Publications by authors named "Luiz Gonzaga de França Lopes"

27 Publications

  • Page 1 of 1

Synthesis and potential vasorelaxant effect of a novel ruthenium-based nitro complex.

J Inorg Biochem 2022 Mar 26;228:111666. Epub 2021 Nov 26.

Department of Physiology and Pharmacology, School of Medicine, Federal University of Ceará, Coronel Nunes de Melo St., 1127, 60.430-275 Fortaleza, CE, Brazil; Drug Research and Development Center (NPDM), Federal University of Ceará, Coronel Nunes de Melo St., 1000, 60.430-275 Fortaleza, CE, Brazil.

This study aimed to investigate the synthesis and potential vasodilator effect of a novel ruthenium complex, cis-[Ru(bpy)(2-MIM)(NO)]PF (bpy = 2,2'-bipyridine and 2-MIM = 2-methylimidazole) (FOR711A), containing an imidazole derivative via an in silico molecular docking model using β1 H-NOX (Heme-nitric oxide/oxygen binding) domain proteins of reduced and oxidized soluble guanylate cyclase (sGC). In addition, pharmacokinetic properties in the human organism were predicted through computational simulations and the potential for acute irritation of FOR711A was also investigated in vitro using the hen's egg chorioallantoic membrane (HET-CAM). FOR711A interacted with sites of the β1 H-NOX domain of reduced and oxidized sGC, demonstrating shorter bond distances to several residues and negative values of total energy. The predictive study revealed molar refractivity (RM): 127.65; Log Po/w = 1.29; topological polar surface area (TPSA): 86.26 Å; molar mass (MM) = 541.55 g/mol; low solubility, high unsaturation index, high gastrointestinal absorption; toxicity class 4; failure to cross the blood-brain barrier and to react with cytochrome P450 (CYP) enzymes CYP1A2, CYP2C19, CYP2C9, CYP2D6 and CYP3A4. After the HET-CAM assay, the FOR711A complex was classified as non-irritant (N.I.) and its vasodilator effect was confirmed through greater evidence of blood vessels after the administration and ending of the observation period of 5 min. These results suggest that FOR711A presented a potential stimulator/activator effect of sGC via NO/sGC/cGMP. However, results indicate it needs a vehicle for oral administration.
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http://dx.doi.org/10.1016/j.jinorgbio.2021.111666DOI Listing
March 2022

The Role of Ruthenium Compounds in Neurologic Diseases: A Minireview.

J Pharmacol Exp Ther 2022 Jan 2;380(1):47-53. Epub 2021 Nov 2.

Department of Morphology and the Institute of Biomedicine, School of Medicine (F.V.G.J., G.A.M., J.d.S.R.C., C.R.R., R.B.O.) and Department of Organic and Inorganic Chemistry (E.M.C., L.G.d.F.L.), Federal University of Ceará, Fortaleza, Brazil; Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, Louisiana (L.B.); and Laboratory of Experimental Vascular Surgery and Gene Expression, School of Medicine, Christus University Center (UNICHRISTUS), Fortaleza, Brazil (M.W.S.C.)

Ruthenium compounds, nitric oxide donors in biologic systems, have emerged as a promising therapeutic alternative to conventional drugs in anticancer chemotherapy and as a potential neuroprotective agent with fewer cytotoxic effects. This minireview summarizes promising studies with ruthenium complexes and their roles in cancer, neuroinflammation, neurovascular, and neurodegenerative diseases. The up-to-date evidence supports that ruthenium-based compounds have beneficial effects against gliomas and other types of brain cancers, reduce motor symptoms in models of cerebral ischemia-reperfusion, and may act in the control of nociceptive and inflammatory events, such as those seen in early Alzheimer's disease. More studies are needed to fill many current knowledge gaps about the intricate and complex biologic effects and therapeutic-related mechanisms of ruthenium, stimulating further research. SIGNIFICANCE STATEMENT: This minireview summarizes studies addressing the role of ruthenium compounds on neurological illnesses, focusing on brain cancer and neurovascular and neurodegenerative diseases. No such review is available in the literature.
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http://dx.doi.org/10.1124/jpet.121.000798DOI Listing
January 2022

The biofilm inhibition activity of a NO donor nanosilica with enhanced antibiotics action.

Int J Pharm 2021 Dec 20;610:121220. Epub 2021 Oct 20.

Departamento de Química Analítica e Físico-Química, Universidade Federal do Ceará, Fortaleza, CE 60440-900, Brazil. Electronic address:

Nitric oxide (NO) has emerged as a promising antibacterial agent, where NO donor compounds have been explored. Here, we investigated the role of a silica nanoparticle containing nitroprusside (MPSi-NP) as a NO donor agent against methicillin-sensitive (ATCC 25,923 and ATCC 12228) and methicillin-resistant (ATCC 700,698 and ATCC 35984) Staphylococcus strains. Biofilm inhibition was studied along with antibiotic activity in combination with standard antibiotics (ampicillin and tetracycline). MPSi-NP exhibited thermal release of 63% of NO within 24 h, while free nitroprusside released only 18% during a dialysis assay, indicating an assisted release of NO mediated by the nanoparticles. This nanomaterial showed only a moderate activity in blocking biofilm production, but exhibited a significant decrease in the number of viable bacterial cells (over 600-fold for Staphylococcus aureus ATCC 700,698 and Staphylococcus epidermidis ATCC 35984). Remarkably, even using MPSi-NP at concentrations below any antibacterial action, its combination with ampicillin promoted a significant decrease in MIC for resistant strains of S. aureus ATCC 700,698 (2-fold) and S. epidermidis ATCC 35,984 (4-fold). A carbopol-based gel formulation with MPSi-NP (0.5% w/w) was prepared and showed a zone of inhibition of 7.7 ± 0.6 mm for S. epidermidis ATCC 35984. Topical use of MPSi-NP in combination with antibiotics might be a manageable strategy to prevent and eventually treat complicated resistant bacterial infections.
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http://dx.doi.org/10.1016/j.ijpharm.2021.121220DOI Listing
December 2021

Nitric Oxide as a Central Molecule in Hypertension: Focus on the Vasorelaxant Activity of New Nitric Oxide Donors.

