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Sahoo P, Pathak NK, Scott Bohle D, Dodd EL, Tripathy U. Hematin anhydride ( β-hematin): An analogue to malaria pigment hemozoin possesses nonlinearity. Spectrochim Acta A Mol Biomol Spectrosc 2024; 310:123902. [PMID: 38281463 DOI: 10.1016/j.saa.2024.123902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 12/08/2023] [Accepted: 01/15/2024] [Indexed: 01/30/2024]
Abstract
Hematin anhydride (β-hematin), the synthetic analogue of the malaria pigment, "hemozoin", is a heme dimer produced by reciprocal covalent bonds among carboxylic acid groups on the protoporphyrin-IX ring and the iron atom present in the two adjacent heme molecules. Hemozoin is a disposal product formed from the digestion of hemoglobin present in the red blood cells infected with hematophagous malaria parasites. Besides, as the parasites invade red blood cells, hemozoin crystals are eventually released into the bloodstream, where they accumulate over time in tissues. Severe malaria infection leads to significant dysfunction in vital organs such as the liver, spleen, and brain in part due to the autoimmune response to the excessive accumulation of hemozoin in these tissues. Also, the amount of these crystals in the vasculature correlates with disease progression. Thus, hemozoin is a unique indicator of infection used as a malaria biomarker and hence, used as a target for the development of antimalarial drugs. Hence, exploring various properties of hemozoin is extremely useful in the direction of diagnosis and cure. The present study focuses on finding one of the unknown properties of β-hematin in physiological conditions by using the Z-scan technique, which is simple, sensitive, and economical. It is observed that hemozoin possesses one of the unique material properties, i.e., nonlinearity with a detection limit of ∼ 15 µM. The self-defocusing action causes β-hematin to exhibit negative refractive nonlinearity. The observed data is analyzed with a thermal lensing model. We strongly believe that our simple and reliable approach to probing the nonlinearity of β-hematin will provide fresh opportunities for malaria diagnostics & cure in the near future.
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Affiliation(s)
- Priyadarshi Sahoo
- Department of Physics, Indian Institute of Technology (Indian School of Mines), Dhanbad 826004, Jharkhand, India
| | - Nitesh Kumar Pathak
- Department of Physics, Indian Institute of Technology (Indian School of Mines), Dhanbad 826004, Jharkhand, India
| | - D Scott Bohle
- Department of Chemistry, McGill University, Montreal H3A 0B8, Quebec, Canada
| | - Erin L Dodd
- Département de Chimie, Université du Québec à Montréal, 2101, rue Jeanne-Mance Montréal, H2X 2J6 Québec, Canada
| | - Umakanta Tripathy
- Department of Physics, Indian Institute of Technology (Indian School of Mines), Dhanbad 826004, Jharkhand, India.
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Singh R, Singh R, Srihari V, Makde RD. In Vitro Investigation Unveiling New Insights into the Antimalarial Mechanism of Chloroquine: Role in Perturbing Nucleation Events during Heme to β-Hematin Transformation. ACS Infect Dis 2023; 9:1647-1657. [PMID: 37471056 DOI: 10.1021/acsinfecdis.3c00278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/21/2023]
Abstract
Malaria parasites generate toxic heme during hemoglobin digestion, which is neutralized by crystallizing into inert hemozoin (β-hematin). Chloroquine blocks this detoxification process, resulting in heme-mediated toxicity in malaria parasites. However, the exact mechanism of chloroquine's action remains unknown. This study investigates the impact of chloroquine on the transformation of heme into β-hematin. The results show that chloroquine does not completely halt the transformation process but rather slows it down. Additionally, chloroquine complexation with free heme does not affect substrate availability or inhibit β-hematin formation. Scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) studies indicate that the size of β-hematin crystal particles and crystallites increases in the presence of chloroquine, suggesting that chloroquine does not impede crystal growth. These findings suggest that chloroquine delays hemozoin production by perturbing the nucleation events of crystals and/or the stability of crystal nuclei. Thus, contrary to prevailing beliefs, this study provides a new perspective on the working mechanism of chloroquine.
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Affiliation(s)
- Rahul Singh
- Beamline Development and Application Section, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Mumbai 400085, India
| | - Rashmi Singh
- Laser & Functional Materials Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, India
| | - Velaga Srihari
- High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai 40008, Maharashtra, India
| | - Ravindra D Makde
- Beamline Development and Application Section, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Mumbai 400085, India
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3
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Olivier T, Loots L, Kok M, de Villiers M, Reader J, Birkholtz LM, Arnott GE, de Villiers KA. Adsorption to the surface of hemozoin crystals: Structure-based design and synthesis of new amino-phenoxazine β-hematin inhibitors. ChemMedChem 2022; 17:e202200139. [PMID: 35385211 DOI: 10.1002/cmdc.202200139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 04/05/2022] [Indexed: 11/07/2022]
Abstract
In silico adsorption of eight antimalarials that inhibit β-hematin (synthetic hemozoin) formation identified a primary binding site on the (001) face, which accommodates inhibitors via formation of predominantly π-π interactions. A good correlation (r2 = 0.64, P = 0.017) between adsorption energies and the logarithm of β-hematin inhibitory activity was found for this face. Of 53 monocyclic, bicyclic and tricyclic scaffolds, the latter yielded the most favorable adsorption energies. Five new amino-phenoxazine compounds were pursued as β-hematin inhibitors based on adsorption behaviour. The 2-substituted phenoxazines show good to moderate β-hematin inhibitory activity (< 100 μM) and Plasmodium falciparum blood stage activity against the 3D7 strain. N1,N1-diethyl-N4-(10H-phenoxazin-2-yl)pentane-1,4-diamine (P2a) is the most promising hit with IC50 values of 4.7 ± 0.6 and 0.64 ± 0.05 μM, respectively. Adsorption energies are predictive of β-hematin inhibitory activity, and thus the in silico approach is a beneficial tool for structure-based development of new non-quinoline inhibitors.
