Synthesis, anticancer activities, interaction with DNA and mitochondria of manganese complexes

Small Molecule Interactions with Biomacromolecules: DNA Binding Interactions of a Manganese(III) Schiff Base Complex with Potential Anticancer Activities

A manganese(III) complex, [MnIII(L)(SCN)(enH)](NO3)·H2O (1•H2O) (H2L = 2-((E)-(2-((E)-2-hydroxy-3-methoxybenzylidene-amino)-ethyl-imino)methyl)-6-methoxyphenol), has been synthesized and characterized by single-crystal X-ray diffraction analysis. The interaction of 1•H2O with DNA was studied by monitoring the decrease in absorbance of the complex at λ = 324 nm with the increase in DNA concentration, providing an opportunity to determine the binding constant of the 1•H2O-ct-DNA complex as 5.63 × 103 M-1. Similarly, fluorescence titration was carried out by adding ct-DNA gradually and monitoring the increase in emission intensity at 453 nm on excitation at λex = 324 nm. A linear form of the Benesi-Hildebrand equation yields a binding constant of 4.40 × 103 M-1 at 25 °C, establishing the self-consistency of our results obtained from absorption and fluorescence titrations. The competitive displacement reactions of dyes like ethidium bromide, Hoechst, and DAPI (4',6-diamidine-2'-phenylindole dihydrochloride) from dye-ct-DNA conjugates by 1•H2O were analyzed, and the corresponding KSV values are 1.05 × 104, 1.25 × 104, and 1.35 × 104 M-1 and the Kapp values are 2.16 × 103, 8.34 × 103, and 9.0 × 103 M-1, from which it is difficult to infer the preference of groove binding over intercalation by these DNA trackers. However, the molecular docking experiments and viscosity measurement clearly indicate the preference for minor groove binding over intercalation, involving a change in Gibbs free energy of -8.56 kcal/mol. The 1•H2O complex was then evaluated for its anticancer potential in breast cancer MCF-7 cells, which severely abrogates the growth of the cells in both 2D and 3D mammospheres, indicating its promising application as an anticancer drug through a minor groove binding interaction with ct-DNA.

Interactions of Mn complexes with DNA: the relevance of therapeutic applications towards cancer treatment

Manganese (Mn) is one of the most significant bio-metals that helps the body to form connective tissue, bones, blood clotting factors, and sex hormones. It is necessary for fat and carbohydrate metabolism, calcium absorption, blood sugar regulation, and normal brain and nerve functions. It accelerates the synthesis of proteins, vitamin C, and vitamin B. It is also involved in the catalysis of hematopoiesis, regulation of the endocrine level, and improvement of immune function. Again, Mn metalloenzymes like arginase, glutamine synthetase, phosphoenolpyruvate decarboxylase, and Mn superoxide dismutase (MnSOD) contribute to the metabolism processes and reduce oxidative stress against free radicals. Recent investigations have revealed that synthetic Mn-complexes act as antibacterial and antifungal agents. As a result, chemists and biologists have been actively involved in developing Mn-based drugs for the treatment of various diseases including cancer. Therefore, any therapeutic drugs based on manganese complexes would be invaluable for the treatment of cancer/infectious diseases and could be a better substitute for cisplatin and other related platinum based chemotherapeutic drugs. From this perspective, attempts have been made to discuss the interactions and nuclease activities of Mn(II/III/IV) complexes with DNA through which one can evaluate their therapeutic applications.

