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Reddy GM, Sravya G, Yuvaraja G, Camilo A, Zyryanov GV, Garcia JR. Highly functionalized pyranopyrazoles: synthesis, antimicrobial activity, simulation studies and their structure activity relationships (SARs). RESEARCH ON CHEMICAL INTERMEDIATES 2018. [DOI: 10.1007/s11164-018-3569-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Misra SK, Ghoshal G, Gartia MR, Wu Z, De AK, Ye M, Bromfield CR, Williams EM, Singh K, Tangella KV, Rund L, Schulten K, Schook LB, Ray PS, Burdette EC, Pan D. Trimodal Therapy: Combining Hyperthermia with Repurposed Bexarotene and Ultrasound for Treating Liver Cancer. ACS NANO 2015; 9:10695-10718. [PMID: 26435333 PMCID: PMC4820022 DOI: 10.1021/acsnano.5b05974] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Repurposing of existing cancer drugs to overcome their physical limitations, such as insolubility, represents an attractive strategy to achieve enhanced therapeutic efficacy and broaden the range of clinical applications. Such an approach also promises to offer substantial cost savings in drug development efforts. Here we repurposed FDA-approved topical agent bexarotene (Targretin), currently in limited use for cutaneous manifestations of T-cell lymphomas, and re-engineer it for use in solid tumor applications by forming self-assembling nanobubbles. Physico-chemical characterization studies of the novel prodrug nanobubbles demonstrated their stability, enhanced target cell internalization capability, and highly controlled release profile in response to application of focused ultrasound energy. Using an in vitro model of hepatocellular carcinoma and an in vivo large animal model of liver ablation, we demonstrate the effectiveness of bexarotene prodrug nanobubbles when used in conjunction with catheter-based ultrasound, thereby highlighting the therapeutic promise of this trimodal approach.
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Affiliation(s)
- Santosh K. Misra
- Department of Bioengineering University of Illinois at Urbana-Champaign, USA
| | - Goutam Ghoshal
- Acoustic Med System, 208 Burwash Ave, Savoy, Illinois, USA
| | - Manas R. Gartia
- Department of Bioengineering University of Illinois at Urbana-Champaign, USA
| | - Zhe Wu
- Center for the Physics of Living Cells, Department of Physics, University of Illinois at Urbana-Champaign, Illinois, USA
| | - Arun K. De
- Department of Animal Sciences, University of Illinois, Champaign-Urbana, Illinois, USA
| | - Mao Ye
- Department of Bioengineering University of Illinois at Urbana-Champaign, USA
| | - Corinne R. Bromfield
- Agricultural Animal Care and Use Program, University of Illinois at Urbana-Champaign, Illinois, USA
| | | | - Kuldeep Singh
- Veterinary Diagnostic Laboratory, University of Illinois, Champaign-Urbana, Illinois, USA
| | | | - Laurie Rund
- Department of Animal Sciences, University of Illinois, Champaign-Urbana, Illinois, USA
| | - Klaus Schulten
- Beckman Institute of Advanced Science and Technology, University of Illinois at Urbana-Champaign, Illinois, USA
| | - Lawrence B. Schook
- Department of Bioengineering University of Illinois at Urbana-Champaign, USA
- Department of Animal Sciences, University of Illinois, Champaign-Urbana, Illinois, USA
| | - Partha S. Ray
- Department of Bioengineering University of Illinois at Urbana-Champaign, USA
- Beckman Institute of Advanced Science and Technology, University of Illinois at Urbana-Champaign, Illinois, USA
| | | | - Dipanjan Pan
- Department of Bioengineering University of Illinois at Urbana-Champaign, USA
- Beckman Institute of Advanced Science and Technology, University of Illinois at Urbana-Champaign, Illinois, USA
- Mills Breast Cancer Institute, Carle Foundation Hospital, 502 N. Busey, Urbana, Illinois, USA
- Department of Materials Science and Engineering, University of Illinois-Urbana Champaign, Illinois, USA
- Corresponding author: (UIUC) and (AMS)
