Ruthenium(II) polypyridyl complexes with benzothiophene and benzimidazole derivatives: Synthesis, antitumor activity, solution studies and biospeciation.

With the aim to incorporate pharmacophore motifs into the Ru(II)-polypyridyl framework, compounds [Ru(II)(1,10-phenantroline)2(2-(2-pyridyl)benzo[b]thiophene)](CF3SO3)2 (1) and [Ru(II)(1,10-phenantroline)2(2-(2-pyridyl)benzimidazole)](CF3SO3)2 (2) were prepared, characterized and tested for their antitumor potential. The solid-state structure of the compounds was confirmed by single-crystal X-ray diffraction analysis. The solution behavior of both complexes was investigated, namely their solubility, stability, and lipophilicity in physiological mimetic conditions, as well as an eventual uptake by passive diffusion. In vitro anticancer activity of the complexes on ovarian and different colon cancer cells and apoptosis induction by the complexes were studied. A slow transformation process was observed for complex 1 in aqueous solution when exposed to sunlight, while complex 2 undergoes deprotonation (pKa = 7.59). The lipophilicity of this latter complex depends strongly on the pH and ionic strength. In contrast, 1 is rather hydrophilic under various conditions. Complex 1 was highly cytotoxic on Colo-205 human colon (IC50 = 7.87 µM) and A2780 ovarian (IC50 = 2.2 µM) adenocarcinoma cell lines, while 2 displayed moderate anticancer activity (30.9 µM and 18.0 µM, respectively). The complexes induced late apoptosis and necrosis. Only a weak binding of the complexes to human serum albumin, the main transport protein in blood serum, was found. However, a more significant binding to calf thymus DNA was observed in UV-visible titrations and fluorometric dye displacement studies. Detailed analysis of fluorescence lifetime data collected for the latter systems reveals not only the partial intercalation of the complexes, but goes beyond the usual simplified interpretations.

New ternary Fe(III)-8-hydroxyquinoline-reduced Schiff base complexes as selective anticancer drug candidates.

Due to the growing prevalence of cancer diseases, new therapeutic options are urgently needed, and drugs based on metal ions other than platinum are alternatives with exciting possibilities. We report the synthesis, characterization and biological effect of mixed-ligand Fe(III)-aminophenolate complexes derived from salicylaldehyde and L-tryptophan with quinoline derivatives as co-ligands, namely 8-hydroxyquinoline (8HQ), [Fe(L)(8HQ)(H2O)] (1) and its 5-cloro derivative (Cl8HQ), [Fe(L)(Cl8HQ)(H2O)] (2). The complex bearing the aminophenolate and lacking the quinoline co-ligand, [Fe(L)(Cl)(H2O)2] (3), was prepared for comparison. The analytical and spectroscopic characterization revealed that 1 and 2 are octahedral Fe(III) complexes with the aminophenolate acting as a dianionic tridentate ligand and 8HQ co-ligands as bidentate chelates. Spectroscopic techniques and molecular docking studies were used to evaluate the ability of these complexes to bind bovine serum albumin (BSA) and calf thymus DNA. Complex 2 [Fe(L)(Cl8HQ)(H2O)] was the one showing higher affinity for both biomolecules. Cell viability was assessed in breast, colorectal and bone human cancer cell lines. 1 and 2 were found to be more active than cisplatin in all cell lines tested. A non-tumoral fibroblast line (L929, mouse non-tumoral fibroblasts) was used to evaluate selectivity. The results evidence that 2 shows much higher selectivity than 1 in all cell lines tested, but particularly in bone cancer cells in which selectivity index (SI) values are 8.0 and 18.8 for 1 and 2, respectively.

New iron(III) anti-cancer aminobisphenolate/phenanthroline complexes: Enhancing their therapeutic potential using nanoliposomes.

Malignant melanoma is an aggressive and deadly form of skin cancer and novel and improved therapeutic options are needed. A promising strategy involves the use of metallodrugs combined with liposomes for targeted delivery to cancer cells. In this work, a family of iron(III) complexes was synthesized bearing a trianionic aminobisphenolate ligand (L) and phenanthroline-type co-ligands (NN). Four ternary iron complexes of general formula [Fe(L)(NN)] were obtained: [Fe(L)(amphen)] (1), [Fe(L)(phen)] (2), [Fe(L)(Clphen)] (3), and [Fe(L)(Mephen)] (4), as well as a fifth complex [Fe(L)(NEt3)(H2O)] (5) without the bidentate co-ligand. All complexes were characterized by analytic and spectroscopic techniques and demonstrated to be stable in aqueous environment. Complexes 1 and 2 were able to bind DNA and presented high cytotoxic activity towards human cancer cells. Complex 1 (IronC) was selected for incorporation into different liposomal formulations, which were fully characterized and screened against murine melanoma cells. The IronC liposomal formulation with the highest incorporation efficiency (∼95%) and a low IC50 value (7.1 ± 0.7 µM) was selected for in vivo evaluation. In a syngeneic murine melanoma model the liposomal formulation of IronC yielded the highest impairment on tumour progression when compared with the control, temozolomide, and with the iron complex in free form.