Syntheses, Structural Characterization, and Cytotoxicity Assessment of Novel Mn(II) and Zn(II) Complexes of Aroyl-Hydrazone Schiff Base Ligand

This work describes the syntheses, structural characterization, and biological profile of Mn(II)- and Zn(II)-based complexes 1 and 2 derived from the aroyl-hydrazone Schiff base ligand (L1). The synthesized compounds were thoroughly characterized by elemental analysis, Fourier transform infrared spectroscopy (FTIR), UV-vis, electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), and single-crystal X-ray diffraction (s-XRD). Density functional theory (DFT) studies of complexes 1 and 2 were performed to ascertain the structural and electronic properties. Hirshfeld surface analysis was used to investigate different intermolecular interactions that define the stability of crystal lattice structures. To ascertain the therapeutic potential of complexes 1 and 2, in vitro interaction studies were carried out with ct-DNA and bovine serum albumin (BSA) using analytical and multispectroscopic techniques, and the results showed more avid binding of complex 2 than complex 1 and L1. The antioxidant potential of complexes 1 and 2 was examined against the 2,2-diphenyl picrylhydrazyl (DPPH) free radical, which revealed better antioxidant ability of the Mn(II) complex. Moreover, the antibacterial activity of synthesized complexes 1 and 2 was tested against Gram-positive and Gram-negative bacteria in which complex 2 demonstrated more effective bactericidal activity than L1 and complex 1 toward Gram-positive bacteria. Furthermore, the in vitro cytotoxicity assessment of L1 and complexes 1 and 2 was carried out against MDA-MB-231 (triple negative breast cancer) and A549 (lung) cancer cell lines. The cytotoxic results revealed that the polymeric Zn(II) complex exhibited better and selective cytotoxicity against the A549 cancer cell line as was evidenced by its low IC₅₀ value.

Synthesis of Mn-ofloxacin complex, experimental and in silico DNA binding evaluation, biological activity assessment

Metal-fluoroquinolones have more antibacterial and cytotoxic effects compared to free fluoroquinolones. In this work, a bidentated Mn (II) complex with ofloxacin (MOC) was synthesized and its cytotoxicity activity, oxidative stress and DNA binding were studied. Anti- proliferative and cytotoxic tests revealed that MOC exhibits better anti proliferative and cytotoxic activities compared to OFL which was attributed to the more interaction of MOC with DNA. Therefore, the interaction of MOC with DNA was investigated by using voltammetry, UV-Vis, fluorescence, and in silico methods. The results revealed that MOC interacts with DNA via electrostatic and outside hydrogen binding via minor groove. The proposed DNA binding modes may support the greater in-vitro cytotoxicity of MOC compared to OFL alone.

Manganese Schiff Base Complexes, Crystallographic Studies, Anticancer Activities, and Molecular Docking

Choice of ligands is significant to successful synthesis of metal complexes (coordination compounds). This study reports the use of Schiff base as the right ligand to control the poor bioavailability and neurodegenerative toxicity challenges of manganese ion. In line with this study, document analysis was used as the methodological approach to evaluate the significance of Schiff base ligands in easing these manganese’s challenges and aligning the resultant coordination compounds (manganese Schiff base complexes) as therapeutic agents in anticancer studies. Report also involves crystallographic studies where single crystal X-ray crystallography was used as a chemical characterization technique. In addition, molecular docking studies, MOE2008, and AutoDock software were used to reveal the mode of interaction between the Schiff base and the manganese(II) and (III) ions, as well as scrutinizing the biological efficacy of the manganese(II) and manganese(III) Schiff bases coordination compounds as anticancer agents against some anticancer cell lines. Conclusion drawn was that manganese(II) and manganese(III) Schiff bases coordination compounds gave more active and potent activities than the corresponding Schiff bases. As a result, challenges of neurodegenerative toxicity and poor bioavailability of manganese ion were overcome, and the chelation therapy was fulfilled. Results from single crystal X-ray crystallography confirmed the successful synthesis of manganese(II) and manganese(III) Schiff bases coordination compounds and revealed the mechanism of reaction, while the molecular docking buttressed the biological activities of the Schiff base ligand and manganese Schiff base coordination compounds by portraying the structure activity relationship (SAR) between either Schiff base or the manganese Schiff base coordination compounds and the virtual cancer cell line (receptor protein), where hits were obtained for lead optimizations.