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Affiliation(s)
- Tania Olivier
- Stellenbosch University Faculty of Science, Chemistry and Polymer Science, SOUTH AFRICA
| | - Leigh Loots
- Stellenbosch University Faculty of Science, Chemistry and Polymer Science, SOUTH AFRICA
| | - Michélle Kok
- Stellenbosch University Faculty of Science, Biochemistry, SOUTH AFRICA
| | | | - Janette Reader
- University of Pretoria, Biochemistry, Genetics and Microbiology, SOUTH AFRICA
| | - Lyn-Marié Birkholtz
- University of Pretoria, Biochemistry, Genetics and Microbiology, SOUTH AFRICA
| | - Gareth E Arnott
- Stellenbosch University Faculty of Science, Chemistry and Polymer Science, 49 Almond Drive, Helderberg Estate, 7130, Somerset West, SOUTH AFRICA
| | - Katherine A de Villiers
- Stellenbosch University Faculty of Science, Chemistry and Polymer Science, Merriman Avenue, 7600, Stellenbosch, SOUTH AFRICA
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Obisesan OR, Adekunle AS, Oyekunle JAO, Sabu T, Nkambule TTI, Mamba BB. Development of Electrochemical Nanosensor for the Detection of Malaria Parasite in Clinical Samples. Front Chem 2019; 7:89. [PMID: 30859097 PMCID: PMC6397833 DOI: 10.3389/fchem.2019.00089] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2018] [Accepted: 02/04/2019] [Indexed: 12/24/2022] Open
Abstract
In this study, electrochemical nanosensors were developed from the synthesized metal oxide (MO) nanoparticles by supporting it on a gold electrode (Au). The activity of the developed nanosensor toward the detection of malaria biomarker (β-hematin) was determined and the optimum conditions at which the maximum detection and quantification occurred were established. β-Hematin current response at the sensors was higher when compared with the bare Au electrode and followed the order Au-CuO (C) > Au-CuO (M) > Au-Fe2O3 (M) > Au-Fe2O3 (C) > Au-Al2O3 (M) > Au-Al2O3 (C) > bare Au. The developed sensors were stable with a relatively low current drop (10.61-17.35 %) in the analyte. Au-CuO sensor had the best performance toward the biomarker and quantitatively detected P. berghei in infected mice's serum samples at 3.60-4.8 mM and P. falciparum in human blood serum samples at 0.65-1.35 mM concentration.
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Affiliation(s)
- Olaoluwa R Obisesan
- Department of Chemistry, Obafemi Awolowo University, Ile-Ife, Nigeria.,International and Inter University Center for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, India
| | | | - John A O Oyekunle
- Department of Chemistry, Obafemi Awolowo University, Ile-Ife, Nigeria
| | - Thomas Sabu
- International and Inter University Center for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, India
| | - Thabo T I Nkambule
- Nanotechnology and Water Sustainability Research Unit, College of Science, Engineering and Technology, Univeristy of South Africa, Johannesburg, South Africa
| | - Bhekie B Mamba
- Nanotechnology and Water Sustainability Research Unit, College of Science, Engineering and Technology, Univeristy of South Africa, Johannesburg, South Africa
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5
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Kumar M, Okombo J, Mambwe D, Taylor D, Lawrence N, Reader J, van der Watt M, Fontinha D, Sanches-Vaz M, Bezuidenhout BC, Lauterbach SB, Liebenberg D, Birkholtz LM, Coetzer TL, Prudêncio M, Egan TJ, Wittlin S, Chibale K. Multistage Antiplasmodium Activity of Astemizole Analogues and Inhibition of Hemozoin Formation as a Contributor to Their Mode of Action. ACS Infect Dis 2019; 5:303-315. [PMID: 30525439 DOI: 10.1021/acsinfecdis.8b00272] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A drug repositioning approach was leveraged to derivatize astemizole (AST), an antihistamine drug whose antimalarial activity was previously identified in a high-throughput screen. The multistage activity potential against the Plasmodium parasite's life cycle of the subsequent analogues was examined by evaluating against the parasite asexual blood, liver, and sexual gametocytic stages. In addition, the previously reported contribution of heme detoxification to the compound's mode of action was interrogated. Ten of the 17 derivatives showed half-maximal inhibitory concentrations (IC50s) of <0.1 μM against the chloroquine (CQ)-sensitive Plasmodium falciparum NF54 ( PfNF54) strain while maintaining submicromolar potency against the multidrug-resistant strain, PfK1, with most showing low likelihood of cross-resistance with CQ. Selected analogues ( PfNF54-IC50 < 0.1 μM) were tested for cytotoxicity on Chinese hamster ovarian (CHO) cells and found to be highly selective (selectivity index > 100). Screening of AST and its analogues against gametocytes revealed their moderate activity (IC50: 1-5 μM) against late stage P. falciparum gametocytes, while the evaluation of activity against P. berghei liver stages identified one compound (3) with 3-fold greater activity than the parent AST compound. Mechanistic studies showed a strong correlation between in vitro inhibition of β-hematin formation by the AST derivatives and their antiplasmodium IC50s. Analyses of intracellular inhibition of hemozoin formation within the parasite further yielded signatures attributable to a possible perturbation of the heme detoxification machinery.
