from alkane; alcohols, ketone, and epoxide from alkene), under mild conditions. For the oxidation of cyclooctane with hydrogen peroxide as oxidant, used as a model reaction, the best yields were generally achieved for complex 3 in the absence of any promoter (20%) or in the presence of py or HNO3 (26% or 30%, respectively), whereas 2 displayed the highest catalytic activity in the presence of HNO3 (35%). While the catalytic reactions were significantly faster with py, the best product yields were achieved with the acidic additive.

Triphenyltin(IV) acylhydrazone compounds: Synthesis, structure and bioactivity

Four new triphenyltin(IV) acylhydrazone compounds of the type Ph₃SnCH₂CH₂CONHN=R (where Ph = phenyl; R = isopropyl, isobutyl, cyclopentyl and cyclooctyl) were synthesized and characterized by elemental analysis, infrared spectrum (IR), nuclear magnetic resonance spectrum (NMR) and mass spectrum (MS). The crystal structures were determined and showed that tin atoms were four-coordinated and adopted a pseudo-tetrahedron configuration. Tin(IV) compounds show excellent bovine serum albumin (BSA) binding properties, and can oxidize nicotinamide-adenine dinucleotid (NADH) to generate reactive oxygen species (ROS), which inducing apoptosis effectively. Bioassay results indicated that tin(IV) compounds have stronger cytotoxic activity against A549 human lung cancer cells compared with cis-platin used clinically, and showing some selectivity.

Packing polymorphism in 3-amino-2-pyrazinecarboxylate based tin(ii) complexes and their catalytic activity towards cyanosilylation of aldehydes

3-Amino-2-pyrazinecarboxylic acid is used to synthesize two new mononuclear interconvertible packing polymorphs of tin(ii) which act as heterogeneous catalysts for the cyanosilylation of aldehydes with trimethylsilyl cyanide.

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.

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.