Well-Defined Phosphine-Free Manganese(II)-Complex-Catalyzed Synthesis of Quinolines, Pyrroles, and Pyridines

Herein, we report a simple, phosphine-free, and inexpensive catalytic system based on a manganese(II) complex for synthesizing different important N-heterocycles such as quinolines, pyrroles, and pyridines from amino alcohols and ketones. Several control experiments, kinetic studies, and DFT calculations were carried out to support the plausible reaction mechanism. We also detected two potential intermediates in the catalytic cycle using ESI-MS analysis. Based on these studies, a metal-ligand cooperative mechanism was proposed.

Transcriptome Analysis and SNP Identification Reveal That Heterologous Overexpression of Two Uncharacterized Genes Enhances the Tolerance of Magnaporthe oryzae to Manganese Toxicity

Manganese is a crucial trace element that constitutes the cofactors of many enzymes. However, excessive Mn2+ can be toxic for both prokaryotes and eukaryotes. The mechanism of fungal genetics and metabolism in response to Mn2+ stress remains understudied, warranting further studies. Magnaporthe oryzae is well-established as the most destructive pathogen of rice. A field strain, YN2046, more sensitive to Mn2+ toxicity than other strains, was obtained from a previous study. Herein, we explored the genetic mechanisms of Mn2+ sensitivity in YN2046 through comparative transcriptomic analyses. We found that many genes previously reported to participate in Mn2+ stress were not regulated in YN2046. These non-responsive genes might cause Mn2+ sensitivity in YN2046. Weight gene correlation network analysis (WGCNA) was performed to characterize the expression profile in YN2046. Some overexpressed genes were only found in the Mn2+ tolerant isolate YN125. Among these, many single nucleotide polymorphism (SNP) were identified between YN125 and YN2046, which might disrupt the expression levels of Mn responsive genes. We cloned two uncharacterized genes, MGG_13347 and MGG_16609, from YN125 and transformed them to YN2046 with a strong promoter. Our results showed that the heterologous overexpression of two genes in YN2046 restored its sensitivity. Transcriptomic and biochemical analyses were performed to understand Mn tolerance mechanisms mediated by the two heterologous overexpressed genes. Our results showed that heterologous overexpression of these two genes activated downstream gene expression and metabolite production to restore M. oryzae sensitivity to Mn, implying that SNPs in responsive genes account for different phenotypes of the two strains under Mn stress. IMPORTANCE Heavy metals are used for fungicides as they target phytopathogen in multiple ways. Magnaporthe oryzae is the most destructive rice pathogen and is threatening global rice production. In the eukaryotes, the regulation mechanisms of Mn homeostasis often focus on the posttranslation, there were a few results about regulation at transcript level. The comparative transcriptome analysis showed that fewer genes were regulated in the Mn-sensitive strain. WGCNA and SNP analyses found that mutations in promoter and coding sequence regions might disrupt the expression of genes involved in Mn detoxification in the sensitive strain. We transferred two unannotated genes that were cloned from the Mn-tolerant strain into a sensitive strain with strong promoters, and the transformants exhibited an enhanced tolerance to Mn2+ toxicity. Transcriptome and biochemistry results indicated that heterologous overexpression of the two genes enhanced the tolerance to Mn toxicity by reactivation of downstream genes in M. oryzae.

Manganese(II) complexes of substituted salicylaldehydes and α-diimines: Synthesis, characterization and biological activity

The interaction of Mn⁺² with substituted salicylaldehydes (X-saloH) led to the formation of five manganese(II) complexes formulated as [Μn(X-salo)₂(MeOH)₂]. When the reactions took place in the presence of an α-diimine such as 2,2'-bipyridine, 1,10-phenanthroline or 2,2'-bipyridylamine, five manganese(II) complexes of the formula [Mn(X-salo)₂(α-diimine)] were isolated. The characterization of the complexes was accomplished by various spectroscopic techniques and single-crystal X-ray crystallography. The antioxidant activity of the compounds was evaluated via the scavenging of 1,1-diphenyl-picrylhydrazyl, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and hydroxyl free radicals. The antibacterial activity of the complexes was tested in vitro against Staphylococcus aureus and Xanthomonas campestris bacterial strains and was found moderate. Diverse techniques were employed to examine the interaction of the complexes with calf-thymus DNA which showed intercalation as the most possible interaction mode. The affinity of the complexes for bovine serum albumin was investigated by fluorescence emission spectroscopy and the binding constants were determined.