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Affiliation(s)
- Malkeet Kumar
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - John Okombo
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Dickson Mambwe
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Dale Taylor
- Drug Discovery and Development Centre (H3D), Division of Clinical Pharmacology, Department of Medicine, University of Cape Town, Observatory 7925, South Africa
| | - Nina Lawrence
- Drug Discovery and Development Centre (H3D), Division of Clinical Pharmacology, Department of Medicine, University of Cape Town, Observatory 7925, South Africa
| | - Janette Reader
- Department of Biochemistry, Genetics and Microbiology, Institute for Sustainable Malaria Control, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Mariëtte van der Watt
- Department of Biochemistry, Genetics and Microbiology, Institute for Sustainable Malaria Control, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Diana Fontinha
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Av. Prof. Egas Moniz, 1649-028 Lisboa, Portugal
| | - Margarida Sanches-Vaz
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Av. Prof. Egas Moniz, 1649-028 Lisboa, Portugal
| | - Belinda C. Bezuidenhout
- Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and National Health Laboratory Service, Johannesburg 2193, South Africa
| | - Sonja B. Lauterbach
- Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and National Health Laboratory Service, Johannesburg 2193, South Africa
| | - Dale Liebenberg
- Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and National Health Laboratory Service, Johannesburg 2193, South Africa
| | - Lyn-Marie Birkholtz
- Department of Biochemistry, Genetics and Microbiology, Institute for Sustainable Malaria Control, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Theresa L. Coetzer
- Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and National Health Laboratory Service, Johannesburg 2193, South Africa
| | - Miguel Prudêncio
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Av. Prof. Egas Moniz, 1649-028 Lisboa, Portugal
| | - Timothy J. Egan
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Rondebosch 7701, South Africa
| | - Sergio Wittlin
- Swiss Tropical and Public Health Institute, Socinstrasse 57, 4002 Basel, Switzerland
- University of Basel, 4003 Basel, Switzerland
| | - Kelly Chibale
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Rondebosch 7701, South Africa
- South African Medical Research Council Drug Discovery and Development Research Unit, Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
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6
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Roch A, Prodéo J, Pierart C, Muller RN, Duez P. The paramagnetic properties of malaria pigment, hemozoin, yield clues to a low-cost system for its trapping and determination. Talanta 2019; 197:553-557. [PMID: 30771975 DOI: 10.1016/j.talanta.2019.01.090] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 01/22/2019] [Accepted: 01/24/2019] [Indexed: 11/27/2022]
Abstract
The binding of malaria pigment, hemozoin, by a gradient magnetic field has been investigated in a manual trapping column system. Two types of magnetic filling have been tested to produce field gradients: nickel-plated steel wires, wrapped around a steel core, and superparamagnetic microbeads. The latter system allows an efficient trapping (> 80%) of β-hematin (a synthetic pigment with physical and paramagnetic properties analogous to those of hemozoin). Tests with a Plasmodium falciparum 3D7 culture indicate that hemozoin is similarly trapped. Off-line optical spectroscopy measurements present limited sensitivity as the hemozoin we detected from in vitro cultured parasites would correspond to only a theoretical 0.02% parasitemia (1000 parasites/µL). Further work needs to be undertaken to reduce this threshold to a practical detectability level. Based on these data, a magneto-chromatographic on-line system with reduced dead volumes is proposed as a possible low-cost instrument to be tested as a malaria diagnosis system.
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Affiliation(s)
- A Roch
- Service de Chimie Générale, Organique et Biomédicale, Université de Mons (UMONS), Bât. Mendeleïev, Avenue Maistriau 19, 7000 Mons, Belgium
| | - J Prodéo
- Service de Chimie Générale, Organique et Biomédicale, Université de Mons (UMONS), Bât. Mendeleïev, Avenue Maistriau 19, 7000 Mons, Belgium
| | - C Pierart
- Service de Chimie Générale, Organique et Biomédicale, Université de Mons (UMONS), Bât. Mendeleïev, Avenue Maistriau 19, 7000 Mons, Belgium
| | - R N Muller
- Service de Chimie Générale, Organique et Biomédicale, Université de Mons (UMONS), Bât. Mendeleïev, Avenue Maistriau 19, 7000 Mons, Belgium
| | - P Duez
- Service de Chimie Thérapeutique et de Pharmacognosie, Université de Mons (UMONS), Bât. 6, Chemin du Champ de Mars 25, 7000 Mons, Belgium.
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7
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Rifaie-Graham O, Hua X, Bruns N, Balog S. The Kinetics of β-Hematin Crystallization Measured by Depolarized Light Scattering. Small 2018; 14:e1802295. [PMID: 30176111 DOI: 10.1002/smll.201802295] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 08/05/2018] [Indexed: 06/08/2023]
Abstract
Malaria is caused by Plasmodium sp. parasites transmitted by infected female Anopheles sp. mosquitoes. The survival of the parasites in the host relies on detoxifying free heme by biocrystallization into insoluble crystals called hemozoin. This mechanism of self-preservation is targeted by a certain class of antimalarial drugs, which are screened and selected based on their capacity to inhibit the formation of hemozoin crystals. Therefore, experimental techniques capable of accurately characterizing the kinetics of crystal formation are valuable. Relying on the optical anisotropy of hemozoin, the kinetics of β-hematin crystal formation through the statistical analysis of photon counts of dynamic depolarized light scattering (DDLS), in the absence and presence of an antimalarial drug (chloroquine, CQ), is described. It is found that CQ has an impact on both the nucleation and growth of the crystals.
