A Multipurpose Metallophore and Its Copper Complexes with Diverse Catalytic Antioxidant Properties to Deal with Metal and Oxidative Stress Disorders: A Combined Experimental, Theoretical, and In Vitro Study.

We report the discovery that the molecule 1-(pyridin-2-ylmethylamino)propan-2-ol (HL) can reduce oxidative stress in neuronal C6 glioma cells exposed to reactive oxygen species (O2-•, H2O2, and •OH) and metal (Cu+) stress conditions. Furthermore, its association with Cu2+ generates [Cu(HL)Cl2] (1) and [Cu(HL)2](ClO4)2 (2) complexes that also exhibit antioxidant properties. Potentiometric titration data show that HL can coordinate to Cu2+ in 1:1 and 1:2 Cu2+:ligand ratios, which was confirmed by monocrystal X-ray studies. The subsequent ultraviolet-visible, electrospray ionization mass spectrometry, and electron paramagnetic resonance experiments show that they can decompose a variety of reactive oxygen species (ROS). Kinetic studies revealed that 1 and 2 mimic the superoxide dismutase and catalase activities. Complex 1 promotes the fastest decomposition of H2O2 (kobs = 2.32 × 107 M-1 s-1), efficiently dismutases the superoxide anion (kcat = 3.08 × 107 M-1 s-1), and scavenges the hydroxyl radical (RSA50 = 25.7 × 10-6 M). Density functional theory calculations support the formation of dinuclear Cu-peroxide and mononuclear Cu-superoxide species in the reactions of [Cu(HL)Cl2] with H2O2 and O2•-, respectively. Furthermore, both 1 and 2 also reduce the oxidative stress of neuronal glioma C6 cells exposed to different ROS, including O2•- and •OH.

Anti-Acanthamoeba metallopharmaceuticals: Amoebicidal activity and synergistic effect of copper(II) coordination compound.

Acanthamoeba spp. emerged as a clinically important pathogen related to amoebic keratitis. It is among the main causes of corneal transplantation and vision loss in ophthalmology. The treatment protocols have a low cure rate, high toxicity, and need for drug combination. Transition metal compounds have shown promising antiprotozoal effects. This study evaluates the amoebicidal activity of copper(II) coordination compounds in combination with chlorhexidine and the cytotoxicity to topical ocular application. These copper(II) coordination compounds were screened against Acanthamoeba castellanii trophozoites (ATCC 50492). The cytotoxicity on rabbit corneal cell line (ATCC-CCL 60) was performed. The compounds showed high amoebicidal potential, with inhibition of trophozoite viability above 80%. The Cp12 and Cp13 compounds showed Minimal Inhibitory Amoebicidal Concentration (MIAC) at 200 µM and mean inhibitory concentration (IC50) values lower than 10 µM. Against the cysts, Cp12 showed a reduction in viability (48%) in the longest incubation period. A synergistic effect for Cp12 with chlorhexidine was observed. The compounds have a dose-dependent effect against rabbit corneal cells. Compound Cp12 has potential for future application in developing ophthalmic formulations against Acanthamoeba keratitis and its use in multipurpose solutions is highlighted.

Exploring the antioxidant activity of Fe(III), Mn(III)Mn(II), and Cu(II) compounds in Saccharomyces cerevisiae and Galleria mellonella models of study.

Reactive oxygen species (ROS) are closely related to oxidative stress, aging, and the onset of human diseases. To mitigate ROS-induced damages, extensive research has focused on examining the antioxidative attributes of various synthetic/natural substances. Coordination compounds serving as synthetic antioxidants have emerged as a promising approach to attenuate ROS toxicity. Herein, we investigated the antioxidant potential of a series of Fe(III) (1), Mn(III)Mn(II) (2) and Cu(II) (3) coordination compounds synthesized with the ligand N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)[(3-chloro)(2-hydroxy)]-propylamine in Saccharomyces cerevisiae exposed to oxidative stress. We also assessed the antioxidant potential of these complexes in the alternative model of study, Galleria mellonella. DPPH analysis indicated that these complexes presented moderate antioxidant activity. However, treating Saccharomyces cerevisiae with 1, 2 and 3 increased the tolerance against oxidative stress and extended yeast lifespan. The treatment of yeast cells with these complexes decreased lipid peroxidation and catalase activity in stressed cells, whilst no change in SOD activity was observed. Moreover, these complexes induced the Hsp104 expression. In G. mellonella, complex administration extended larval survival under H2O2 stress and did not affect the insect's life cycle. Our results suggest that the antioxidant potential exhibited by these complexes could be further explored to mitigate various oxidative stress-related disorders.