Biology (Basel) 2021 Oct 14;10(10). Epub 2021 Oct 14.

Laboratory of Nutrition, Physical Activity and Phenotypic Plasticity, Federal University of Pernambuco, Vitória de Santo Antão 55.608-680, PE, Brazil.

Cardiovascular diseases include all types of disorders related to the heart or blood vessels. High blood pressure is an important risk factor for cardiac complications and pathological disorders. An increase in circulating angiotensin-II is a potent stimulus for the expression of reactive oxygen species and pro-inflammatory cytokines that activate oxidative stress, perpetuating a deleterious effect in hypertension. Studies demonstrate the capacity of NO to prevent platelet or leukocyte activation and adhesion and inhibition of proliferation, as well as to modulate inflammatory or anti-inflammatory reactions and migration of vascular smooth muscle cells. However, in conditions of low availability of NO, such as during hypertension, these processes are impaired. Currently, there is great interest in the development of compounds capable of releasing NO in a modulated and stable way. Accordingly, compounds containing metal ions coupled to NO are being investigated and are widely recognized as having great relevance in the treatment of different diseases. Therefore, the exogenous administration of NO is an attractive and pharmacological alternative in the study and treatment of hypertension. The present review summarizes the role of nitric oxide in hypertension, focusing on the role of new NO donors, particularly the metal-based drugs and their protagonist activity in vascular function.
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http://dx.doi.org/10.3390/biology10101041DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8533285PMC
October 2021

Further Insights into the Oxidative Pathway of Thiocarbonyl-Type Antitubercular Prodrugs: Ethionamide, Thioacetazone, and Isoxyl.

Chem Res Toxicol 2021 08 28;34(8):1879-1889. Epub 2021 Jul 28.

CNRS, Laboratoire de Chimie de Coordination, LCC, UPR 8241, 205 Route de Narbonne, BP 44099, F-31077 Toulouse, Cedex 4, France.

A chemical activation study of the thiocarbonyl-type antitubercular prodrugs, ethionamide (ETH), thioacetazone (TAZ), and isoxyl (ISO), was performed. Biomimetic oxidation of ethionamide using HO (1 equiv) led to ETH-SO as the only stable -oxide compound, which was found to occur in solution in the preferential form of a sulfine (ETH═S═O vs the sulfenic acid tautomer ETH-S-OH), as previously observed in the crystal state. It was also demonstrated that ETH-SO is capable of reacting with amines, as the putative sulfinic derivative (ETH-SOH) was supposed to do. Unlike ETH, oxidation of TAZ did not allow observation of the mono-oxygenated species (TAZ-SO), leading directly to the more stable sulfinic acid derivative (TAZ-SOH), which can then lose a SOH group after further oxidation or when placed in a basic medium. It was also noticed that the unstable TAZ-SO intermediate can lead to the carbodiimide derivative as another electrophilic species. It is suggested that TAZ-SOH, TAZ-SOH, and the carbodiimide compound can also react with NH-containing nucleophilic species, and therefore be involved in toxic effects. Finally, ISO showed a very complex reactivity, here assigned to the coexistence of two mono-oxygenated structures, the sulfine and sulfenic acid tautomers. The mono- and dioxygenated derivatives of ISO are also highly unstable, leading to a panel of multiple metabolites, which are still reactive and likely contribute to the toxicity of this prodrug.
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http://dx.doi.org/10.1021/acs.chemrestox.1c00164DOI Listing
August 2021

Anti-asthmatic effect of nitric oxide metallo-donor FOR811A [cis-[Ru(bpy)2(2-MIM)(NO)](PF6)3] in the respiratory mechanics of Swiss mice.

PLoS One 2021 12;16(3):e0248394. Epub 2021 Mar 12.

Department of Physiology and Pharmacology, Faculty of Medicine, Federal University of Ceará, Fortaleza, CE, Brazil.

We aimed at evaluating the anti-asthmatic effect of cis-[Ru(bpy)2(2-MIM)(NO)](PF6)3 (FOR811A), a nitrosyl-ruthenium compound, in a murine model of allergic asthma. The anti-asthmatic effects were analyzed by measuring the mechanical lung and morphometrical parameters in female Swiss mice allocated in the following groups: untreated control (Ctl+Sal) and control treated with FOR811A (Ctl+FOR), along asthmatic groups untreated (Ast+Sal) and treated with FOR811A (Ast+FOR). The drug-protein interaction was evaluated by in-silico assay using molecular docking. The results showed that the use of FOR811A in experimental asthma (Ast+FOR) decreased the pressure-volume curve, hysteresis, tissue elastance, tissue resistance, and airway resistance, similar to the control groups (Ctl+Sal; Ctl+FOR). However, it differed from the untreated asthmatic group (Ast+Sal, p<0.05), indicating that FOR811A corrected the lung parenchyma and relaxed the smooth muscles of the bronchi. Similar to control groups (Ctl+Sal; Ctl+FOR), FOR811A increased the inspiratory capacity and static compliance in asthmatic animals (Ast+Sal, p<0.05), showing that this metallodrug improved the capacity of inspiration during asthma. The morphometric parameters showed that FOR811A decreased the alveolar collapse and kept the bronchoconstriction during asthma. Beyond that, the molecular docking using FOR811A showed a strong interaction in the distal portion of the heme group of the soluble guanylate cyclase, particularly with cysteine residue (Cys141). In summary, FOR811A relaxed bronchial smooth muscles and improved respiratory mechanics during asthma, providing a protective effect and promising use for the development of an anti-asthmatic drug.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0248394PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7954307PMC
October 2021

A divergent mode of activation of a nitrosyl iron complex with unusual antiangiogenic activity.

J Inorg Biochem 2020 09 20;210:111133. Epub 2020 Jun 20.