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Tripathi SK, Singh SK. Insights into the structural basis of 3,5-diaminoindazoles as CDK2 inhibitors: prediction of binding modes and potency by QM-MM interaction, MESP and MD simulation. MOLECULAR BIOSYSTEMS 2015; 10:2189-201. [PMID: 24909777 DOI: 10.1039/c4mb00077c] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The novel 3,5-diaminoindazole derivatives are well-known as potent and anti-proliferative cyclin-dependent kinase 2 inhibitors. We report a combined quantum mechanics/molecular mechanics study to determine the protein-ligand interaction energy, and some quantum chemical descriptors to successfully rank these inhibitors. The results in this work show that the QM-MM interaction energy is strongly correlated to the biological activity and can be used as a predictor, which was further validated by Spearman's rank correlation coefficient. An exhaustive analysis of the protein-ligand structures obtained from molecular dynamics simulations shows specific interactions within the active site. Furthermore, the docking study was supported by electronic property analysis using density functional theory at the B3LYP/3-21*G level. The results obtained from molecular docking and surface analysis shed some insight on steric and electronic complementarities of these molecules to CDK2. Aqueous solvation energy values give an indication of the solubility and can be used as a guide for the pharmacokinetic optimization of these molecules. Furthermore, ADME/T properties calculated are in the desirable range, so these compounds are predicted to be drug like with low toxicity potential. Overall, the approach was successful in the cases considered, and it could be useful for the design of inhibitors in the lead optimization phase of drug discovery against CDK2.
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Affiliation(s)
- Sunil Kumar Tripathi
- Computer Aided Drug Designing and Molecular Modeling Lab, Department of Bioinformatics, Alagappa University, Karaikudi-630 003, Tamil Nadu, India.
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Chinnasamy S, Nagamani S, Muthusamy K. Zn2+ion of the snake venom metalloproteinase (SVMP) plays a critical role in ligand binding: a molecular dynamics simulation study. RSC Adv 2015. [DOI: 10.1039/c5ra14693c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Snake venom metalloproteinase (SVMP) is one of the major components of snake venom and it is a root causative agent for edema, local tissue damage, inflammation, blood coagulation and hemorrhage during the snake bite.
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Design, synthesis, quantum chemical studies and biological activity evaluation of pyrazole–benzimidazole derivatives as potent Aurora A/B kinase inhibitors. Bioorg Med Chem Lett 2013; 23:3523-30. [DOI: 10.1016/j.bmcl.2013.04.039] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 04/13/2013] [Accepted: 04/16/2013] [Indexed: 11/19/2022]
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Obach RS. Pharmacologically active drug metabolites: impact on drug discovery and pharmacotherapy. Pharmacol Rev 2013; 65:578-640. [PMID: 23406671 DOI: 10.1124/pr.111.005439] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Metabolism represents the most prevalent mechanism for drug clearance. Many drugs are converted to metabolites that can retain the intrinsic affinity of the parent drug for the pharmacological target. Drug metabolism redox reactions such as heteroatom dealkylations, hydroxylations, heteroatom oxygenations, reductions, and dehydrogenations can yield active metabolites, and in rare cases even conjugation reactions can yield an active metabolite. To understand the contribution of an active metabolite to efficacy relative to the contribution of the parent drug, the target affinity, functional activity, plasma protein binding, membrane permeability, and pharmacokinetics of the active metabolite and parent drug must be known. Underlying pharmacokinetic principles and clearance concepts are used to describe the dispositional behavior of metabolites in vivo. A method to rapidly identify active metabolites in drug research is described. Finally, over 100 examples of drugs with active metabolites are discussed with regard to the importance of the metabolite(s) in efficacy and safety.
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Affiliation(s)
- R Scott Obach
- Pfizer Inc., Eastern Point Rd., Groton, CT 06340, USA.