Experimental data on novel Fe(III)-complexes containing phenanthroline derivatives for their anticancer properties.

This dataset is related to the research article entitled "May iron(III) complexes containing phenanthroline derivatives as ligands be prospective anticancer agents?" [1]. It includes the characterization by UV-Vis absorption spectroscopy and magnetic techniques of a group of mixed ligand Fe(III) complexes bearing a tripodal aminophenolate ligand L2-, H2L = N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-N-(2-pyridylmethyl)amine, and different aromatic bases (NN = 2,2'-bipyridine [Fe(L)(bipy)]PF6 (1), 1,10-phenanthroline [Fe(L)(phen)]PF6 (2), or a phenanthroline derivative co-ligand: [Fe(L)(amphen)]NO3 (3), [Fe(L)(amphen)]PF6 (3a), [Fe(L)(Clphen)]PF6 (4), [Fe(L)(epoxyphen)]PF6 (5) (where amphen = 1,10-phenanthroline-5-amine, epoxyphen = 5,6-epoxy-5,6-dihydro-1,10-phenanthroline, Clphen = 5-chloro-1,10-phenanthroline), as well as [Fe(L)(EtOH)]NO3 (6), [Fe(phen)Cl3] (7) and [Fe(amphen)Cl3] (8). Data on their hydrolytic stability in physiological buffers is shown, as well as on their interaction with calf thymus DNA by spectroscopic tools. Additionally, the anticancer efficacy and the cellular death mechanisms activated in response to these drugs in HeLa, H1299 and MDA-MB-231 cells are provided.

Exploring the cytotoxic activity of new phenanthroline salicylaldimine Zn(II) complexes.

Zinc(II) complexes bearing N-salicylideneglycinate (Sal-Gly) and 1,10-phenanthroline (phen) or phenanthroline derivatives [NN = 5-chloro-1,10-phenanthroline, 5-amine-1,10-phenanthroline (amphen), 4,7-diphenyl-1,10-phenanthroline (Bphen) and 5,6-epoxy-5,6-dihydro-1,10-phenanthroline] are synthesized. Complexes formulated as [Zn(NN)2(H2O)2]2+(NN = phen and amphen), are also prepared. The cytotoxicity of the compounds is evaluated towards a panel of human cancer cells: ovarian (A2780), breast (MCF7) and cervical (HeLa), as well as non-tumoral V79 fibroblasts. All compounds display higher cytotoxicity than cisplatin (IC50 = 22.5 ±â€¯5.0 µM) towards ovarian cells, showing IC50values in the low micromolar range. Overall, all compounds show higher selectivity for the A2780 cells than for the non-tumoral cells and higher selectivity indexes (IC50(V79)/IC50(A2780) than cisplatin. [Zn(Sal-Gly)(NN)(H2O)] complexes induce caspase-dependent apoptosis in A2780 cells, except [Zn(Sal-Gly)(Bphen)(H2O)], one of the most cytotoxic of the series. The cellular uptake in the ovarian cells analyzed by Inductively Coupled Plasma mass spectrometry indicates different Zn distribution profiles. Transmission electronic microscopy shows mitochondria alterations and apoptotic features consistent with caspase activation; cells incubated with [Zn(Sal-Gly)(amphen)(H2O)] present additional nuclear membrane alterations in agreement with significant association with the nucleus. The increase of reactive oxygen species and lipid peroxidation forms could be related to apoptosis induction. [Zn(NN)2(H2O)2]2+complexes have high ability to bind DNA through intercalation/groove binding, and circular dichroism data suggests that the main type of species that interact with DNA is [Zn(NN)]2+. Studies varying the % of fetal bovine serum (1-15%) in cell media show that albumin binding decreases the complex activity, indicating that distinct speciation of Zn- and phen-containing species in cell media may affect the cytotoxicity.

New ternary iron(iii) aminobisphenolate hydroxyquinoline complexes as potential therapeutic agents.