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Affiliation(s)
- Omar Rifaie-Graham
- Adolphe Merkle Institute, University of Fribourg, Chemin des, Verdiers 4,1700, Fribourg, Switzerland
| | - Xiao Hua
- Adolphe Merkle Institute, University of Fribourg, Chemin des, Verdiers 4,1700, Fribourg, Switzerland
| | - Nico Bruns
- Adolphe Merkle Institute, University of Fribourg, Chemin des, Verdiers 4,1700, Fribourg, Switzerland
| | - Sandor Balog
- Adolphe Merkle Institute, University of Fribourg, Chemin des, Verdiers 4,1700, Fribourg, Switzerland
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8
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Kondaparla S, Manhas A, Dola VR, Srivastava K, Puri SK, Katti SB. Design, synthesis and antiplasmodial activity of novel imidazole derivatives based on 7-chloro-4-aminoquinoline. Bioorg Chem 2018; 80:204-211. [PMID: 29940342 DOI: 10.1016/j.bioorg.2018.06.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 06/03/2018] [Accepted: 06/04/2018] [Indexed: 10/14/2022]
Abstract
A series of short chain 4-aminoquinoline-imidazole derivatives have been synthesized in one pot two step multicomponent reaction using van leusen standard protocol. The diethylamine function of chloroquine is replaced by substituted imidazole derivatives containing tertiary terminal nitrogen. All the synthesized compounds were screened against the chloroquine sensitive (3D7) and chloroquine resistant (K1) strains of Plasmodium falciparum. Some of the compounds (6, 8, 9 and 17) in the series exhibited comparable activity to CQ against K1 strain of P. falciparum. All the compounds displayed resistance factor between 0.09 and 4.57 as against 51 for CQ. Further, these analogues were found to form a strong complex with hematin and inhibit the β-hematin formation, therefore these compounds act via heme polymerization target.
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Affiliation(s)
- Srinivasarao Kondaparla
- Medicinal & Process Chemistry Division, CSIR-Central Drug Research Institute Sector-10, Jankipuram Extension, Sitapur Road, Lucknow 226031, India.
| | - Ashan Manhas
- Parasitology Division, CSIR-Central Drug Research Institute, Sector-10, Jankipuram Extension, Sitapur Road, Lucknow 226031, India
| | - Vasantha Rao Dola
- Medicinal & Process Chemistry Division, CSIR-Central Drug Research Institute Sector-10, Jankipuram Extension, Sitapur Road, Lucknow 226031, India
| | - Kumkum Srivastava
- Parasitology Division, CSIR-Central Drug Research Institute, Sector-10, Jankipuram Extension, Sitapur Road, Lucknow 226031, India
| | - Sunil K Puri
- Parasitology Division, CSIR-Central Drug Research Institute, Sector-10, Jankipuram Extension, Sitapur Road, Lucknow 226031, India
| | - S B Katti
- Medicinal & Process Chemistry Division, CSIR-Central Drug Research Institute Sector-10, Jankipuram Extension, Sitapur Road, Lucknow 226031, India
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9
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Kumar G, Tanwar O, Kumar J, Akhter M, Sharma S, Pillai CR, Alam MM, Zama MS. Pyrazole-pyrazoline as promising novel antimalarial agents: A mechanistic study. Eur J Med Chem 2018; 149:139-147. [PMID: 29499486 DOI: 10.1016/j.ejmech.2018.01.082] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Revised: 01/17/2018] [Accepted: 01/25/2018] [Indexed: 11/19/2022]
Abstract
A series of pyrazole-pyrazoline substituted with benzenesulfonamide were synthesized and evaluated for their antimalarial activity in vitro and in vivo. The compounds were active against both chloroquine (CQ) sensitive (3D7) and CQ resistant (RKL-9) strains of Plasmodium falciparum. Seven compounds (7e, 7i, 7j, 7l, 7m, 7o and 7p) exhibiting EC50 less than 2 μM. A mechanistic study of compound 7o revealed that these compound act through the inhibition of β-hematin. The study indicated that these compounds can serve as lead compounds for further development of potent antimalarial drugs.
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Affiliation(s)
- Gautam Kumar
- Drug Design and Medicinal Chemistry Lab, Department of Pharmaceutical Chemistry, School of Pharmaceutical Education and Research, Jamia Hamdard, New Delhi, India
| | - Omprakash Tanwar
- Drug Design and Medicinal Chemistry Lab, Department of Pharmaceutical Chemistry, School of Pharmaceutical Education and Research, Jamia Hamdard, New Delhi, India
| | - Jitender Kumar
- Drug Design and Medicinal Chemistry Lab, Department of Pharmaceutical Chemistry, School of Pharmaceutical Education and Research, Jamia Hamdard, New Delhi, India
| | - Mymoona Akhter
- Drug Design and Medicinal Chemistry Lab, Department of Pharmaceutical Chemistry, School of Pharmaceutical Education and Research, Jamia Hamdard, New Delhi, India.