In vitro anti-Leishmania activity of new isomeric cobalt(II)complexes and in silico insights: Mitochondria impairment and apoptosis-like cell death of the parasite.

The synthesis, physico-chemical characterization and in vitro antiproliferative activity against the promastigote form of Leishmania amazonensis of two new cobalt(II) coordination compounds (i.e. [Co(HL1)Cl2]0.4,2H2O (1) and [Co(HL2)(Cl)(CH3OH)](ClO4).2H2O (2)) are reported, where HL1 = 4-{3-[bis(pyridin-2-ylmethyl)amino]-2-hydroxypropoxy}-2H-chromen-2-one and HL2 = 7-{3-[bis(pyridin-2-ylmethyl)amino]-2-hydroxypropoxy}-2H-chromen-2-one. X-ray diffraction studies were performed for complex (2) and the structure of complex (1) was built through Density Functional Theory (DFT) calculations. Complex (1) presented no cytotoxicity to LLC-MK2, but complex (2) was toxic. IC50 against promastigotes of L. amazonensis for complex (1) were 4.90 (24 h), 3.50 (48 h) and 3. 80 µmol L-1 (72 h), and for complex (2) were 2.09, 4.20 and 2.80 µmol L-1, respectively. Due to the high toxicity presented by complex (2) against LLC-MK2 host cells, mechanistic studies, to shed light on the probable mode of leishmanicidal activity, were carried out only for the non-cytotoxic complex. Complex (1) was able to elevate mitochondrial membrane potential of the parasites after treatment. Transmission electron microscopy revealed typical apoptotic condensation of chromatin, altered kinetoplast and mitochondria structures, suggesting that apoptosis-like cell death of the protozoa is probably mediated by an apoptotic mechanism associated with mitochondrial dysfunction (intrinsic pathway). Molecular docking studies with complex (1) upon protein tyrosine phosphatase (LmPRL-1) suggests a plausible positive complex anchoring mainly by hydrophobic and hydrogen bond forces close to the enzyme's catalytic site. These promising results for complex 1 will prompt future investigations against amastigote form of L. amazonensis.

ROS scavenging of SOD/CAT mimics probed by EPR and reduction of lipid peroxidation in S. cerevisiae and mouse liver, under severe hydroxyl radical stress condition.

The interaction between CuII, FeIII and MnII complexes, derived from the ligands 1-[bis(pyridine-2-ylmethyl)amino]-3-chloropropan-2-ol (hpclnol) and bis(pyridine-2-ylmethyl)amine (bpma), and the free radical 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl (DPPH) and reactive oxygen species (ROS), was investigated by colorimetric and EPR (Electron Paramagnetic Resonance) techniques. A comparison between these results and those reported to [Mn(salen)Cl] or EUK-8 was also addressed. EPR studies allowed us the identification of intermediates species such as superoxide­copper(I) and superoxide­copper(II), a mixed-valence FeIIIFeII species and a 16-line feature attributed to MnIII-oxo-MnIV species. The biomarker malondialdehyde (MDA) was determined by TBARS assay in S. cerevisiae cells, and the determination of the IC50 indicate that the antioxidant activity shown dependence on the metal center (CuII ≈ FeIII > MnII ≈ [Mn(salen)Cl]. The lipid peroxidation attenuation was also investigated in liver homogenates obtained from Swiss mice and the IC50 values were in the nanomolar concentrations. We demonstrated here that all the complexes interact with the free radical DPPH and with ROS (H2O2, O2•- and hydroxyl radical), enhancing the cellular protection against oxidative stress generated by hydroxyl radical, employing two experimental model systems, S. cerevisiae (in vivo) and mouse liver (ex vivo).