Departamento de Química Orgânica e Inorgânica, Grupo de Bioinorgânica, Universidade Federal do Ceará-UFC, P.O Box 6021, Fortaleza, CE CEP 60440-900, Brazil. Electronic address:

Nitric oxide (NO) and nitroxyl (HNO) have gained broad attention due to their roles in several physiological and pathophysiological processes. Remarkably, these sibling species can exhibit opposing effects including the promotion of angiogenic activity by NO compared to HNO, which blocks neovascularization. While many NO donors have been developed over the years, interest in HNO has led to the recent emergence of new donors. However, in both cases there is an expressive lack of iron-based compounds. Herein, we explored the novel chemical reactivity and stability of the trans-[Fe(cyclam)(NO)Cl]Cl (cyclam = 1,4,8,11-tetraazacyclotetradecane) complex. Interestingly, the half-life (t) for NO release was 1.8 min upon light irradiation, vs 5.4 h upon thermal activation at 37 °C. Importantly, spectroscopic evidence supported the generation of HNO rather than NO induced by glutathione. Moreover, we observed significant inhibition of NO donor- or hypoxia-induced HIF-1α (hypoxia-inducible factor 1α) accumulation in breast cancer cells, as well as reduced vascular tube formation by endothelial cells pretreated with the trans-[Fe(cyclam)(NO)Cl]Cl complex. Together, these studies provide the first example of an iron-nitrosyl complex with anti-angiogenic activity as well as the potential dual activity of this compound as a NO/HNO releasing agent, which warrants further pharmacological investigation.
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http://dx.doi.org/10.1016/j.jinorgbio.2020.111133DOI Listing
September 2020

Antimicrobial activity and antibiotic synergy of a biphosphinic ruthenium complex against clinically relevant bacteria.

Biofouling 2020 04 25;36(4):442-454. Epub 2020 May 25.

Laboratório Integrado de Biomoléculas, Departamento de Patologia e Medicina Legal, Universidade Federal do Ceará, Fortaleza, CE, Brasil.

The aim of this study was to investigate the antibacterial activity, antibiotic-associated synergy, and anti-biofilm activity of the ruthenium complex, -[RuCl (dppb) (bqdi)] (RuNN). RuNN exhibited antimicrobial activity against Gram-positive bacteria with minimum inhibitory concentration (MIC) values ranging from 15.6 to 62.5 µg ml and minimum bactericidal concentration (MBC) values ranging from 62.5 to 125 µg ml. A synergistic effect against spp. was observed when RuNN was combined with ampicillin, and the range of associated fractional inhibitory concentration index (FICI) values was 0.187 to 0.312. A time-kill curve indicated the bactericidal activity of RuNN in the first 1-5 h. In general, RuNN inhibited biofilm formation and disrupted mature biofilms. Furthermore, RuNN altered the cellular morphology of biofilms. Further, RuNN did not cause hemolysis of erythrocytes. The results of this study provide evidence that RuNN is a novel therapeutic candidate to treat bacterial infections caused by biofilms.
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http://dx.doi.org/10.1080/08927014.2020.1771317DOI Listing
April 2020

Antihypertensive potential of cis-[Ru(bpy)(ImN)(NO)], a ruthenium-based nitric oxide donor.

Res Vet Sci 2020 Jun 7;130:153-160. Epub 2020 Mar 7.

Superior Institute of Biomedical Sciences, Ceará State University, Fortaleza, CE, Brazil. Electronic address:

The aim of this study was to investigate the antihypertensive properties of cis-[Ru(bpy)ImN(NO)] (FOR0811) in normotensive and in N-nitro-L-arginine methyl ester (L-NAME)-induced hypertensive rats. Vasorelaxant effects were analyzed by performing concentration response curve to FOR0811 in rat aortic rings in the absence or presence of 1H-[1,2,4]-oxadiazolo-[4,3,-a]quinoxalin-1-one (ODQ), L-cysteine or hydroxocobalamin. Normotensive and L-NAME-hypertensive rats were treated with FOR0811 and the effects in blood pressure and heart rate variability in the frequency domain (HRV) were followed. FOR0811 induced relaxation in rat aortic rings. Neither endothelium removal nor L-cysteine altered the FOR0811 effects. However, the incubation with ODQ and hydroxocobalamin completely blunted FOR0811 effects. FOR0811 administered intravenously by bolus infusion (0.01-1 mg/bolus) or chronically by using subcutaneous implanted osmotic pumps significantly reduced the mean arterial blood pressure. The effect was long lasting and did not induce reflex tachycardia. FOR0811 prevented both LF and VLF increases in L-NAME hypertensive rats and has antihypertensive properties. This new ruthenium complex compound might be a promising nitric oxide donor to treat cardiovascular diseases.
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http://dx.doi.org/10.1016/j.rvsc.2020.03.014DOI Listing
June 2020

An unusual bidentate methionine ruthenium(II) complex: photo-uncaging and antimicrobial activity.

J Biol Inorg Chem 2020 05 14;25(3):419-428. Epub 2020 Mar 14.

Departamento de Química Orgânica e Inorgânica, Universidade Federal do Ceará, Campus do Pici s/n, Cx. Postal 12200, Fortaleza, CE, 60440-900, Brazil.

The cis-[Ru(bpy)(Met)](PF) complex, where Met = L-methionine and bpy = 2,2'-bipyridine, was prepared and fully characterized. This complex was subjected to blue and green light photolysis (453 and 505 nm, respectively) in aqueous solution, leading to the release of methionine and formation of the cis-[Ru(bpy)(HO)] ion. This latter photoproduct was shown to subsequently interact with DNA, while DNA photocleavage was noticed. In agreement with these reactivities, this compound exhibited an exciting antibacterial action, particularly against Gram-positive bacteria Staphylococcus aureus and Staphylococcus epidermidis, which was enhanced upon blue light irradiation. Altogether, these results showed that our strategy was successful in producing light-triggered DNA-binding agents with pharmacological potential and a likely blocking reagent for efficient peptide chemistry formation.
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http://dx.doi.org/10.1007/s00775-020-01772-5DOI Listing
May 2020

Nitro-imidazole-based ruthenium complexes with antioxidant and anti-inflammatory activities.