Bovine serum albumin interactive one dimensional hexanuclear manganese(iii) complex: synthesis, structure, binding and molecular docking studies

A hexanuclear Mn(III) complex was synthesized and structiurally characterized which exhibits fluorescence quenching of BSA probably through site selective binding at the mouth of site I in subdomain IIA.

Mitochondria-Targeting Anticancer Metal Complexes

Background:

Since the serendipitous discovery of the antitumor activity of cisplatin there has been a continuous surge in studies aimed at the development of new cytotoxic metal complexes. While the majority of these complexes have been designed to interact with nuclear DNA, other targets for anticancer metallodrugs attract increasing interest. In cancer cells the mitochondrial metabolism is deregulated. Impaired apoptosis, insensitivity to antigrowth signals and unlimited proliferation have been linked to mitochondrial dysfunction. It is therefore not surprising that mitochondria have emerged as a major target for cancer therapy. Mitochondria-targeting agents are able to bypass resistance mechanisms and to (re-) activate cell-death programs.

Methods:

Web-based literature searching tools such as SciFinder were used to search for reports on cytotoxic metal complexes that are taken up by the mitochondria and interact with mitochondrial DNA or mitochondrial proteins, disrupt the mitochondrial membrane potential, facilitate mitochondrial membrane permeabilization or activate mitochondria-dependent celldeath signaling by unbalancing the cellular redox state. Included in the search were publications investigating strategies to selectively accumulate metallodrugs in the mitochondria.

Results:

This review includes 241 references on antimitochondrial metal complexes, the use of mitochondria-targeting carrier ligands and the formation of lipophilic cationic complexes.

Conclusion:

Recent developments in the design, cytotoxic potency, and mechanistic understanding of antimitochondrial metal complexes, in particular of cyclometalated Au, Ru, Ir and Pt complexes, Ru polypyridine complexes and Au-N-heterocyclic carbene and phosphine complexes are summarized and discussed.

Substituted effect on some water-soluble Mn(II) salen complexes: DNA binding, cytotoxicity, molecular docking, DFT studies and theoretical IR & UV studies

Based on the importance of central metal complexes to interact with DNA, in this research focused on synthesis of some new water soluble Mn(II) complexes 1-4 which modified substituted in ligand at the same position with N, Me, H, and Cl. These complexes were isolated and characterized by elemental analyses, FT-IR, electrospray ionization mass spectrometry (ESI-MS) and UV-vis spectroscopy. DNA binding studies had been studied by using circular dichroism (CD) spectroscopy, UV-vis absorption spectroscopy, cyclic voltammetry (CV), viscosity measurements, emission spectroscopy and gel electrophoresis which proposed the metal buildings go about as effective DNA binders were studied in the presence of Fish-DNA (FS-DNA) which showed the highest binding affinity to DNA with hydrophobic and electron donating substituent. Cell toxicity assays against two human leukemia (Jurkat) and breast cancer (MCF-7) cell lines showed that the complex 3 exhibited a remarkable effects equal to a famous anticancer drug, cisplatin that high cytotoxic activity strongly depend on the hydrophobic substituted ligand. In the theoretical part, density functional theory (DFT) was performed to optimize the geometry of complexes through IR and UV spectra of the complexes that ligand substitution did not affect the geometry and theoretical IR and UV spectra showed good resemblance to the experimental data. The docking studies calculated the lowest-energy between complexes and DNA with the minor grooves mode.