Scavenging of reactive species probed by EPR and ex-vivo nanomolar reduction of lipid peroxidation of manganese complexes.

Antioxidant activity toward H2O2, anion radical superoxide, hydroxyl and DPPH (2,2-diphenyl-1-picrylhydrazyl) of two manganese complexes [Mn(III)(bpa)2]Cl.H2O (1) and [(Cl)Mn(µ-hbpclnol)(µ-bpclnol)Mn](ClO4).3H2O (2) (hbpa = (2-hydroxybenzyl-2-pyridylmethyl)amine and h2bpclnol = (N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)[(3-chloro)(2-hydroxy)]propylamine) are presented. X-ray diffraction studies were performed for complex (1). Both complexes presented similar or better activities than reference complex [Mn(salen)Cl], when the interaction between them and ROS (H2O2, O2•- and •OH), was monitored, by EPR (Electron Paramagnetic Resonance), in PBS, DMSO and water. The antioxidant activity rank of complexes toward •OH, generated by Fenton reaction and monitored by EPR, is (2) > (1) > [Mn(salen)Cl], in water (0.1% of DMSO for each complex), with the values of the IC50 of 7.2 (±1.6), 15.5 (±1.8) and 29.1 (±2.01) µM respectively. EPR data presented herein suggest that complex (2) presents the better scavenging activity toward hydroxyl, being in good agreement with TBARS assay results, in which complex (2) presented the best inhibitory activity toward lipid peroxidation, employing Swiss mice liver homogenate tissue model. IC50 values obtained from the interaction between these complexes and hydroxyl, using TBARS method, were: 0.88 (± 0.029); 0.73 (± 0.01) and 42.7 (± 3.5) nM, respectively for (1), (2) and [Mn(salen)Cl]. Complexes (1) and (2) are regulating the lipid homeostasis, protecting the tissue from the lipid peroxidation, in nanomolar scale, motivating in vivo studies. Redox properties and radical scavenging activity of complexes toward DPPH are non-linear and solvent dependent. Furthermore, the monitoring of antioxidant activity probed by EPR could be a fair and appropriate study to guide more advanced investigations.

Synthesis, characterization and computational investigation of the phosphatase activity of a dinuclear Zinc(II) complex containing a new heptadentate asymmetric ligand.

We report the synthesis of a new asymmetric heptadentate ligand based on the 1,3-diaminopropan-2-ol backbone. The ligand 3-[[3-(bis-pyridin-2-ylmethyl-amino)-2-hydroxy-propyl]-(2-carbamoyl-ethyl)-amino]-propionamide (HL1) contains two amide and two pyridine groups attached to the 1,3-diaminopropan-2-ol core. Reaction between HL1 and Zn(ClO4)2.6H2O resulted in the formation of the dinuclear [Zn2(L1)(µ-OAc)](ClO4)2 complex, characterized by single crystal X-ray diffraction, 1H, 13C and 15N NMR, ESI-(+)-MS, CHN elemental analysis as well as infrared spectroscopy. The phosphatase activity of the complex was studied in the pH range 6-11 employing pyridinium bis(2,4-dinitrophenyl)phosphate (py(BDNPP)) as substrate. The complex exhibited activity dependent on the pH, presenting an asymmetric bell shape profile with the highest activity at pH 9; at high pH ligand exchange is rate-limiting. The hydrolysis of BDNPP- at pH 9 displayed behavior characteristic of Michaelis-Menten kinetics, with kcat = 5.06 × 10-3 min-1 and Km = 5.7 ± 1.0 mM. DFT calculations map out plausible reaction pathways and identify a terminal, Zn(II)-bound hydroxide as likely nucleophile.

In Vitro and In Vivo Relevant Antineoplastic Activity of Platinum(II) Complexes toward Triple-Negative MDA-MB-231 Breast Cancer Cell Line.