| | - Supriya Sharma
- National Institute of Malaria Research (ICMR), Sector 8, Dwarka, New Delhi, 110077, India
| | - C R Pillai
- National Institute of Malaria Research (ICMR), Sector 8, Dwarka, New Delhi, 110077, India
| | - Md Mumtaz Alam
- Drug Design and Medicinal Chemistry Lab, Department of Pharmaceutical Chemistry, School of Pharmaceutical Education and Research, Jamia Hamdard, New Delhi, India
| | - M S Zama
- Drug Design and Medicinal Chemistry Lab, Department of Pharmaceutical Chemistry, School of Pharmaceutical Education and Research, Jamia Hamdard, New Delhi, India
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10
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Fitzroy SM, Gildenhuys J, Olivier T, Tshililo NO, Kuter D, de Villiers KA. The Effects of Quinoline and Non-Quinoline Inhibitors on the Kinetics of Lipid-Mediated β-Hematin Crystallization. Langmuir 2017; 33:7529-7537. [PMID: 28689414 PMCID: PMC5709178 DOI: 10.1021/acs.langmuir.7b01132] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The throughput of a biomimetic lipid-mediated assay used to investigate the effects of inhibitors on the kinetics of β-hematin formation has been optimized through the use of 24-well microplates. The rate constant for β-hematin formation mediated by monopalmitoyl-rac-glycerol was reduced from 0.17 ± 0.04 min-1 previously measured in Falcon tubes to 0.019 ± 0.002 min-1 in the optimized assay. While this necessitated longer incubation times, transferring aliquots from multiple 24-well plates to a single 96-well plate for final absorbance measurements actually improved the overall turnaround time per inhibitor. This assay has been applied to investigate the effects of four clinically relevant antimalarial drugs (chloroquine, amodiaquine, quinidine, and quinine) as well as several short-chain 4-aminoquinoline derivatives and non-quinoline (benzamide) compounds on the kinetics of β-hematin formation. The adsorption strength of these inhibitors to crystalline β-hematin (Kads) was quantified using a theoretical kinetic model that is based on the Avrami equation and the Langmuir isotherm. Statistically significant linear correlations between lipid-mediated β-hematin inhibitory activity and Kads values for quinoline (r2 = 0.76, P-value = 0.0046) and non-quinoline compounds (r2 = 0.99, P-stat = 0.0006), as well as between parasite inhibitory activity (D10) and Kads values for quinoline antimalarial drugs and short-chain chloroquine derivatives (r2 = 0.64, P-value = 0.0098), provide a strong indication that drug action involves adsorption to the surface of β-hematin crystals. Independent support in this regard is provided by experiments that spectrophotometrically monitor the direct adsorption of antimalarial drugs to preformed β-hematin.
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11
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Okombo J, Singh K, Mayoka G, Ndubi F, Barnard L, Njogu PM, Njoroge M, Gibhard L, Brunschwig C, Vargas M, Keiser J, Egan TJ, Chibale K. Antischistosomal Activity of Pyrido[1,2-a]benzimidazole Derivatives and Correlation with Inhibition of β-Hematin Formation. ACS Infect Dis 2017; 3:411-420. [PMID: 28440625 DOI: 10.1021/acsinfecdis.6b00205] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The extensive use of praziquantel against schistosomiasis raises concerns about drug resistance. New therapeutic alternatives targeting critical pathways within the parasite are therefore urgently needed. Hemozoin formation in Schistosoma presents one such target. We assessed the in vitro antischistosomal activity of pyrido[1,2-a]benzimidazoles (PBIs) and investigated correlations with their ability to inhibit β-hematin formation. We further evaluated the in vivo efficacy of representative compounds in experimental mice and conducted pharmacokinetic analysis on the most potent. At 10 μM, 48/57 compounds resulted in >70% mortality of newly transformed schistosomula, whereas 37 of these maintained >60% mortality of adult S. mansoni. No correlations were observed between β-hematin inhibitory and antischistosomal activities against both larval and adult parasites, suggesting possible presence of other target(s) or a mode of inhibition of crystal formation that is not adequately modeled by the assay. The most active compound in vivo showed 58.7 and 61.3% total and female worm burden reduction, respectively. Pharmacokinetic analysis suggested solubility-limited absorption and high hepatic clearance as possible contributors to the modest efficacy despite good in vitro activity. The PBIs evaluated in this report thus merit further optimization to improve their efficacy and to elucidate their possible mode of action.
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Affiliation(s)
- John Okombo
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Kawaljit Singh
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Godfrey Mayoka
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Ferdinand Ndubi
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Linley Barnard
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Peter M. Njogu
- Department of Pharmaceutical Chemistry, University of Nairobi, P.O. Box 19676, Nairobi 00202, Kenya
| | - Mathew Njoroge
- Drug Discovery and Development Centre (H3D),
Division of Clinical Pharmacology, Department of Medicine, University of Cape Town, Observatory 7925, South Africa
| | - Liezl Gibhard
- Drug Discovery and Development Centre (H3D),
Division of Clinical Pharmacology, Department of Medicine, University of Cape Town, Observatory 7925, South Africa
| | - Christel Brunschwig
- Drug Discovery and Development Centre (H3D),
Division of Clinical Pharmacology, Department of Medicine, University of Cape Town, Observatory 7925, South Africa
| | - Mireille Vargas
- Department of Medical Parasitology and
Infection Biology, Swiss Tropical and Public Health Institute, 4051 Basel, Switzerland
- University of Basel, 4003 Basel, Switzerland
| | - Jennifer Keiser
- Department of Medical Parasitology and
Infection Biology, Swiss Tropical and Public Health Institute, 4051 Basel, Switzerland
- University of Basel, 4003 Basel, Switzerland
| | - Timothy J. Egan
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Kelly Chibale
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
- South African Medical Research Council,
Drug Discovery and Development Research Unit, University of Cape Town, Rondebosch 7701, South Africa
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Rondebosch 7701, South Africa
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12
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Jacobs L, de Kock C, de Villiers KA, Smith PJ, Smith VJ, van Otterlo WAL, Blackie MAL. Design, Synthesis, and Evaluation of Novel Ferroquine and Phenylequine Analogues as Potential Antiplasmodial Agents. ChemMedChem 2015; 10:2099-110. [PMID: 26447782 DOI: 10.1002/cmdc.201500349] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Indexed: 11/11/2022]
Abstract
7-Chloroquinoline-based antimalarial drugs are effective in the inhibition of hemozoin formation in the food vacuole of the Plasmodium parasite, the causative agent of malaria. We synthesized five series of ferroquine (FQ) and phenylequine (PQ) derivatives, which display good in vitro efficacy toward both the chloroquine-sensitive (CQS) NF54 (IC50 : 4.2 nm) and chloroquine-resistant (CQR) Dd2 (IC50 : 33.7 nm) strains of P. falciparum. Several compounds were found to have good inhibitory activity against β-hematin formation in an NP-40 detergent assay, with IC50 values ranging between 10.4 and 19.2 μm.