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Noscapinoids with anti-cancer activity against human acute lymphoblastic leukemia cells (CEM): a three dimensional chemical space pharmacophore modeling and electronic feature analysis. J Mol Model 2011; 18:307-18. [DOI: 10.1007/s00894-011-1057-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2011] [Accepted: 03/22/2011] [Indexed: 10/18/2022]
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Tawari NR, Degani MS. Pharmacophore mapping and electronic feature analysis for a series of nitroaromatic compounds with antitubercular activity. J Comput Chem 2010; 31:739-51. [PMID: 19569203 DOI: 10.1002/jcc.21371] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A five point pharmacophore was generated using PHASE for a series of nitroaromatic compounds and their congeners as antitubercular agents. The generated pharmacophore yielded significant 3D-QSAR model with r(2) of 0.890 for a training set of 92 molecules. The model also showed excellent predictive power with correlation coefficient Q(2) of 0.857 for a test set of 31 compounds. The pharmacophore indicated that presence of a nitro group, a piperazine moiety, one aromatic ring feature and two acceptor features are necessary for potent antitubercular activity. The pharmacophore was supported by electronic property analysis using density functional theory (DFT) at B3LYP/3-21*G level. Molecular electrostatic profile of the compounds was consistent with the generated pharmacophore model, particularly appearance of localized negative potential regions near both the oxygen atoms of nitro group extending laterally to the isoxazole ring system/amide bond in the most active compounds. Calculated data further revealed that all active compounds have smaller LUMO energies located over the nitro group, furan ring, and isoxazole ring/amide bond attached to it. Higher negative values of LUMO energies concentrated over the nitro group are indicative of the electron acceptor capacity of the compounds, suggesting that these compounds are prodrugs and must be activated by TB-nitroreductase. The results obtained from this study should aid in efficient design and development of nitroaromatic compounds as antitubercular agents.
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Affiliation(s)
- Nilesh R Tawari
- Department of Pharmaceutical Sciences and Technology, Institute of Chemical Technology, University of Mumbai, Matunga (E), Mumbai 400019, India
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Structural analysis of trypanosomal sirtuin: an insight for selective drug design. Mol Divers 2009; 14:169-78. [DOI: 10.1007/s11030-009-9147-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2008] [Accepted: 03/27/2009] [Indexed: 10/27/2022]
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Kadam RU, Garg D, Roy N. Selective Mapping of Chemical Space for Pseudomonas aeruginosa Deacetylase LpxC Inhibitory Potential. Chem Biol Drug Des 2007; 71:45-56. [DOI: 10.1111/j.1747-0285.2007.00608.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Kadam RU, Garg D, Paul AT, Bhutani KK, Roy N. Evaluation of Proinflammatory Cytokine Pathway Inhibitors for p38 MAPK Inhibitory Potential. J Med Chem 2007; 50:6337-42. [DOI: 10.1021/jm0706923] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Rameshwar U. Kadam
- Centre of Pharmacoinformatics and Department of Natural Products, National Institute of Pharmaceutical Education and Research, Sector 67, S.A.S Nagar-160 062, Punjab, India
| | - Divita Garg
- Centre of Pharmacoinformatics and Department of Natural Products, National Institute of Pharmaceutical Education and Research, Sector 67, S.A.S Nagar-160 062, Punjab, India
| | - Atish T. Paul
- Centre of Pharmacoinformatics and Department of Natural Products, National Institute of Pharmaceutical Education and Research, Sector 67, S.A.S Nagar-160 062, Punjab, India
| | - K. K. Bhutani
- Centre of Pharmacoinformatics and Department of Natural Products, National Institute of Pharmaceutical Education and Research, Sector 67, S.A.S Nagar-160 062, Punjab, India
| | - Nilanjan Roy
- Centre of Pharmacoinformatics and Department of Natural Products, National Institute of Pharmaceutical Education and Research, Sector 67, S.A.S Nagar-160 062, Punjab, India
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Maślankiewicz MJ, Jaworska M, Lodowski P. Competition betweenS-oxidation and nitration in reactions of some β- and γ-quinolinyl sulfides with nitrating mixture. J Heterocycl Chem 2007. [DOI: 10.1002/jhet.5570440518] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Schlitzer M. Malaria Chemotherapeutics Part I: History of Antimalarial Drug Development, Currently Used Therapeutics, and Drugs in Clinical Development. ChemMedChem 2007; 2:944-86. [PMID: 17530725 DOI: 10.1002/cmdc.200600240] [Citation(s) in RCA: 179] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Since ancient times, humankind has had to struggle against the persistent onslaught of pathogenic microorganisms. Nowadays, malaria is still the most important infectious disease worldwide. Considerable success in gaining control over malaria was achieved in the 1950s and 60s through landscaping measures, vector control with the insecticide DDT, and the widespread administration of chloroquine, the most important antimalarial agent ever. In the late 1960s, the final victory over malaria was believed to be within reach. However, the parasites could not be eradicated because they developed resistance against the most widely used and affordable drugs of that time. Today, cases of malaria infections are on the rise and have reached record numbers. This review gives a short description of the malaria disease, briefly addresses the history of antimalarial drug development, and focuses on drugs currently available for malaria therapy. The present knowledge regarding their mode of action and the mechanisms of resistance are explained, as are the attempts made by numerous research groups to overcome the resistance problem within classes of existing drugs and in some novel classes. Finally, this review covers all classes of antimalarials for which at least one drug candidate is in clinical development. Antimalarial agents that are solely in early development stages will be addressed in a separate review.