Two platinum complexes [Pt(HL3)Cl]·H2O (3) and [Pt(HL4)Cl]·H2O (4) containing α- and ß-naphthyl groups, respectively, were investigated in more detail in vitro and in vivo for antineoplastic activity. The cytotoxicity activity induced by these platinum(II) compounds against breast cancer (MDA-MB-231 and MCF-7), lung (A549), prostate (PC3), pancreas (BXPC-3), and normal peripheral blood mononuclear (PBMC) cells were evaluated by MTT assay. The cell viability MTT assay showed that complex (4) was more cytotoxic to all cancer cell lines tested and less cytotoxic against human PBMC. Therefore, complex (4) was selected to further investigate the mechanism of cytotoxic effects involved against MDA-MB-231 cell line (human triple-negative breast cancer). Sub-G1 analysis of the cell cycle showed that this complex induces cell death by apoptosis due to the cell loss of DNA content detected in flow cytometry. The cytotoxic effect induced by complex (4) was associated with the capability of the complex to induce mitochondrial membrane depolarization, as well as increase ROS levels and caspase activation, as a result of the activation of both extrinsic and intrinsic apoptosis pathways. Ultrastructural alterations were observed using scanning and transmission electron microscopy (SEM and TEM), such as membrane blebbing, filopodia reduction, empty mitochondrial matrix, and DNA fragmentation. Furthermore, complex (4) was tested in an MDA-MB-231 tumor nodule xenograft murine model and demonstrated a remarkable reduction in tumor size in BALB/c nude mice, when compared to the control animals.

Development of new dinuclear Fe(III) coordination compounds with in vitro nanomolar antitrypanosomal activity.

Chagas disease is a neglected tropical disease caused by the protozoan pathogen Trypanosoma cruzi. The disease is a major public health problem affecting about 6 to 7 million people worldwide, mostly in Latin America. The available therapy for this disease is based on two drugs, nifurtimox and benznidazole, which exhibit severe side effects, including resistance, severe cytotoxicity, variable efficacy and inefficiency in the chronic phase. Therefore, new drugs are urgently needed. Coordination compounds may be an interesting alternative for antiparasite therapy against Leishmania spp., Toxoplasma gondii and T. cruzi. Herein, we tested the in vitro effect on T. cruzi epimastigotes (Y strain) of two new µ-oxo Fe(III) dinuclear complexes: [(HL1)(Cl)Fe(µ-O)Fe(Cl)(HL2)](Cl)2·(CH3CH2OH)2·H2O (1) and [(HL2)(Cl)Fe(µ-O)Fe(Cl)(HL2)](Cl)2·H2O (2) where HL1 and HL2 are ligands which contain two pyridines, amine and alcohol moieties with a naphthyl pendant unit yielding a N3O coordination environment. Complexes (1) and (2), which are isomers, were completely characterized, including X-ray diffraction studies for complex (1). Parasites were treated with the complexes and the outcome was analyzed. Complex (1) exhibited the lowest IC50 values, which were 99 ± 3, 97 ± 2 and 110 ± 39 nM, after 48, 72 and 120 h of treatment, respectively. Complex (2) showed IC50 values of 118 ± 5, 122 ± 6 and 104 ± 29 nM for the same treatment times. Low cytotoxicity to the host cell LLC-MK2 was found for both complexes, resulting in impressive selectivity indexes of 106 for complex (1) and 178 for (2), after 120 h of treatment. Treatment with both complexes reduced the mitochondrial membrane potential of the parasite. Ultrastructural analysis of the parasite after treatment with complexes showed that the mitochondria outer membrane presented swelling and abnormal disposition around the kinetoplast; in addition, reservosomes presented anomalous spicules and rupture. The complexes showed low nanomolar IC50 values affecting mitochondria and reservosomes, essential organelles for the survival of the parasite. The low IC50 and the high selectivity index show that both complexes act as a new prototype of drugs against T. cruzi and may be used for further development in drug discovery to treat Chagas disease.

Antitumor activity via apoptotic cell death pathway of water soluble copper(II) complexes: effect of the diamino unit on selectivity against lung cancer NCI-H460 cell line.