A manganese-salen complex as dipeptidyl peptidase IV inhibitor for the treatment of type 2 diabetes

A manganese Schiff base complex with N,N'-1,2-phenylenediamine-bis(salicyladimine) was synthesized and characterized by X-ray crystallography. This complex was administered intragastrically to alloxan-diabetic mice 3 weeks. In vivo tests showed that the complex significantly lowered serum glucose levels in alloxan-diabetic mice at doses of 77 mg V kg^-1. Meanwhile, this complex was investigated as dipeptidyl peptidase IV (DPP-IV) inhibitor for the treatment of type 2 diabetes. The compound exhibit moderate inhibition against DPP-IV and possessed an IC₅₀ value of 30 μM. Lineweaver-Burk transformation of the inhibition kinetics data demonstrated that it was a noncompetitive inhibitor of DPP-IV and Ki value was 136.3 μM. Moreover, molecular modeling studies suggested that the complex could fit well within the active-site cleft of DPP-IV. An acute toxicity study showed that animals treated intragastically with complex 1 at a dose of 5.0 g/kg did not show any significantly abnormal signs. These preliminary results suggest that the manganese Schiff base complex can induce a hypoglycemic effect in alloxan-diabetic mice.

In vitro and in silico study of the biological activity of manganese(III) inverse-[9-MC-3]-metallacrowns and manganese(II) complexes with the anti-inflammatory drugs diclofenac or indomethacin

In the present contribution, the biological properties of four manganese complexes with the non-steroidal anti-inflammatory drugs sodium diclofenac (Nadicl) or indomethacin (Hindo) in the presence or absence of salicylaldoxime (Η₂sao), i.e. [Μn₆(O)₂(dicl)₂(sao)₆(CH₃OH)₆] 1, [Μn₆(O)₂(indo)₂(sao)₆(H₂O)₄], 2, [Μn(dicl)₂(CH₃OH)₄], 3, and [Μn(indo)₂(CH₃OH)₄], 4 are presented. More specifically, the in vitro cytotoxic effects of the complexes were evaluated against three cancer cell lines (HeLa, MCF-7 and A549 cells) as well as their combinatory activity with the well-known chemotherapeutic drugs irinotecan, cisplatin, paclitaxel and 5-fluorouracil. The biological activity of the complexes was investigated in vitro by studying their affinity to calf-thymus DNA and their binding towards bovine or human serum albumin (HSA). Molecular docking simulations on the crystal structure of HSA and human estrogen receptor alpha (hERa) were employed in order to study in silico the ability of the studied complexes to bind to these proteins.

A step-ladder manganese(iii) metallacrown hosting mefenamic acid and a manganese(ii)–mefanamato complex: synthesis, characterization and cytotoxic activity

Manganese complexes of mefenamic acid in the presence or absence of salicylaldoxime have been evaluated for their cytotoxic activity.

Manganese(ii) complexes with the non-steroidal anti-inflammatory drugs naproxen and mefenamic acid: synthesis, structure, antioxidant capacity, and interaction with albumins and DNA

The structure, antioxidant activity and interaction with DNA and albumins of a series of manganese(ii) complexes of mefenamic acid or naproxen are presented herein.

Inhibitory effects of different substituted transition metal-based krebs-type sandwich structures on human hepatocellular carcinoma cells

POMs induced apoptosis in HepG2 cells, which indicated sub-G1 hypodiploid cell population before the G1 phase via flow cytometry. POM3 showed the highest apoptotic rate of these POMs. This reveals the structure–function relationship of bioactive transition metal ions.