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Affiliation(s)
- Leon Jacobs
- Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | - Carmen de Kock
- Department of Pharmacology, University of Cape Town, Private Bag X2, Rondebosch, Cape Town, 7700, South Africa
| | - Katherine A de Villiers
- Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | - Peter J Smith
- Department of Pharmacology, University of Cape Town, Private Bag X2, Rondebosch, Cape Town, 7700, South Africa
| | - Vincent J Smith
- Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | - Willem A L van Otterlo
- Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | - Margaret A L Blackie
- Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa.
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13
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Fong KY, Sandlin RD, Wright DW. Identification of β-hematin inhibitors in the MMV Malaria Box. Int J Parasitol Drugs Drug Resist 2015; 5:84-91. [PMID: 26150923 PMCID: PMC4486462 DOI: 10.1016/j.ijpddr.2015.05.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 05/15/2015] [Accepted: 05/19/2015] [Indexed: 11/22/2022]
Abstract
The Malaria Box, assembled by the Medicines for Malaria Venture, is a set of 400 structurally diverse, commercially available compounds with demonstrated activity against blood-stage Plasmodium falciparum. The compounds are a representative subset of the 20,000 in vitro antimalarials identified from the high-throughput screening efforts of St. Jude Children's Research Hospital (TN, USA), Novartis and GlaxoSmithKline. In addition, a small set of active compounds from commercially available libraries was added to this group, but it has not previously been published. Elucidation of the biochemical pathways on which these compounds act is a major challenge; therefore, access to these compounds has been made available free of charge to the investigator community. Here, the Malaria Box compounds were tested for activity against the formation of β-hematin, a synthetic form of the heme detoxification biomineral, hemozoin. Further, the mechanism of action of these compounds within the malaria parasite was explored. Ten of the Malaria Box compounds demonstrated significant inhibition of β-hematin formation. In this assay, dose–response data revealed IC50 values ranging from 8.7 to 22.7 μM for these hits, each of which is more potent than chloroquine (a known inhibitor of hemozoin formation). The in vitro antimalarial activity of these ten hits was confirmed in cultures of the chloroquine sensitive D6 strain of the parasite resulting in IC50 values of 135–2165 nM, followed by testing in the multidrug resistant strain, C235. Cultures of P. falciparum (D6) were then examined for their heme distribution following treatment with nine of the commercially available confirmed compounds, seven of which disrupted the hemozoin pathway. Ten of 400 Malaria Box compounds were found to be potent β-hematin inhibitors. We confirmed similar in vitro antimalarial activity to results from previous screens. 7 of the 9 commercially available hits were validated hemozoin inhibitors in culture.
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Affiliation(s)
- Kim Y Fong
- Department of Chemistry, Vanderbilt University, Station B 351822, Nashville, TN 37235, USA
| | - Rebecca D Sandlin
- Department of Chemistry, Vanderbilt University, Station B 351822, Nashville, TN 37235, USA
| | - David W Wright
- Department of Chemistry, Vanderbilt University, Station B 351822, Nashville, TN 37235, USA
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14
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Lanfranchi DA, Cesar-Rodo E, Bertrand B, Huang HH, Day L, Johann L, Elhabiri M, Becker K, Williams DL, Davioud-Charvet E. Synthesis and biological evaluation of 1,4-naphthoquinones and quinoline-5,8-diones as antimalarial and schistosomicidal agents. Org Biomol Chem 2012; 10:6375-87. [PMID: 22777178 PMCID: PMC3423093 DOI: 10.1039/c2ob25812a] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Improving the solubility of polysubstituted 1,4-naphthoquinone derivatives was achieved by introducing nitrogen in two different positions of the naphthoquinone core, at C-5 and at C-8 of menadione through a two-step, straightforward synthesis based on the regioselective hetero-Diels-Alder reaction. The antimalarial and the antischistosomal activities of these polysubstituted aza-1,4-naphthoquinone derivatives were evaluated and led to the selection of distinct compounds for antimalarial versus antischistosomal action. The Ag(II)-assisted oxidative radical decarboxylation of the phenyl acetic acids using AgNO(3) and ammonium peroxodisulfate was modified to generate the 3-picolinyl-menadione with improved pharmacokinetic parameters, high antimalarial effects and capacity to inhibit the formation of β-hematin.