The cytotoxicity against five human tumor cell lines (THP-1, U937, Molt-4, Colo-205 and NCI-H460) of three water soluble copper(II) coordination compounds containing the ligands 3,3'-(ethane-1,2-diylbis(azanediyl))dipropanamide (BCEN), 3,3'-(piperazine-1,4-diyl)dipropanamide (BPAP) or 3,3'-and (1,4-diazepane-1,4-diyl)dipropanamide (BPAH) are reported in this work. The ligands contain different diamine units (ethylenediamine, piperazine or homopiperazine) and two propanamide units attached to the diamine centers, resulting in N2O2 donor sets. The complex containing homopiperazine unit presented the best antiproliferative effect and selectivity against lung cancer cell line NCI-H460, showing inhibitory concentration (IC50) of 58 µmol dm-3 and Selectivity Index (SI) > 3.4. The mechanism of cell death promoted by the complex was investigated by Sub-G1 cell population analysis and annexin V and propidium iodide (PI) labeling techniques, suggesting that the complex promotes death by apoptosis. Transmission electron microscopy investigations are in agreement with the results presented by mitochondrial membrane potential analysis and also show the impairment of other organelles, including endoplasmic reticulum.

Effect of the hydroxamate group in the antitumoral activity and toxicity toward normal cells of new copper(II) complexes.

The synthesis, physico-chemical characterization and cytotoxicity of four copper(II) coordination complexes, i.e. [Cu(HBPA)Cl2] (1), [Cu(BHA)2] (2), [Cu(HBPA)(BHA)Cl] CH3OH (3) and [Cu(HBPA)2]Cl2·4H2O (4), are reported. HBPA is the tridentate ligand N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)amine and HBHA is the benzohydroxamic acid. The reaction between the HBHA and CuCl2.2H2O has resulted in the new complex (2) and the reaction between complex (1) and HBHA has resulted in the new complex (3). X-ray diffraction studies for complex (3) indicated the effective coordination of HBHA as BHA-. Their cytotoxicity was evaluated against three human tumoral cell lines (Colo-205, NCI-H460 and U937) and PBMC (peripheral blood mononuclear cells), using the MTT cytotoxic assay. The results toward PBMC reveal that the new copper(II) complex (2) presents lower toxicity toward normal cells. Furthermore, complex (2) presents IC50 values lower than cisplatin toward NCI-H460 and the best selectivity index obtained towards NCI-H460 (SI = 2.2) and U937 cell lines (SI = 2.0), as a result of the presence of two molecules of HBHA in its structure. Complex (3) presents IC50 values lower than cisplatin toward NCI-H460, Colo-205 and comparable to cisplatin toward U937. The evaluation of the cell death type promoted by complexes (2) and (4) was investigated toward NCI-H460 revealing better results than the standard drug cisplatin, according to the Annexin V and propidium iodide (PI) labeling experiment. Based on the studies here performed, HBHA seems to be related to lower toxicity toward PBMC and HBPA is improving directly the cytotoxity.

Recent Advances in Heterogeneous Catalytic Systems Containing Metal Ions for Phosphate Ester Hydrolysis.

Organophosphates are a class of organic compounds that are important for living organisms, forming the building blocks for DNA, RNA, and some essential cofactors. Furthermore, non-natural organophosphates are widely used in industrial applications, including as pesticides; in laundry detergents; and, unfortunately, as chemical weapons agents. In some cases, the natural degradation of organophosphates can take thousands of years; this longevity creates problems associated with handling and the storage of waste generated by such phosphate esters, in particular. Efforts to develop new catalysts for the cleavage of phosphate esters have progressed in recent decades, mainly in the area of homogeneous catalysis. In contrast, the development of heterogeneous catalysts for the hydrolysis of organophosphates has not been as prominent. Herein, examples of heterogeneous systems are described and the importance of the development of heterogeneous catalysts applicable to organophosphate hydrolysis is highlighted, shedding light on recent advances related to different solid matrices that have been employed.