A novel [Mn2(μ-(C6H5)2CHCOO)2(bipy)4](bipy)(ClO4)2 complex loaded solid lipid nanoparticles: synthesis, characterization and in vitro cytotoxicity on MCF-7 breast cancer cells

Manganese (Mn)-based complexes have been drawing attention due to the fact that they are more effective than other metal complexes. However, the use of Mn(II)-based complexes in medicine remains limited because of certain side effects. The aim of this study was to investigate the cytotoxic and apoptotic effects of a novel Mn(II) complex [Mn₂(μ-(C₆H₅)₂CHCOO)₂(bipy)₄](bipy)(ClO₄)₂ and Mn(II) complex loaded solid lipid nanoparticles (SLNs) on MCF-7 and HUVEC control cells. The average diameter of Mn(II) complex was about 1120 ± 2.43 nm, while the average particle size of Mn(II) complex-SLNs was ∼340 ± 2.27 nm. The cytotoxic effects of Mn(II) complex and Mn(II)-SLNs were 86.8 and 66.4%, respectively (p < .05). Additionally, both Mn(II) complex (39.25%) and Mn(II)-SLNs (38.05%) induced apoptosis and increased the arrest of G₀/G₁ phase. However, Mn(II) complex exerted toxic effects on the HUVEC control cell (63.4%), whereas no toxic effects was observed when treated with Mn(II)-SLNs at 150 μM. As a consequence, SLNs might be potentially used for metal-based complexes in the treatment of cancer due to reducing size and toxic effects of metal-based complexes.

Mn(ii) silver-aptamer clusters for targeted MR imaging of tumors

Hypoxia-inducible factor (HIF) highly expressed in most of the cancer cells. The Mn(ii)-aptamer based nanoclusters with 3D structures would be HIF-aptamer based targeted magnetic resonance imaging agents for cancer MRI diagnosis. Herein, a new class of contrast agent Mn(ii) silver-aptamer clusters (AdpaMn@DNA-Ag-DNA_G1) were constructed based on the assembly of DNA-mediated Ag nanoclusters (DNA-AgNCs) with the Mn(ii) complex (AdpaMn) and DNA_G1, the recognition sequence of GLUT-1. Then, the Mn(ii) silver-aptamer clusters (AdpaMn@DNA-Ag-DNA_G1) are used as the MRI agents both in vitro and in vivo. The results show that the MRI signal is clearly presented in the tumor position. Consequently, the Mn(ii) silver-aptamer clusters can be used as a new class of contrast agents for targeted MR imaging of tumors.

Cytotoxicity of Manganese (III) Complex in Human Breast Adenocarcinoma Cell Line Is Mediated by the Generation of Reactive Oxygen Species Followed by Mitochondrial Damage

Manganese (Mn) complexes are widely studied because of their important catalytic properties in synthetic and biochemical reactions. A Mn (III) complex of an amidoamine ligand was synthesized using a tetradentate amidoamine ligand. In this study, the Mn (III) complex was evaluated for its biological activity by measuring its cytotoxicity in human breast adenocarcinoma cell line (MCF-7). Cytotoxic effects of the Mn (III) complex were determined using established biomarkers in an attempt to delineate the mechanism of action and the utility of the complex as a potential anticancer drug. The Mn (III) complex induces cell death in a dose- and time-dependent manner as shown by microculture tetrazolium assay, a measure of cytotoxic cell death. Our results demonstrated that cytotoxic effects were significantly increased at higher concentrations of Mn (III) complex and with longer time of treatment. The IC50 (Inhibitor concentration that results in 50% cell death) value of Mn (III) complex in MCF-7 cells was determined to be 2.5 mmol/L for 24 hours of treatment. In additional experiments, we determined the Mn (III) complex–mediated cell death was due to both apoptotic and nonspecific necrotic cell death mechanisms. This was assessed by ethidium bromide/acridine orange staining and flow cytometry techniques. The Mn (III) complex produced reactive oxygen species (ROS) triggering the expression of manganese superoxide dismutase 1 and ultimately damaging the mitochondrial function as is evident by a decline in mitochondrial membrane potential. Treatment of the cells with free radical scavenger, N, N-dimethylthiourea decreased Mn (III) complex–mediated generation of ROS and attenuated apoptosis. Together, these results suggest that the Mn (III) complex–mediated MCF-7 cell death utilizes combined mechanism involving apoptosis and necrosis perhaps due to the generation of ROS.