J Inorg Biochem 2020 05 24;206:111048. Epub 2020 Feb 24.

Department of Organic and Inorganic Chemistry, Universidade Federal do Ceará, PO Box 6021, Fortaleza, Brazil. Electronic address:

Inflammation is a physiological process triggered in response to tissue damage, and involves events related to cell recruitment, cytokines release and reactive oxygen species (ROS) production. Failing to control the process duration lead to chronification and may be associated with the development of various pathologies, including autoimmune diseases and cancer. Considering the pharmacological potential of metal-based compounds, two new ruthenium complexes were synthesized: cis-[Ru(NO)(bpy)(5NIM)]PF (1) and cis-[RuCl(bpy)(MTZ)]PF (2), where bpy = 2,2'-bipyridine, 5NIM = 5-nitroimidazole and MTZ = metronidazole. Both products were characterized by spectroscopic techniques, followed by Density Functional Theory (DFT) calculations in order to support experimental findings. Afterwards, their in vitro cytotoxic, antioxidant and anti-inflammatory activities were investigated. Compounds 1 and 2 presented expressive in vitro antioxidant activity, reducing lipid peroxidation and decreasing intracellular ROS levels with comparable effectiveness to the standard steroidal drug dexamethasone or α-tocopherol. These complexes showed no noticeable cytotoxicity on the tested cancer cell lines. Bactericidal assay against metronidazole-resistant Helicobacter pylori, a microorganism able to disrupt oxidative balance, unraveled compound 1 moderate activity over that strain. Besides this, it was able to inhibit interleukin-6 (IL-6) and tumor necrosis factor-α (TNF- α) production as well as interleukin-1β (IL-1β) and cyclooxygenase-2 (COX-2) expression in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. This latter activity is remarkable, which has not been reported for other ruthenium-based complexes. Altogether, these results suggest cis-[Ru(NO)(bpy)(5NIM)]PF complex has potential pharmacological application as an anti-inflammatory agent that deserve further biological investigation.
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http://dx.doi.org/10.1016/j.jinorgbio.2020.111048DOI Listing
May 2020

New metallophamaceutic reduced renal injury induced by non-steroidal anti-inflammatory.

Acta Cir Bras 2020 3;34(12):e201901201. Epub 2020 Feb 3.

PhD, Full Professor, Medical School, UNICHRISTUS, Fortaleza-CE, Brazil. Conception and design of the study, acquisition and interpretation of data, manuscript preparation, critical revision.

Purpose: To evaluate the effect of Rut-bpy (Cis-[Ru(bpy)2(SO3)(NO)]PF 6), a novel nitric oxide donor, able to modulate the histological changes caused by the NASID (meloxicam).

Methods: Wistar rats were assigned into three groups (n=6 rats/group): Sham group (saline solution), NSAID group (meloxicam - 15 mg/kg) and Rut-bpy group (100 mg/kg of Rut-bpy associated with 15mg/kg of meloxicam). At the end of experiments, kidneys were removed for histological study, fractal dimension and lacunarity in all animals.

Results: At the histological examination, all animals (six animals - 100 %) in the NSAID group had membrane thickening and other changes (necrosis, acute tubular congestion and vascular congestion); on the other hand, only one animal (16.6 %) of the Rut-bpy group had congestion. The fractal dimension and lacunarity were greater in the control and Rut-bpy group than in NSAIDs group (p<0.05).

Conclusion: Rut-bpy may prevent renal histological changes in rats caused by meloxicam.
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http://dx.doi.org/10.1590/s0102-865020190120000001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6998060PMC
March 2020

In vitro and in vivo leishmanicidal activity of a ruthenium nitrosyl complex against Leishmania (Viannia) braziliensis.

Acta Trop 2019 Apr 25;192:61-65. Epub 2019 Jan 25.

School of Veterinary, Postgraduate Program in Veterinary Sciences, State University of Ceará, Fortaleza, Ceará, Brazil; Department of Pathology and Legal Medicine, School of Medicine, Specialized Medical Mycology Center, Postgraduate Program in Medical Microbiology, Federal University of Ceará, Fortaleza, Ceará, Brazil.

Leishmaniasis is a parasitic disease caused by protozoa of the genus Leishmania. There are many complications presented by the current treatment, as high toxicity, high cost and parasite resistance, making the development of new therapeutic agents indispensable. The present study aims to evaluate the leishmanicidal potential of ruthenium nitrosyl complex cis-[Ru(bpy)(SO)(NO)](PF) against Leishmania (Viannia) braziliensis. The effect of this metal complex on parasite-host interaction was evaluated by in vitro efficacy test in dermal fibrobast cells in the presence of different concentrations (1, 10, 50 and 100 μM) and by in vivo efficacy tests performed in the presence of two different concentrations of complex (100 μg/kg/day or 300 μg/kg/day) evaluating its effect on the size of the lesion and the number of parasites present in the draining lymph nodes in hamsters. Even at the lowest concentration of 1 μM of ruthenium complex, it was observed a significant decrease of the infected cells, after 24 h exposure in vitro, with total reduction at 50 μM of the ruthenium complex. In the in vivo cutaneous infection model, administration of daily doses of 300 μg/kg/day of complex reduced significantly lesion size by 51% (p < 0.05), with a 99.9% elimination of the parasites found in the lymph nodes (p < 0.001). The results suggest a promising leishmanicidal effect by that ruthenium nitrosyl complex against L. (V.) braziliensis.
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http://dx.doi.org/10.1016/j.actatropica.2019.01.021DOI Listing
April 2019

Oxygen triggers signal transduction in the DevS (DosS) sensor of Mycobacterium tuberculosis by modulating the quaternary structure.

FEBS J 2019 02 16;286(3):479-494. Epub 2019 Jan 16.