In vitro and in vivo anti-proliferative activity and ultrastructure investigations of a copper(II) complex toward human lung cancer cell NCI-H460.

The aim of our study was to evaluate the in vitro and in vivo anti-proliferative potential of complex (2) [Cu (L1)Cl]Cl.2H2O, where L1 = 1-[2-hydroxybenzyl(2-pyridylmethyl)amino]-3-(1-naphthyloxy)-2-propanol on lung carcinoma cell NCI-H460. Cell viability assay determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric assay demonstrated that the complex (2) exhibits higher activity against the NCI-H460 cell, with an IC50 value lower than cisplatin (26.5 µM ± 1.1 and 203 ± 1.2 µM respectively). Cell death by apoptosis was investigated by flow cytometer analysis of sub-G1 populations in the cell cycle and Annexin V/Propidium Iodide assay. Changes on the cell surface and ultrastructure were detected by scanning and transmission electron microscopy. Our work revealed that complex (2) induced changes associated with apoptosis, such as plasma membrane blebbing and a lower microvilli amount, fragmentation and condensation of chromatin, alterations in mitochondria, and enlargement of the endoplasmic reticulum. Mitochondrial function of NCI-H460 cells evaluated by 5,5',6,6'-tetrachloro 1,1',3,3' tetraethylbenzimidazolylcarbocyanine iodide (JC-1) probes showed high loss of mitochondrial membrane potential when treated with complex (2). Moreover, caspase-12 measurement showed an expressive activation level, which is related to endoplasmic reticulum stress. In vivo assay using the murine model of human lung cancer cell showed that complex (2) and cisplatin has similar antineoplastic activity.

Iron and copper complexes with antioxidant activity as inhibitors of the metastatic potential of glioma cells.

Gliomas are the most common type of primary brain tumors, presenting high mortality and recurrence rates that highlight the need for the development of more efficient therapies. In that context, we investigated iron(iii) (FeL) and copper(ii) (CuL) complexes containing the tetradentate ligand 2-{[(3-chloro-2-hydroxy-propyl)-pyridin-2-ylmethyl-amino]-methyl}-phenol (L) as potential antimetastatic compounds in glioma cells. These complexes were designed to act as mimetics of antioxidant metalloenzymes (catalases and superoxide dismutase) and thus interfere with the production of reactive oxygen species (ROS), important signaling molecules that have been linked to the induction of Epithelial-Mesenchymal Transition (EMT) in cancer cells, a process associated with cancer invasion and aggressiveness. The results obtained have revealed that, in vitro, both compounds act as superoxide dismutase or catalase mimetics, and this translated in glioma cells into a decrease in ROS levels in FeL-treated cells. In addition, both complexes were found to inhibit the migration of monolayer-grown H4 cells and lead to decreased expression of EMT markers. More importantly, this behavior was recapitulated in 3D spheroids models, where CuL in particular was found to completely inhibit the invasion ability of glioma cells, with or without cellular irradiation with X-rays, which is suggestive of these compounds' potential to be used in combination with radiotherapy. Overall, the results herein obtained describe the novel use of these complexes as agents that are able to interfere with regulation of EMT and the invasive behavior of glioma cells, an application that deserves to be further explored.

Modulating the antitumoral activity by the design of new platinum(II) compounds: Synthesis, characterization, DFT, ultrastructure and mechanistic studies.