In the quest for therapeutic iron-based metallodrugs, two new mixed-ligand iron(iii) complexes bearing the tripodal aminobisphenolate ligand N,N-bis(3,5-dimethyl-2-hydroxybenzyl)-N-(2-pyridylmethyl)amine (H2L) and hydroxyquinoline co-ligands, 8-hydroxyquinoline (8HQ) or 5-chloro-8-hydroxyquinoline (Cl8HQ), are synthesized, fully characterized and formulated as [Fe(L)(8HQ)] (1) and [Fe(L)(Cl8HQ)] (2), respectively. These high-spin Fe(iii) complexes are stable in aqueous solution in the presence of equimolar amounts of Bovine Serum Albumin (BSA), which indicates a likely binding interaction with the protein. In fact, binding constant log values at pH 7.4 for HSA of 5.08 and 6.35 were obtained for 1 and 2, respectively. Compounds 1 and 2 are cytotoxic against both human triple-negative breast adenocarcinoma (MDA-MB-231) and human cervical carcinoma (HeLa) cancer cells, and the activity is significantly improved by inclusion of the co-ligands 8HQ and Cl8HQ to the precursor complex Fe(L). Moreover, 1 and 2 are more active than 8HQ and Cl8HQ, particularly at lower incubation times tested, 24 and 48 h. Cells treated with the complexes display typical features of apoptosis as assessed by cellular morphology, DNA condensation and TUNEL analysis. COMET assays show that both drug candidates induce genomic damage in both cell lines. The complexes exhibit DNA cleavage activity and DNA damage that may be related to their ability to generate ROS. Overall, data supports that 1 and 2 are both active anticancer drug candidates within the low micromolar range. This is particularly interesting in the case of the breast MDA-MB-231 line, a model for triple-negative breast cancer that is an aggressive form of breast cancer, highly invasive and with limited treatment options and very poor prognosis. Furthermore, both complexes exhibited good anti-Mycobacterium tuberculosis activity, suggesting that 1 and 2 might have a wide spectrum of biological activity and justify further research.

May iron(III) complexes containing phenanthroline derivatives as ligands be prospective anticancer agents?

We report the design, synthesis and biological studies on a group of mixed ligand Fe(III) complexes as anti-cancer drug candidates, namely their interaction with DNA, cytotoxicity and mechanism(s) of action. The aim is to obtain stable, efficient and selective Fe-complexes to be used as anti-cancer agents with less damaging side effects than previously reported compounds. Five ternary Fe(III) complexes bearing a tripodal aminophenolate ligand L2-, H2L = N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-N-(2-pyridylmethyl)amine, and different aromatic bases NN = 2,2'-bipyridine [Fe(L)(bipy)]PF6 (1), 1,10-phenanthroline [Fe(L)(phen)]PF6 (2), or a phenanthroline derivative co-ligand: [Fe(L)(amphen)]NO3 (3), [Fe(L)(amphen)]PF6 (3a), [Fe(L)(Clphen)]PF6 (4), [Fe(L)(epoxyphen)]PF6 (5) (where amphen = 1,10-phenanthroline-5-amine, epoxyphen = 5,6-epoxy-5,6-dihydro-1,10-phenanthroline, Clphen = 5-chloro-1,10-phenanthroline) and the [Fe(L)(EtOH)]NO3 (6) complex are synthesized. The compounds are characterized in the solid state and in solution by elemental analysis, ESI-MS, magnetic susceptibility measurements and FTIR, UV-Vis, 1H and 13C NMR and fluorescence spectroscopies. [Fe(phen)Cl3] and [Fe(amphen)Cl3] were also prepared for comparison purposes. Spectroscopic binding studies indicate groove binding as the main interaction for most complexes with DNA, and for those containing amphen a B- to Z-DNA conformational change is proposed to occur. As determined via MTT analysis all compounds 1-6 are cytotoxic against a panel of three different cell lines (HeLa, H1299, MDA-MB-231). For selected compounds with promising cytotoxic activity, apoptosis was evaluated using cell and DNA morphology, TUNEL, Annexin V/7AAD staining and caspase3/7 activity. The compounds induce oxidative DNA damage on plasmid DNA and in cell culture as assessed by 8-oxo-Guanine and γH2AX staining. Comet assay confirmed the presence of genomic damage. There is also increased reactive oxygen species formation following drug treatment, which may be the relevant mechanism of action, thus differing from that normally assumed for cisplatin. The Fe(III)-complexes were also tested against strains of M. Tuberculosis (MTb), complex 2 depicting higher anti-MTb activity than several known second line drugs. Hence, these initial studies show prospective anti-cancer and anti-MTb activity granting promise for further studies.