Neuroprotection by Polynitrogen Manganese Complexes: Regulation of Reactive Oxygen Species-Related Pathways

Cell death in the central nervous system causes neurologic diseases, in which reactive oxygen species (ROS) play a critical role by either inducing cellular oxidative stress or by increasing the cell tolerance against insult. Neurologic diseases may potentially be treated by regulating ROS levels in a certain range with small molecules. We studied preconditioning with two polynitrogen manganese complexes (1 and 2) to regulate intracellular ROS levels in the protection of both the differentiated rat pheochromocytoma cell line (PC12 cells) and neurons against H₂O₂-induced apoptosis. Pre-treatment with the two complexes attenuated the cell apoptosis caused by H₂O₂. And the ROS-related neuroprotective mechanisms were explored. Both complexes activate the hypoxia inducible factor-related pathways and increase the cell adaptation to oxidative stress. Pre-treatment with complex 1 eliminated intracellular ROS, which also activated antioxidase system, while short-term incubation of complex 2, generated low levels of ROS leading to cell survival.

Cefepime, a fourth-generation cephalosporin, in complex with manganese, inhibits proteasome activity and induces the apoptosis of human breast cancer cells

Cefepime (FEP), which is a member of the fourth-generation cephalosporin class, has been extensively studied as a biochemical and antimicrobial reagent in recent years. Manganese (Mn) is important in the biochemical and physiological processes of many living organisms, and it is also high expressed in some tumor tissues. In the present study, we aimed to investigate the proteasome-inhibitory and anti-proliferative properties of 8 metal complexes (FEP‑Cu, FEP-Zn, FEP-Co, FEP-Ni, FEP-Cd, FEP-Cr, FEP-Fe, FEP-Mn) in MDA-MB‑231 human breast cancer cells. The FEP-Mn complex was found to be more potent in its ability to inhibit cell proliferation and proteasome activity than the other compounds tested. Moreover, the FEP-Mn complex inhibited proteasomal chymotrypsin-like (CT-like) activity and induced the apoptosis of breast cancer cells in a dose-and time-dependent manner. Furthermore, the MCF-10A cells were much less sensitive to the FEP complexes compared with the MDA-MB-231 breast cancer cells. These results demonstrated that the FEP-Mn(II) complex has the potential to act as a proteasome inhibitor and apoptosis inducer and therefore has possible future applications in cancer chemotherapy.

A comparative study of cytotoxicity and interaction with DNA/protein of five transition metal complexes with Schiff base ligands

Five transition metal complexes NiL(1)2 (1), CuL(1)2 (2), ZnL(1)2 (3), [MnL(1)2(N3)]n·nCH2Cl2 (4), CuL(2)2 (5) {HL(1)=3-{[2-(2-hydroxy-ethoxy)-ethylimino]-methyl}-naphthalen-2-ol, HL(2)=2-{[2-(2-hydroxy-ethoxy)-ethylimino]-methyl}-phenol} have been synthesized and fully characterized. In all of the complexes, the ligands coordinated to the metal ion in a negative fashion via O and N donor atoms. The X-ray structures of nickel complex 1 and copper complexes 2 and 5 are four-coordinated monomers and show slightly distorted square-planar geometry in the vicinity of the central metal atom. Zinc complex 3 exhibits a four-coordinated tetrahedral structure. Differently, manganese complex 4 reveals a six-coordinated octahedral structure, one-dimensional chain is linked by azide in the end-to-end mode. In vitro cytotoxicity of these complexes to various tumor cell lines was assayed by the MTT method. The results showed that most of these metal-Schiff base complexes exhibited enhanced cytotoxicity than Schiff base ligands, which clearly implied a positive synergistic effect. Moreover, these complexes appeared to be selectively active against certain cell lines. The interactions of these metal complexes with CT-DNA were investigated by UV-vis, fluorescence and CD spectroscopy, the results indicated that these complexes are metallointercalators and can interact with CT-DNA. The study of interaction between complexes and BSA indicated that all of the complexes could quench the intrinsic fluorescence of BSA in a static quenching process.