Laboratory of Bioinorganic Chemistry, Department of Organic and Inorganic Chemistry, Federal University of Ceara, Center for Sciences, Fortaleza, Brazil.

A major challenge to the control and eventual eradication of Mycobacterium tuberculosis infection is this pathogen's prolonged dormancy. The heme-based oxygen sensor protein DevS (DosS) plays a key role in this phenomenon, because it is a major activator of the transcription factor DevR. When DevS is active, its histidine protein kinase region is ON and it phosphorylates and activates DevR, which can induce the transcription of the dormancy regulon genes. Here, we have investigated the mechanism by which the ligation of molecular oxygen to a heme-binding domain in DevS switches OFF its histidine protein kinase region. To shed light on the oligomerization states of this protein and possible protein-surfaces of interaction, we used analytical gel filtration, together with dynamic light scattering, fluorescence spectroscopy and chemical crosslinking. We found that DevS exists as three major species: an octamer, a tetramer and a dimer. These three states were observed for the concentration range between 0.5 and 20 μm DevS, but not below 0.1 μm. Levels of DevS in M. tuberculosis are expected to range from 5 to 26 μm. When this histidine protein kinase was OFF, the DevS was mainly tetrameric and dimeric; by contrast, when the kinase was ON, the protein was predominantly octameric. The changes in quaternary structure were rapid upon binding to the physiological signal. This finding represents a novel strategy for switching the activity of a two-component heme-based sensor. An enhanced understanding of this process might potentially lead to the design of novel regulatory agents that target the multimer interfaces for treatment of latent tuberculosis.
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http://dx.doi.org/10.1111/febs.14734DOI Listing
February 2019

Synthesis and mechanistic investigation of iron(II) complexes of isoniazid and derivatives as a redox-mediated activation strategy for anti-tuberculosis therapy.

J Inorg Biochem 2018 02 21;179:71-81. Epub 2017 Nov 21.

CNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, BP 44099, F-31077 Toulouse, Cedex 4, France; Université de Toulouse, UPS, INPT, F-31077 Toulouse, Cedex 4, France. Electronic address:

The emergence of multidrug-resistant strains of Mycobacterium tuberculosis (MTB) represents a major threat to global health. Isoniazid (INH) is a prodrug used in the first-line treatment of tuberculosis. It undergoes oxidation by a catalase-peroxidase KatG, leading to generation of an isonicotinoyl radical that reacts with NAD(H) forming the INH-NADH adduct as the active metabolite. A redox-mediated activation of isoniazid using an iron metal complex was previously proposed as a strategy to overcome isoniazid resistance due to KatG mutations. Here, we have prepared a series of iron metal complexes with isoniazid and analogues, containing alkyl substituents at the hydrazide moiety, and also with pyrazinamide derivatives. These complexes were activated by HO and studied by ESR and LC-MS. For the first time, the formation of the oxidized INH-NAD adduct from the pentacyano(isoniazid)ferrate(II) complex was detected by LC-MS, supporting a redox-mediated activation, for which a mechanistic proposition is reported. ESR data showed all alkylated hydrazides, in contrast to non-substituted hydrazides, only generated alkyl-based radicals. The structural modifications did not improve minimal inhibitory concentration (MIC) against MTB in comparison to isoniazid iron complex, providing support to isonicotinoyl radical formation as a requirement for activity. Nonetheless, the pyrazinoic acid hydrazide iron complex showed redox-mediated activation using HO with generation of a pyrazinoyl radical intermediate and production of pyrazinoic acid, which is in fact the active metabolite of pyrazinamide prodrug. Thereby, this strategy can also unveil new opportunities for activation of this type of drug.
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http://dx.doi.org/10.1016/j.jinorgbio.2017.11.013DOI Listing
February 2018

Drug discovery targeting heme-based sensors and their coupled activities.

J Inorg Biochem 2017 02 20;167:12-20. Epub 2016 Nov 20.

Department of Biochemistry, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9038, USA. Electronic address:

Heme-based sensors have emerged during the last 20years as being a large family of proteins that occur in all kingdoms of life. A myriad of biological adaptations are associated with these sensors, which include vasodilation, bacterial virulence, dormancy, chemotaxis, biofilm formation, among others. Due to the key activities regulated by these proteins along with many other systems that use similar output domains, there is a growing interest in developing small molecules as their regulators. Here, we review the development of potential activators and inhibitors for many of these systems, including human soluble guanylate cyclase, c-di-GMP-related enzymes, Mycobacterium tuberculosis DevR/DevS/DosT (differentially expressed in virulent strain response regulator/sensor/dormancysurvival sensorT), the Rev-erb-α and β nuclear receptor, among others. The possible roles of these molecules as biochemical tools, therapeutic agents, and novel antibiotics are critically examined.
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http://dx.doi.org/10.1016/j.jinorgbio.2016.11.022DOI Listing
February 2017

Antileishmanial Activity and Inducible Nitric Oxide Synthase Activation by RuNO Complex.

Mediators Inflamm 2016 4;2016:2631625. Epub 2016 Oct 4.

Department of Pathological Sciences, Center of Biological Sciences, State University of Londrina, 86057-970 Londrina, PR, Brazil.

Parasites of the genus are capable of inhibiting effector functions of macrophages. These parasites have developed the adaptive ability to escape host defenses; for example, they inactivate the NF-B complex and suppress iNOS expression in infected macrophages, which are responsible for the production of the major antileishmanial substance nitric oxide (NO), favoring then its replication and successful infection. Metal complexes with NO have been studied as potential compounds for the treatment of certain tropical diseases, such as ruthenium compounds, known to be exogenous NO donors. In the present work, the compound -[Ru(bpy)SO(NO)]PF, or RuNO, showed leishmanicidal activity directly and indirectly on promastigote forms of . In addition, treatment with RuNO increased NO production by reversing the depletion of NO caused by . We also found increased expression of Akt, iNOS, and NF-B in infected and treated macrophages. These results demonstrated that RuNO was able to kill the parasite by NO release and modulate the transcriptional capacity of the cell.
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http://dx.doi.org/10.1155/2016/2631625DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5067336PMC
June 2017

The Heme-Based Oxygen Sensor Rhizobium etli FixL: Influence of Auxiliary Ligands on Heme Redox Potential and Implications on the Enzyme Activity.