Evaluation of the binding of four anti-tumor Casiopeínas® to human serum albumin.

The metal complexes designated by Casiopeínas® are mixed-ligand CuII-compounds some of them having promising antineoplastic properties. We report studies of binding of Cu(glycinato)(4,7-dimethyl-1,10-phenanthroline) (Cas-II-Gly (1)), Cu(acetylacetonato)(4,7-dimethyl-1,10-phenanthroline) (Cas-III-Ea (2)), Cu(glycinato)(4,4'-dimethyl-2,2'-bipyridine) (Cas-IV-Gly (3)) and Cu(acetylacetonato)(4,4'-dimethyl-2,2'-bipyridine) (Cas-III-ia (4)) to human serum albumin (HSA) by circular dichroism (CD), Electron paramagnetic resonance (EPR) and fluorescence spectroscopy. The results indicate that HSA may bind up to three molecules of the tested Casiopeínas. This is confirmed by inductively coupled plasma - atomic absorption spectroscopy measurements of samples of HSA-Casiopeínas after passing by adequate size-exclusion columns. The binding of Cas-II-Gly to HSA was also confirmed by MALDI-TOF mass spectrometric experiments. In the physiological range of concentrations the Casiopeínas form 1:1 adducts with HSA, with conditional binding constants of ca. 1×109 (1), 4×107 (2), 1×106 (3) and 2×105 (4), values determined from the CD spectra measured, and the fluorescence emission spectra indicates that the binding takes place close to the Trp214 residue. Overall, the data confirm that these Casiopeínas may bind to HSA and may be transported in blood serum by this protein; this might allow some selective tumor targeting, particularly in the case of Cas-II-Gly. In this work we also discuss aspects associated to the reliability of the frequently used methodologies to determine binding constants based on the measurement of fluorescence emission spectra of solutions containing low concentrations of proteins such as HSA and BSA, by titrations with solutions of metal complexes.

Studies on the mechanism of action of antitumor bis(aminophenolate) ruthenium(III) complexes.

Two recently published Ru(III) complexes bearing (N2O2) tetradentate bis(aminophenolate) ligands, formulated as [Ru(III)(salan)(PPh3)Cl] (salan is the tetradentate ligand 6,6'-(1S,2S)-cyclohexane-1,2-diylbis(azanediyl)bis(methylene)bis(3-methoxyphenol) in complex 1, or 2,2'-(1S,2S)-cyclohexane-1,2-diylbis(azanediyl)bis(methylene)bis(4-methoxyphenol) in complex 2; PPh3 is triphenylphosphane) and found very active against ovarian and breast adenocarcinoma human cells were studied to outline their antitumor mode of action. The human cisplatin-sensitive ovarian adenocarcinoma line A2780 was used herein as the cell model. At a 24h challenge (similarly as found before for 72h) both complexes are active, their cytotoxicity being comparable to that of cisplatin in the same conditions. As a possible target in the cell for their action, the interaction of 1 and 2 with DNA was assessed through displacement of well-established DNA fluorescent probes (ethidium bromide, EB, and 4',6-diamidino-2-phenylindole, DAPI) through steady-state and time-resolved fluorescence spectroscopy. The whole emission spectra were analyzed globally for the binary DNA-probe and ternary DNA-probe-Ru(III) complex systems. Both Ru(III) complexes can displace EB and bind to DNA with similar and moderate strong affinity with conditional stability constants of logK'=(5.05±0.01) for 1 and logK'=(4.79±0.01) for 2. The analysis of time-domain fluorescence intensity decays confirmed both qualitatively and quantitatively the model used to describe the binding and competition processes. Cell studies indicated that apoptosis is the major mechanism of cell death for both complexes, with 2 (the more active complex) promoting that process more efficiently than 1. Transmission electron micrographs revealed clear alterations on intracellular organization consistent with the induction of programmed cell death processes.

Vanadium(IV) and copper(II) complexes of salicylaldimines and aromatic heterocycles: Cytotoxicity, DNA binding and DNA cleavage properties.