Tumor-targeting novel manganese complex induces ROS-mediated apoptotic and autophagic cancer cell death

In this study, the antitumor activity of the novel manganese (II) compound, Adpa-Mn {[(Adpa)Mn(Cl)(H(2)O)] (Adpa=bis(2-pyridylmethyl)amino-2-propionic acid)}, and its possible mechanisms of action were investigated. In vitro, the growth inhibitory effects of Adpa-Mn (with IC(50) values lower than 15 µM) on tumor cell lines were examined by MTT assay. We found that this compound was more selective against cancer cells than the popular chemotherapeutic reagent, cisplatin. We then found that Adpa-Mn achieved its selectivity against cancer cells through the transferrin (Tf)-transferrin receptor (TfR) system, which is highly expressed in tumor cells. Furthermore, Adpa-Mn induced both apoptosis and autophagy, as indicated by chromatin condensation, the activation of poly(ADP-ribose) polymerase (PARP), Annexin V/propidium iodide staining, an enhanced fluorescence intensity of monodansylcadaverine (MDC), as well as the elevated expression of the autophagy-related protein, microtubule-associated protein 1 light chain 3 (LC3). In addition, Adpa-Mn induced the generation of intracellular reactive oxygen species (ROS) and its anticancer effects were significantly reduced following pre-treatment with the antioxidant, N-acetyl cysteine, indicating that ROS triggered cell death. In vivo, the induction of apoptosis and autophagy in tumor tissue was confirmed following treatment with Adpa-Mn, which contributed to its significant antitumor activity against hepatocellular carcinoma (Hep-A cell) xenografts at 10 mg/kg. Taken together, these data suggest the possible use of Adpa-Mn as a novel anticancer drug.

Structure, antimicrobial activity, albumin- and DNA-binding of manganese(ii)–sparfloxacinato complexes

The manganese(ii)–sparfloxacinato complexes exhibit activity towards four bacteria and enhanced affinity for DNA and albumins in comparison to free sparfloxacin.

Synthesis, crystal structure, and biological activities of two chiral mononuclear Mn((III)) complexes

Two new chiral mononuclear Mn((III)) complexes, [MnL((R)) Cl (C2 H5 OH)]•C2 H5 OH () and [MnL((S)) (CH3 OH)2 ]Cl•CH3 OH (), {H2 L = (R,R)-or (S,S)-N,N'-bis-(2-hydroxy-1-naphthalidehydene)-cyclohexanediamine} were synthesized and characterized by various physicochemical techniques. Bond valence sum (BVS) calculations and the Jahn-Teller effect indicate that the Mn centers are in a +3 oxidation state. The statuses of the two complexes in the solution were confirmed as a pair of enantiomers by electrospray ionization, mass spectrometry (ESI-MS) spectrum. The binding ability of the complexes with calf thymus CT-DNA was investigated by spectroscopic and viscosity measurements. Both of the complexes could interact with CT-DNA via an intercalative mode with the order of (R-enantiomer) > (S-enantiomer). Under the physiological conditions, the two compounds exhibit efficient DNA cleavage activities without any external agent, which also follows the order of R-enantiomer > S-enantiomer. Interestingly, the concentration-dependent DNA cleavage experiments indicate an optimal concentration of 17.5 μM. In addition, the interaction of the compounds with bovine serum albumin (BSA) was also investigated, which indicated that the complexes could quench the intrinsic fluorescence of BSA by a static quenching mechanism.