J Inorg Biochem 2016 11 26;164:34-41. Epub 2016 Aug 26.

School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, 4072, Australia. Electronic address:

Conformational changes associated to sensing mechanisms of heme-based protein sensors are a key molecular event that seems to modulate not only the protein activity but also the potential of the Fe redox couple of the heme domain. In this work, midpoint potentials (E) assigned to the Fe redox couple of the heme domain of FixL from Rhizobium etli (ReFixL) in the unliganded and liganded states were determined by spectroelectrochemistry in the presence of inorganic mediators. In comparison to the unliganded ReFixL protein (+19mV), the binding to ligands that switch off the kinase activity induces a negative shift, i. e. E=-51, -57 and -156mV for O, imidazole and CN, respectively. Upon binding to CO, which does not affect the kinase active, E was observed at +21mV. The potential values observed for Fe of the heme domain of ReFixL upon binding to CO and O do not follow the expected trend based on thermodynamics, assuming that positive potential shift would be expected for ligands that bind to and therefore stabilize the Fe state. Our results suggest that the conformational changes that switch off kinase activity upon O binding have knock-on effects to the local environment of the heme, such as solvent rearrangement, destabilize the Fe state and counterbalances the Fe-stabilizing influence of the O ligand.
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http://dx.doi.org/10.1016/j.jinorgbio.2016.08.009DOI Listing
November 2016

Thiol-Activated HNO Release from a Ruthenium Antiangiogenesis Complex and HIF-1α Inhibition for Cancer Therapy.

ACS Chem Biol 2016 07 31;11(7):2057-65. Epub 2016 May 31.

Department of Chemistry, University of Warwick , Coventry CV4 7AL, United Kingdom.

Metallonitrosyl complexes are promising as nitric oxide (NO) donors for the treatment of cardiovascular, endothelial, and pathogenic diseases, as well as cancer. Recently, the reduced form of NO(-) (protonated as HNO, nitroxyl, azanone, isoelectronic with O2) has also emerged as a candidate for therapeutic applications including treatment of acute heart failure and alcoholism. Here, we show that HNO is a product of the reaction of the Ru(II) complex [Ru(bpy)2(SO3)(NO)](+) (1) with glutathione or N-acetyl-L-cysteine, using met-myoglobin and carboxy-PTIO (2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) as trapping agents. Characteristic absorption spectroscopic profiles for HNO reactions with met-myoglobin were obtained, as well as EPR evidence from carboxy-PTIO experiments. Importantly, the product HNO counteracted NO-induced as well as hypoxia-induced stabilization of the tumor-suppressor HIF-1α in cancer cells. The functional disruption of neovascularization by HNO produced by this metallonitrosyl complex was demonstrated in an in vitro angiogenesis model. This behavior is consistent with HNO biochemistry and contrasts with NO-mediated stabilization of HIF-1α. Together, these results demonstrate for the first time thiol-dependent production of HNO by a ruthenium complex and subsequent destabilization of HIF-1α. This work suggests that the complex warrants further investigation as a promising antiangiogenesis agent for the treatment of cancer.
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http://dx.doi.org/10.1021/acschembio.6b00222DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4949585PMC
July 2016

Nitric oxide and Brazilian propolis combined accelerates tissue repair by modulating cell migration, cytokine production and collagen deposition in experimental leishmaniasis.

PLoS One 2015 14;10(5):e0125101. Epub 2015 May 14.

Department of Pathology Science, Center of Biological Sciences, State University of Londrina, Londrina, Paraná, Brazil.

The fact that drugs currently used in the treatment of Leishmania are highly toxic and associated with acquired resistance has promoted the search for new therapies for treating American tegumentary leishmaniasis (ATL). In this study, BALB/c mice were injected in the hind paw with Leishmania (Leishmania) amazonensis and subsequently treated with a combination of nitric oxide (NO) donor (cis-[Ru(bpy) 2imN(NO)](PF6)3) (Ru-NO), given by intraperitoneal injection, and oral Brazilian propolis for 30 days. Ru-NO reached the center of the lesion and increased the NO level in the injured hind paw without lesion exacerbation. Histological and immunological parameters of chronic inflammation showed that this combined treatment increased the efficacy of macrophages, determined by the decrease in the number of parasitized cells, leading to reduced expression of proinflammatory and tissue damage markers. In addition, these drugs in combination fostered wound healing, enhanced the number of fibroblasts, pro-healing cytokines and induced collagen synthesis at the lesion site. Overall, our findings suggest that the combination of the NO donor Ru-NO and Brazilian propolis alleviates experimental ATL lesions, highlighting a new therapeutic option that can be considered for further in vivo investigations as a candidate for the treatment of cutaneous leishmaniasis.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0125101PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4431861PMC
April 2016

[Fe(CN)5(isoniazid)](3-): an iron isoniazid complex with redox behavior implicated in tuberculosis therapy.

J Inorg Biochem 2014 Nov 12;140:236-44. Epub 2014 Aug 12.

Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom. Electronic address:

Tuberculosis has re-emerged as a worldwide threat, which has motivated the development of new drugs. The antituberculosis complex Na3[Fe(CN)5(isoniazid)] (IQG607) in particular is of interest on account of its ability to overcome resistance. IQG607 has the potential for redox-mediated-activation, in which an acylpyridine (isonicotinoyl) radical could be generated without assistance from the mycobacterial KatG enzyme. Here, we have investigated the reactivity of IQG607 toward hydrogen peroxide and superoxide, well-known intracellular oxidizing agents that could play a key role in the redox-mediated-activation of this compound. HPLC, NMR and electronic spectroscopy studies showed a very fast oxidation rate for bound isoniazid, over 460-fold faster than free isoniazid oxidation. A series of EPR spin traps were used for detection of isonicotinoyl and derived radicals bound to iron. This is the first report for an isonicotinoyl radical bound to a metal complex, supported by (14)N and (1)H hyperfine splittings for the POBN and PBN trapped radicals. POBN and PBN exhibited average hyperfine coupling constants of aN=15.6, aH=2.8 and aN=15.4, aH=4.7, respectively, which are in close agreement to the isonicotinoyl radical. Radical generation is thought to play a major role in the mechanism of action of isoniazid and this work provides strong evidence for its production within IQG607, which, along with biological and chemical oxidation data, support a redox-mediated activation mechanism. More generally the concept of redox activation of metallo prodrugs could be applied more widely for the design of therapeutic agents with novel mechanisms of action.
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http://dx.doi.org/10.1016/j.jinorgbio.2014.08.002DOI Listing
November 2014

Activity of IQG-607, a new orally active compound, in a murine model of Mycobacterium tuberculosis infection.

Int J Antimicrob Agents 2012 Aug 27;40(2):182-5. Epub 2012 Jun 27.

Centro de Pesquisas em Biologia Molecular e Funcional (CPBMF) and Instituto Nacional de Ciência e Tecnologia em Tuberculose (INCT-TB), Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Av. Ipiranga 6681 - Prédio 92A Tecnopuc, 90619-900 Porto Alegre, RS, Brazil.

We have previously demonstrated a potent in vitro inhibitory activity for two pentacyano(isoniazid)ferrate(II) compounds, namely IQG-607 and IQG-639, against the Mycobacterium tuberculosis enoyl-acyl carrier protein reductase enzyme. In this study, the activity of these compounds was evaluated using an in vivo murine model of tuberculosis. Swiss mice were infected with M. tuberculosis H37Rv strain and then IQG-607 or IQG-639 (250 mg/kg) was administered for 28 days or 56 days. In addition, a dose-response study was performed with IQG-607 at 5, 10, 25, 50, 100, 200 and 250 mg/kg. The activity of test compounds was compared with that of the positive control drug isoniazid (INH) (25 mg/kg). After 28 days or 56 days of treatment, both IQG-607 and INH significantly reduced M. tuberculosis-induced splenomegaly as well as significantly diminishing the colony-forming units in the spleen and lungs. IQG-607 and INH ameliorated the lung macroscopic aspect, reducing lung lesions to a similar extent. However, IQG-639 did not significantly modify any evaluated parameter. Experiments using early and late controls of infection revealed a bactericidal activity for IQG-607. IQG-607 might well represent a good candidate for clinical development as a new antimycobacterial agent.
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http://dx.doi.org/10.1016/j.ijantimicag.2012.04.019DOI Listing
August 2012

Preconditioning with a novel metallopharmaceutical NO donor in anesthetized rats subjected to brain ischemia/reperfusion.

Neurochem Res 2012 Apr 10;37(4):749-58. Epub 2011 Dec 10.

Department of Surgery, Federal University of Ceará, R. Professor Costa Mendes, 1608/3º Andar, Fortaleza, CE, CEP:60430-140, Brazil.

Rut-bpy is a novel nitrosyl-ruthenium complex releasing NO into the vascular system. We evaluated the effect of Rut-bpy (100 mg/kg) on a rat model of brain stroke. Forty rats were assigned to four groups (Saline solution [SS], Rut-bpy, SS+ischemia-reperfusion [SS+I/R] and Rut-bpy+ischemia-reperfusion [Rut-bpy+I/R]) with their mean arterial pressure (MAP) continuously monitored. The groups were submitted (SS+I/R and Rut-bpy+I/R) or not (SS and Rut-bpy) to incomplete global brain ischemia by occlusion of the common bilateral carotid arteries during 30 min followed by reperfusion for further 60 min. Thirty minutes before ischemia, rats were treated pairwise by intraperitoneal injection of saline solution or Rut-bpy. At the end of experiments, brain was removed for triphenyltetrazolium chloride staining in order to quantify the total ischemic area. In a subset of rats, hippocampus was obtained for histopathology scoring, nitrate and nitrite measurements, immunostaining and western blotting of the nuclear factor- κB (NF-κB). Rut-bpy pre-treatment decreased MAP variations during the transition from brain ischemia to reperfusion and decreased the fractional injury area. Rut-bpy pre-treatment reduced NF-κB hippocampal immunostaining and protein expression with improved histopathology scoring as compared to the untreated operated control. In conclusion, Rut-bpy improved the total brain infarction area and hippocampal neuronal viability in part by inhibiting NF-κB signaling and helped to stabilize the blood pressure during the transition from ischemia to reperfusion.
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http://dx.doi.org/10.1007/s11064-011-0669-xDOI Listing
April 2012

Effects of Rut-bpy (Cis-[Ru(bpy)2(SO3)(NO)]PF 6), a novel nitric oxide donor, in L-NAME-induced hypertension in rats.

Acta Cir Bras 2011 ;26 Suppl 1:57-9

Department of Surgery, Federal University of Ceara, Fortaleza-CE, Brazil.

Purpose: To evaluate the effect of Rut-bpy (Cis-[Ru(bpy)2(SO3)(NO)]PF 6), a novel nitric oxide donor in Nω-nitro-L-arginine methyl ester (L-NAME)-induced hypertensive rats.

Methods: Twenty-four male Wistar rats were randomly assigned to four groups (n=6), named according to the treatment applied (G1-Saline, G2-Rut-bpy, G3-L-NAME and G4-L-NAME+Rut-bpy). L-NAME (30 mg/Kg) was injected intraperitoneally 30 minutes before the administration of Rut-bpy (100 mg/Kg). Mean abdominal aorta arterial blood pressure (MAP) was continuously monitored.

Results: Mean arterial blood pressure (MAP) in G3 rats rose progressively, reaching 147±16 mmHg compared with 100±19 mm Hg in G1 rats (p<0.05). In G4 rats, treated with L-NAME+Rut-bpy, MAP reached 149+11 mm Hg while in G2 rats, treated with Rut-bpy, MAP values were 106±11 mm Hg. In G1 rats these values decreased progressively reaching 87+14 mm Hg after 30 minutes. An important finding was the maintenance of the MAP throughout the experiment in G2 rats.