The synthesis, physico-chemical characterization, Density functional theory (DFT) calculation and cytotoxicity against five human tumoral cell lines (THP-1, U937, Molt-4, Colo205 and H460) of four new platinum(II) coordination compounds are reported, i.e. [Pt(HL1)Cl]·H2O (1), [Pt(HL2)Cl]·H2O (2), [Pt(HL3)Cl]·H2O (3) and [Pt(HL4)Cl]·H2O (4). The ligands contain N2O donor sets. Furthermore, H2L3 and H2L4 present α and ß-naphthyl groups respectively, which are absent in HL1 and H2L2. X-ray diffraction studies were performed for complex (3), indicating the formation of a mononuclear platinum(II) complex. Complexes (3) and (4), which contain α and ß-naphthyl groups respectively, have presented lower IC50 (inhibitory concentration) values than those exhibited by complexes (1) and (2). The mechanism of cell death promoted by complexes (3) and (4) was investigated, suggesting that, toward U937 cell line, the α isomer promotes death by apoptosis and the ß isomer by necrosis. Transmission and scanning electron microscopy investigations are in agreement with the loss of mitochondrial membrane potential (ΔΨm) observed by JC-1 mitochondrial potential sensor and indicate that the activity of complex (3) against U937 cell line is mediated by an apoptotic mechanism associated with mitochondrial dysfunction. A quantification of caspases 3, 6, 8 and 9 indicated that both the intrinsic and extrinsic pathways are involved in the apoptotic stimuli. Based on DFT calculations all the Pt(II) complexes present the same coordination environment for the metal centre, indicating that the higher cytotoxic activities exhibited by complexes (3) and (4) are related to the presence of the α and ß-naphthyl groups in the ligand structure.

A New Mixed-Valence Mn(II)Mn(III) Compound With Catalase and Superoxide Dismutase Activities.

The synthesis, X-ray molecular structure, physico-chemical characterization and dual antioxidant activity (catalase and superoxide dismutase) of a new polymeric mixed valence Mn(III)Mn(II) complex, containing the ligand H2BPClNOL (N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)[(3-chloro)(2-hydroxy)] propylamine) is described. The monomeric unit is composed of a dinuclear Mn(II)Mn(III) moiety, [Mn(III)(µ-HBPClNOL)(µ-BPClNOL)Mn(II)(Cl)](ClO4)·2H2O, 1, in which the Mn ions are connected by two different bridging groups provided by two molecules of the ligand H2BPClNOL, a phenoxide and an alkoxide group. In the solid state, this mixed valence dinuclear unit is connected to its neighbors through chloro bridges. Magnetic measurements indicated the presence of ferromagnetic [J = +0.076(13) cm-1] and antiferromagnetic [J = -5.224(13) cm-1] interactions. The compound promotes O 2 • - dismutation in aqueous solution (IC50 = 0.370 µmol dm-3, k cat = 3.6x106 M-1 s-1). EPR studies revealed that a high-valent Mn(III)-O-Mn(IV) species is involved in the superoxide dismutation catalytic cycle. Complex 1 shows catalase activity only in the presence of a base, e.g., piperazine or triethylamine. Kinetic studies were carried out in the presence of piperazine and employing two different methods, resulting in k cat values of 0.58 ± 0.03 s-1 (detection of O2 production employing a Clark electrode) and 2.59 ± 0.12 s-1 (H2O2 consuption recorded via UV-Vis). EPR and ESI-(+)-MS studies indicate that piperazine induces the oxidation of 1, resulting in the formation of the catalytically active Mn(III)-O-Mn(IV) species.

A new iron(III) complex-containing sulfadiazine inhibits the proliferation and induces cystogenesis of Toxoplasma gondii.

We have previously shown that metallocomplexes can control the growth of Toxoplasma gondii, the agent that causes toxoplasmosis. In order to develop new metallodrugs to treat this disease, we investigated the influence of the coordination of sulfadiazine (SDZ), a drug used to treat toxoplasmosis, on the biological activity of the iron(III) complex [Fe(HBPClNOL)Cl2]·H2O, 1, (H2BPClNOL=N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)(3-chloro)(2-hydroxy)-propylamine). The new complex [(Cl)(SDZ)Fe(III)(µ-BPClNOL)2Fe(III)(SDZ)(Cl)]·2H2O, 2, which was obtained by the reaction between complex 1 and SDZ, was characterized using a range of physico-chemical techniques. The cytotoxic effect of the complexes and the ability of T. gondii to infect LLC-MK2 cells were assessed. It was found that both complexes reduced the growth of T. gondii while also causing low cytotoxicity in the host cells. After 48 h of treatment, complex 2 reduced the parasite's ability to proliferate by about 50% with an IC50 of 1.66 µmol/L. Meanwhile, complex 1 or SDZ alone caused a 40% reduction in proliferation, and SDZ displayed an IC50 of 5.3 µmol/L. In addition, complex 2 treatment induced distinct morphological and ultrastructural changes in the parasites and triggered the formation of cyst-like forms. These results show that the coordination of SDZ to the iron(III) complex is a good strategy for increasing the anti-toxoplasma activity of these compounds.