Five copper(II) complexes, [Cu(sal-Gly)(bipy)](1), [Cu(sal-Gly)(phen)] (2), [Cu(sal-l-Ala)(phen)] (3), [Cu(sal-D-Ala)(phen)] (4), [Cu(sal-l-Phe)(phen)] (5) and five oxidovanadium(IV) complexes, [V(IV)O(sal-Gly)(bipy)] (6), [V(IV)O(sal-Gly)(phen)] (7), [V(IV)O(sal-l-Phe)(H2O)] (8), [V(IV)O(sal-l-Phe)(bipy)] (9), [V(IV)O(sal-l-Phe)(phen)] (10) (sal=salicylaldehyde, bipy=2,2'-bipyridine, phen=1,10-phenanthroline) were synthesized and characterized, and their interaction with DNA was evaluated by different techniques: gel electrophoresis, fluorescence, UV-visible and circular dichroism spectroscopy. The complexes interact with calf-thymus DNA and efficiently cleave plasmid DNA in the absence (only 2 and 5) and/or presence of additives. The cleavage ability is concentration-dependent as well as metal and ligand-dependent. Moreover, DNA binding experiments show that the phen-containing Cu(II) and V(IV)O compounds display stronger DNA interaction ability than the corresponding bipy analogues. The complexes present cytotoxic activity against human ovarian (A2780) and breast (MCF7) carcinoma cells. Cell-growth inhibition (IC50) of compounds 1, 2 and 5 in human promyelocytic leukemia (HL60) and human cervical cancer (HeLa) cells were also determined. The copper complexes show much higher cytotoxic activity than the corresponding vanadium complexes and the reference drug cisplatin (except for the sal-Gly complexes); namely, the phenanthroline copper complexes 2-5 are ca. 10-fold more cytotoxic than cisplatin and more cytotoxic than their bipyridine analogues.

Important cytotoxicity of novel iron(II) cyclopentadienyl complexes with imidazole based ligands.

Four new compounds of general formula [FeCp(dppe)L][CF3SO3] with L=imidazole substituted ligands, and dppe=ethylenebis(diphenylphosphane) have been synthesized and characterized with the aim to evaluate their anticancer properties. The new compounds were fully characterized by spectroscopic and electrochemical methods and the structure of [Fe(η(5)-C5H5)(dppe)(1-BuIm)] [CF3SO3] (1), [Fe(η(5)-C5H5)(dppe) (ImH)][CF3SO3] (3) and [Fe(η(5)-C5H5)(dppe)(1HmIm)][CF3SO3] (4) (where 1-BuIm=1-butylimidazole, and 1HmIm=N-hydroxymethylimidazole) was determined by X-ray diffraction studies. Apparently, these compounds are the first reported 'Fe(η(5)-C5H5)' half sandwich derivatives presenting high cytotoxic activity against a set a human tumor cell lines predicting their potential value as antitumor drugs.

Screening organometallic binuclear thiosemicarbazone ruthenium complexes as potential anti-tumour agents: cytotoxic activity and human serum albumin binding mechanism.

Four complexes combining the {Ru(p-cym)} moiety (p-cym = para-cymene) with thiosemicarbazone (TSC) ligands containing the 5-nitrofuryl pharmacophore were investigated in vitro for their properties as prospective anti-tumour agents. The compounds are dimeric structures of general formula [Ru2(p-cym)2(L)2]X2 where X = Cl(-), PF6(-) and L = deprotonated 5-nitrofuraldehyde TSC (L1), and the N-methyl (L2), N-ethyl (L3) and N-phenyl (L4) derivatives. The precursor [RuCl2(p-cym)]2, all TSC ligands L1-L4and their corresponding complexes 1-4 were screened in vitro for their cytotoxicity against a range of human cancer cell lines (HL-60 acute promyelocytic leukemia, A2780 ovarian adenocarcinoma, MCF7 breast adenocarcinoma and PC3 grade IV prostate carcinoma). While the precursor complex was found to be inactive and L4 exhibited moderate activity only in the MCF7 cell line, the coordination of L4 to the {Ru(p-cym)} moiety remarkably enhanced the activity of the whole complex. In fact, complex 4 [Ru2(p-cym)2(L4)2]Cl2 was found to be the most active agent of the whole series, and was studied further (as well as complex 1 for comparison). Concerning the mode of action, the mechanism of cell death for both 1 and 4 seemed to be related to apoptotic processes, and they strongly interacted with tubulin (involved in the cell cycle) and with integrin (involved in the cytoskeleton formation). As an approach to their pharmacokinetics, the interaction of 1 and 4 with human serum albumin (HSA) was assessed. A quantitative model for the binding of 4 to HSA is proposed from Circular Dichroism data, and validated by fluorescence results. Models of Förster resonance energy transfer and fluorescence quenching afforded the distance of 4 to the lone Trp214 residue. Importantly, HSA binding enhanced the cytotoxicity of 4 and correlated well with the HSA binding data. Our results consistently indicate that [Ru2(p-cymene)2(L4)2]Cl2 is quite promising as a prospective metallodrug for cancer chemotherapy.