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Affiliation(s)
- Don Antoine Lanfranchi
- European School of Chemistry, Polymers and Materials (ECPM) University of Strasbourg, UMR CNRS 7509, 25 Rue Becquerel, F-67087 Strasbourg, France. Fax: +33 (0)3 68 85 27 42; Tel: +33 3 68 85 26 20
| | - Elena Cesar-Rodo
- European School of Chemistry, Polymers and Materials (ECPM) University of Strasbourg, UMR CNRS 7509, 25 Rue Becquerel, F-67087 Strasbourg, France. Fax: +33 (0)3 68 85 27 42; Tel: +33 3 68 85 26 20
| | - Benoît Bertrand
- European School of Chemistry, Polymers and Materials (ECPM) University of Strasbourg, UMR CNRS 7509, 25 Rue Becquerel, F-67087 Strasbourg, France. Fax: +33 (0)3 68 85 27 42; Tel: +33 3 68 85 26 20
| | - Hsin-Hung Huang
- Department of Immunology/Microbiology, Rush University Medical Center, 1735 West Harrison Street, Chicago, IL 60612, USA
| | - Latasha Day
- Department of Immunology/Microbiology, Rush University Medical Center, 1735 West Harrison Street, Chicago, IL 60612, USA
| | - Laure Johann
- European School of Chemistry, Polymers and Materials (ECPM) University of Strasbourg, UMR CNRS 7509, 25 Rue Becquerel, F-67087 Strasbourg, France. Fax: +33 (0)3 68 85 27 42; Tel: +33 3 68 85 26 20
| | - Mourad Elhabiri
- European School of Chemistry, Polymers and Materials (ECPM) University of Strasbourg, UMR CNRS 7509, 25 Rue Becquerel, F-67087 Strasbourg, France. Fax: +33 (0)3 68 85 27 42; Tel: +33 3 68 85 26 20
| | - Katja Becker
- Interdisciplinary Research Center, Nutritional Biochemistry, Justus Liebig University Giessen, Heinrich-Buff-Ring 26–32, D-35392 Giessen, Germany
| | - David L. Williams
- Department of Immunology/Microbiology, Rush University Medical Center, 1735 West Harrison Street, Chicago, IL 60612, USA
| | - Elisabeth Davioud-Charvet
- European School of Chemistry, Polymers and Materials (ECPM) University of Strasbourg, UMR CNRS 7509, 25 Rue Becquerel, F-67087 Strasbourg, France. Fax: +33 (0)3 68 85 27 42; Tel: +33 3 68 85 26 20
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15
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Abstract
Malaria affects over 200 million individuals annually, resulting in 800,000 fatalities. Current tests use blood smears and can only detect the disease when 0.1-1% of blood cells are infected. We are investigating the use of photoacoustic flowmetry to sense as few as one infected cell among 10 million or more normal blood cells, thus diagnosing infection before patients become symptomatic. Photoacoustic flowmetry is similar to conventional flow cytometry, except that rare cells are targeted by nanosecond laser pulses to induce ultrasonic responses. This system has been used to detect single melanoma cells in 10 ml of blood. Our objective is to apply photoacoustic flowmetry to detection of the malaria pigment hemozoin, which is a byproduct of parasite-digested hemoglobin in the blood. However, hemozoin is difficult to purify in quantities greater than a milligram, so a synthetic analog, known as β-hematin was derived from porcine haemin. The specific purpose of this study is to establish the efficacy of using β-hematin, rather than hemozoin, for photoacoustic measurements. We characterized β-hematin using UV-vis spectroscopy, TEM, and FTIR, then tested the effects of laser irradiation on the synthetic product. We finally determined its absorption spectrum using photoacoustic excitation. UV-vis spectroscopy verified that β-hematin was distinctly different from its precursor. TEM analysis confirmed its previously established nanorod shape, and comparison of the FTIR results with published spectroscopy data showed that our product had the distinctive absorbance peaks at 1661 and 1206 cm(-1). Also, our research indicated that prolonged irradiation dramatically alters the physical and optical properties of the β-hematin, resulting in increased absorption at shorter wavelengths. Nevertheless, the photoacoustic absorption spectrum mimicked that generated by UV-vis spectroscopy, which confirms the accuracy of the photoacoustic method and strongly suggests that photoacoustic flowmetry may be used as a tool for diagnosis of malaria infection.
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Affiliation(s)
- Edward B. Samson
- Department of Biological Engineering, University of Missouri-Columbia, Columbia, Missouri, 65211, USA
- Christopher S. Bond Life Sciences Center, University of Missouri-Columbia, Columbia, Missouri, 65211, USA
| | - Benjamin S. Goldschmidt
- Department of Biological Engineering, University of Missouri-Columbia, Columbia, Missouri, 65211, USA
- Christopher S. Bond Life Sciences Center, University of Missouri-Columbia, Columbia, Missouri, 65211, USA
| | - Paul J. D. Whiteside
- Department of Biological Engineering, University of Missouri-Columbia, Columbia, Missouri, 65211, USA
- Christopher S. Bond Life Sciences Center, University of Missouri-Columbia, Columbia, Missouri, 65211, USA
| | - Amanda S. M. Sudduth
- Department of Biological Engineering, University of Missouri-Columbia, Columbia, Missouri, 65211, USA
- Christopher S. Bond Life Sciences Center, University of Missouri-Columbia, Columbia, Missouri, 65211, USA
| | - John R. Custer
- Department of Biological Engineering, University of Missouri-Columbia, Columbia, Missouri, 65211, USA
- Christopher S. Bond Life Sciences Center, University of Missouri-Columbia, Columbia, Missouri, 65211, USA
| | - Brenda Beerntsen
- Department of Animal Sciences, University of Missouri-Columbia, Columbia, Missouri, 65211, USA
| | - John A. Viator
- Department of Biological Engineering, University of Missouri-Columbia, Columbia, Missouri, 65211, USA
- Christopher S. Bond Life Sciences Center, University of Missouri-Columbia, Columbia, Missouri, 65211, USA
- Department of Dermatology, University of Missouri-Columbia, Columbia, Missouri, 65211, USA
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16
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Nhien NTT, Huy NT, Uyen DT, Deharo E, Hoa PTL, Hirayama K, Harada S, Kamei K. Effect of Inducers, Incubation Time and Heme Concentration on IC(50) Value Variation in Anti-heme Crystallization Assay. Trop Med Health 2012; 39:119-26. [PMID: 22438701 PMCID: PMC3289280 DOI: 10.2149/tmh.2011-29] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Accepted: 10/24/2011] [Indexed: 11/11/2022] Open
Abstract
Heme detoxification through crystallization into hemozoin has been suggested as a good target for the development of screening assays for new antimalarials. However, comparisons among the data obtained from different experiments are difficult, and the IC50 values (the concentrations of drug that are required to inhibit 50% of hemozoin formation) for the same drug vary widely. We studied the effects of changes in heme concentration (precursor of β-hematin), incubation time and three inducers (SDS, Tween 20 and linoleic acid) on the IC50 of some antimalarials (chloroquine, quinine, amodiaquine, and clotrimazole). The results showed that increasing both inducer concentration and incubation time raised the IC50 of selected antimalarials. Any change in those factors caused the IC50 value to vary. Standardization of assay conditions is, therefore, necessary to increase reproducibility and reduce discrepancies in assay performance. Considering all of the variables, the best choice of inducers is in the order of SDS > Tween 20 > linoleic acid.