Conclusion: Rut-bpy does not decrease the MAP in L-Name induced hypertensive rats. However, when it is used in anesthetized hypotensive rats a stable blood pressure is obtained.
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http://dx.doi.org/10.1590/s0102-86502011000700012DOI Listing
June 2012

Isoniazid metal complex reactivity and insights for a novel anti-tuberculosis drug design.

J Biol Inorg Chem 2012 Feb 28;17(2):275-83. Epub 2011 Sep 28.

Departamento de Química Orgânica e Inorgânica, Laboratório de Bioinorgânica, Universidade Federal do Ceará, P.O. Box 6021, Fortaleza, 60455-970, Brazil.

For over a decade, tuberculosis (TB) has been the leading cause of death among infectious diseases. Since the 1950s, isoniazid has been used as a front-line drug in the treatment of TB; however, resistant TB strains have limited its use. The major route of isoniazid resistance relies on KatG enzyme disruption, which does not promote an electron transfer reaction. Here, we investigated the reactivity of isoniazid metal complexes as prototypes for novel self-activating metallodrugs against TB with the aim to overcome resistance. Reactivity studies were conducted with hydrogen peroxide, hexacyanoferrate(III), and aquopentacyanoferrate(III). The latter species showed a preference for the inner-sphere electron transfer reaction pathway. Additionally, electron transfer reaction performed with either free isoniazid or (isoniazid)pentacyanoferrate(II) complex resulted in similar oxidized isoniazid derivatives as observed when the KatG enzyme was used. However, upon metal coordination, a significant enhancement in the formation of isonicotinic acid was observed compared with that of isonicotinamide. These results suggest that the pathway of a carbonyl-centered radical might be favored upon coordination to the Fe(II) owing to the π-back-bonding effect promoted by this metal center; therefore, the isoniazid metal complex could serve as a potential metallodrug. Enzymatic inhibition assays conducted with InhA showed that the cyanoferrate moiety is not the major player involved in this inhibition but the presence of isoniazid is required in this process. Other isoniazid metal complexes, [Ru(CN)(5)(izd)](3-) and [Ru(NH(3))(5)(izd)](2+) (where izd is isoniazid), were also unable to inhibit InhA, supporting our proposed self-activating mechanism of action. We propose that isoniazid reactivity can be rationally modulated by metal coordination chemistry, leading to the development of novel anti-TB metallodrugs.
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http://dx.doi.org/10.1007/s00775-011-0848-xDOI Listing
February 2012

Experimental chemotherapy in paracoccidioidomycosis using ruthenium NO donor.

Mycopathologia 2011 Aug 25;172(2):95-107. Epub 2011 Mar 25.

Department of Pathology Science, CCB, State University of Londrina-UEL, Londrina, PR, Brazil.

Paracoccidioidomycosis (PCM) is a granulomatous disease caused by a dimorphic fungus, Paracoccidioides brasiliensis (Pb). To determine the influence of nitric oxide (NO) on this disease, we tested cis-[Ru(bpy)2(NO)SO3](PF6), ruthenium nitrosyl, which releases NO when activated by biological reducing agents, in BALB/c mice infected intravenously with Pb 18 isolate. In a previous study by our group, the fungicidal activity of ruthenium nitrosyl was evaluated in a mouse model of acute PCM, by measuring the immune cellular response (DTH), histopathological characteristics of the granulomatous lesions (and numbers), cytokines, and NO production. We found that cis-[Ru(bpy)2(NO)SO3](PF6)-treated mice were more resistant to infection, since they exhibited higher survival when compared with the control group. Furthermore, we observed a decreased influx of inflammatory cells in the lung and liver tissue of treated mice, possibly because of a minor reduction in fungal cell numbers. Moreover, an increased production of IL-10 and a decrease in TNF-α levels were detected in lung tissues of infected mice treated with cis-[Ru(bpy)2(NO)SO3](PF6). Immunohistochemistry showed that there was no difference in the number of VEGF- expressing cells. The animals treated with cis-[Ru(bpy)2(NO)SO3](PF6) showed high NO levels at 40 days after infection. These results show that NO is effectively involved in the mechanism that regulates the immune response in lung of Pb-infected mice. These data suggest that NO is a resistance factor during paracoccidioidomycosis by controlling fungal proliferation, influencing cytokine production, and consequently moderating the development of a strong inflammatory response.
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http://dx.doi.org/10.1007/s11046-011-9416-8DOI Listing
August 2011

Release of NO by a nitrosyl complex upon activation by the mitochondrial reducing power.

J Inorg Biochem 2002 Apr;89(3-4):267-71

Instituto de Química de São Carlos, Universidade de São Paulo, Av. Trabalhador São Carlense 400, CP 780, 13560-970, Brazil.

The reaction of trans-[Ru(NH(3))(4)P(OEt)(3)NO](3+) and mitochondria was investigated through differential pulse polarography and fluorimetry. The nitrosyl complex undergoes one-electron reduction centered on the NO ligand site. The reaction between the mitochondrial reductor and trans-[Ru(NH(3))(4)P(OEt)(3)NO](3+) exhibits a second order specific rate constant calculated as k=2 x 10(1) M(-1) s(-1). The reduced species, trans-[Ru(NH(3))(4)P(OEt)(3)NO](2+), quickly releases NO, yielding trans-[Ru(NH(3))(4)P(OEt)(3)H(2)O](2+). The low toxicities of both trans-[Ru(NH(3))(4)P(OEt)(3)(NO)](2+) and trans-[Ru(NH(3))(4)P(OEt)(3)H(2)O](2+) and its ability to release NO after reductive activation in a biological medium make the nitrosyl compound a useful model of a hypotensive drug.
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http://dx.doi.org/10.1016/s0162-0134(01)00414-7DOI Listing
April 2002
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