Metal-based superoxide dismutase and catalase mimics reduce oxidative stress biomarkers and extend life span of Saccharomyces cerevisiae.

Aging is a natural process characterized by several biological changes. In this context, oxidative stress appears as a key factor that leads cells and organisms to severe dysfunctions and diseases. To cope with reactive oxygen species and oxidative-related damage, there has been increased use of superoxide dismutase (SOD)/catalase (CAT) biomimetic compounds. Recently, we have shown that three metal-based compounds {[Fe(HPClNOL)Cl2]NO3, [Cu(HPClNOL)(CH3CN)](ClO4)2 and Mn(HPClNOL)(Cl)2}, harboring in vitro SOD and/or CAT activities, were critical for protection of yeast cells against oxidative stress. In this work, treating Saccharomyces cerevisiae with these SOD/CAT mimics (25.0 µM/1 h), we highlight the pivotal role of these compounds to extend the life span of yeast during chronological aging. Evaluating lipid and protein oxidation of aged cells, it becomes evident that these mimics extend the life expectancy of yeast mainly due to the reduction in oxidative stress biomarkers. In addition, the treatment of yeast cells with these mimics regulated the amounts of lipid droplet occurrence, consistent with the requirement and protection of lipids for cell integrity during aging. Concerning SOD/CAT mimics uptake, using inductively coupled plasma mass spectrometry, we add new evidence that these complexes, besides being bioabsorbed by S. cerevisiae cells, can also affect metal homeostasis. Finally, our work presents a new application for these SOD/CAT mimics, which demonstrate a great potential to be employed as antiaging agents. Taken together, these promising results prompt future studies concerning the relevance of administration of these molecules against the emerging aging-related diseases such as Parkinson's, Alzheimer's and Huntington's.

Metallohydrolase biomimetics with catalytic and structural flexibility.

The structural and functional properties of zinc(ii) complexes of two nitrogen rich polydentate ligands, HTPDP = 1,3-bis(bis-pyridin-2-ylmethylamino)propan-2-ol and HTPPNOL = N,N,N'-tris-(2-pyridylmethyl)-1,3-diaminopropan-2-ol, are compared. HTPDP is a hepta-dentate ligand with four pyridyl groups attached to a 1,3-diaminopropan-2-ol backbone while HTPPNOL contains only three pyridyl groups. In reactions with Zn(ClO4)2, HTPDP forms a dinuclear zinc compound [Zn2(TPDP)(OAc)](ClO4)2, 1. On the other hand, mononuclear [Zn(HTPPNOL)](ClO4)2, 2, and tetranuclear [Zn4(TPPNOL)2(OAc)3](ClO4)3, 3, complexes were isolated with the ligand HTPPNOL. Kinetic measurements with the substrate bis(2,4-dinitrophenyl)phosphate (BDNPP) revealed that compound 1 (kcat = 31.4 × 10-3 min-1) is more reactive than 3 (kcat = 7.7 × 10-3 min-1) at pH = 8.5, whilst the mononuclear compound 2 is inactive. Compound 1 displays a typical steady-state kinetic behaviour, while compound 3 exhibits steady-state behaviour only ∼120 s after starting the reaction, preceded by a burst-phase. 31P NMR studies confirm that 1 can promote the hydrolysis of both ester bonds in BDNPP, generating the monoester DNPP and inorganic phosphate in the process. In contrast, DNPP is not a substrate for 3. The crystal structure of the complex formed by 3 and DNPP reveals the formation of a tetranuclear zinc complex [Zn4(TPPNOL)2(DNPP)2](ClO4)2, 4, in which the phosphate moiety of DNPP adopts an unusual tridentate µ-η1:η1:η1 coordination mode.