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Affiliation(s)
- Nguyen Thanh Thuy Nhien
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
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Johann L, Lanfranchi DA, Davioud-Charvet E, Elhabiri M. A physico-biochemical study on potential redox-cyclers as antimalarial and anti-schistosomal drugs. Curr Pharm Des 2012; 18:3539-66. [PMID: 22607146 PMCID: PMC3711147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 03/12/2012] [Indexed: 05/31/2023]
Abstract
The role of redox enzymes in establishing a microenvironment for parasite development is well characterized. Mimicking human glucose-6-phosphate dehydrogenase and glutathione reductase (GR) deficiencies by redox-cycling compounds thus represents a challenge to the design of new preclinical antiparasitic drug candidates. Schistosomes and malarial parasites feed on hemoglobin. Heme, the toxic prosthetic group of the protein, is not digested and represents a challenge to the redox metabolism of the parasites. Here, we report on old and new redox-cycling compounds--whose antiparasitic activities are related to their interference with (met)hemoglobin degradation and hematin crystallization. Three key-assays allowed probing and differentiating the mechanisms of drug actions. Inhibition of β-hematin was first compared to the heme binding as a possible mode of action. All tested ligands interact with the hematin π-π dimer with K(D) similar to those measured for the major antiparasitic drugs. No correlation between a high affinity for hematin and the capacity to prevent β-hematin formation was however deduced. Inhibition of β-hematin formation is consequently not the result of a single process but results from redox processes following electron transfers from the drugs to iron(III)-containing targets. The third experiment highlighted that several redox-active compounds (in their reduced forms) are able to efficiently reduce methemoglobin to hemoglobin in a GR/NADPH-coupled assay. A correlation between methemoglobin reduction and inhibition of β-hematin was shown, demonstrating that both processes are closely related. The ability of our redox-cyclers to trigger methemoglobin reduction therefore constitutes a critical step to understand the mechanism of action of our drug candidates.
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Affiliation(s)
- Laure Johann
- Laboratoire de Chimie Bioorganique et Médicinale, European School of Chemistry, Polymers and Materials (ECPM), University of Strasbourg and Centre National de la Recherche Scientifique, UMR 7509, 25, rue Becquerel, F-67087 Strasbourg, France
| | - Don Antoine Lanfranchi
- Laboratoire de Chimie Bioorganique et Médicinale, European School of Chemistry, Polymers and Materials (ECPM), University of Strasbourg and Centre National de la Recherche Scientifique, UMR 7509, 25, rue Becquerel, F-67087 Strasbourg, France
| | - Elisabeth Davioud-Charvet
- Laboratoire de Chimie Bioorganique et Médicinale, European School of Chemistry, Polymers and Materials (ECPM), University of Strasbourg and Centre National de la Recherche Scientifique, UMR 7509, 25, rue Becquerel, F-67087 Strasbourg, France
| | - Mourad Elhabiri
- Laboratoire de Chimie Bioorganique et Médicinale, European School of Chemistry, Polymers and Materials (ECPM), University of Strasbourg and Centre National de la Recherche Scientifique, UMR 7509, 25, rue Becquerel, F-67087 Strasbourg, France
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18
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Navarro M, Castro W, Martínez A, Sánchez Delgado RA. The mechanism of antimalarial action of [Au(CQ)(PPh(3))]PF(6): structural effects and increased drug lipophilicity enhance heme aggregation inhibition at lipid/water interfaces. J Inorg Biochem 2011; 105:276-82. [PMID: 21194628 PMCID: PMC3038622 DOI: 10.1016/j.jinorgbio.2010.11.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Revised: 11/03/2010] [Accepted: 11/05/2010] [Indexed: 10/18/2022]
Abstract
The mechanism of antimalarial action of [Au(CQ)(PPh(3))]PF(6) (1), which is active in vitro against CQ-resistant P. falciparum and in vivo against P. berghei, has been investigated in relation to hemozoin formation and DNA as possible important targets. Complex 1 interacts with heme and inhibits β-hematin formation both in aqueous medium and near water/n-octanol interfaces at pH ~5 to a greater extent than chloroquine diphosphate (CQDP) or other known metal-based antimalarial agents; the higher inhibition activity is probably related to the higher lipophilicity observed for 1 through partition coefficient measurements at low pH, with respect to CQDP. The interactions of complex 1 with DNA were explored using spectrophotometric and fluorimetric titrations, circular dichroism spectroscopy, viscosity and melting point studies, as well as electrophoresis and covalent binding assays. The experimental data indicate that complex 1 interacts with DNA predominantly by intercalation and electrostatic association of the CQ moiety, similarly to free CQDP, while no covalent metal-DNA binding seems to take place. The most likely antimalarial mechanism for complex 1 is thus heme aggregation inhibition; the high activities observed against resistant parasites are probably due to the structural modification of CQ introduced by the presence of the gold-triphenylphosphine fragment, together with the enhanced lipophilic character.
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Affiliation(s)
- Maribel Navarro
- Laboratorio de Química Bioinorgánica, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Carretera Panamericana Km.11, Altos de Pipe. Caracas 1020-A, Venezuela.
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