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Affiliation(s)
- Martin Schlitzer
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35032 Marburg, Germany.
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Kadam RU, Chavan A, Roy N. Pharmacophoric features of Pseudomonas aeruginosa deacetylase LpxC inhibitors: an electronic and structural analysis. Bioorg Med Chem Lett 2006; 17:861-8. [PMID: 17188864 DOI: 10.1016/j.bmcl.2006.11.069] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2006] [Revised: 11/07/2006] [Accepted: 11/24/2006] [Indexed: 10/23/2022]
Abstract
Various electronic properties of structurally diverse synthetic LpxC inhibitors containing oxazoline, aroylserine and thiazoline rings were calculated and correlated with biological activity. These electronic features include the magnitude and locations of 3-dimensional molecular electrostatic potentials, hydrogen bond acceptor/donor density, lowest unoccupied molecular orbital, and highest occupied molecular orbital. Strong correlation of these stereo-electronic properties with LpxC inhibitory potency reveals the potential pharmacophoric features of specific LpxC inhibitors. Thus, these pharmacophoric features of LpxC inhibitors based on electronic and surface analysis could be successfully exploited for designing more potent LpxC inhibitors.
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Affiliation(s)
- Rameshwar U Kadam
- Center of Pharmacoinformatics, National Institute of Pharmaceutical Education and Research, Sector 67, S.A.S. Nagar, Punjab 160 062, India
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Kadam RU, Kiran VM, Roy N. Comparative protein modeling and surface analysis of Leishmania sirtuin: A potential target for antileishmanial drug discovery. Bioorg Med Chem Lett 2006; 16:6013-8. [PMID: 16982188 DOI: 10.1016/j.bmcl.2006.08.128] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Revised: 08/08/2006] [Accepted: 08/30/2006] [Indexed: 11/16/2022]
Abstract
Homology model of Leishmania SIR2 shed new light on the ligand binding features of this enzyme. The molecular electrostatic potentials (MESP), the cavity depth analysis, and LmSIR2-hSIRT2 models' superposition suggested that the nicotinamide binding catalytic domain has several minor but potentially important structural differences. These differences could be exploited for designing antileishmanial compounds.
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Affiliation(s)
- Rameshwar U Kadam
- Centre of Pharmacoinformatics, National Institute of Pharmaceutical Education and Research, Sector 67, S. A. S. Nagar, Punjab 160062, India
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Khedkar SA, Malde AK, Coutinho EC. Comparative protein modeling of methionine S-adenosyltransferase (MAT) enzyme from Mycobacterium tuberculosis: a potential target for antituberculosis drug discovery. J Mol Graph Model 2005; 23:355-66. [PMID: 15670956 DOI: 10.1016/j.jmgm.2004.11.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2004] [Revised: 10/27/2004] [Accepted: 11/03/2004] [Indexed: 11/25/2022]
Abstract
Mycobacterium tuberculosis (Mtb) is a successful pathogen that overcomes the numerous challenges presented by the immune system of the host. In the last 40 years few anti-TB drugs have been developed, while the drug-resistance problem is increasing; there is thus a pressing need to develop new anti-TB drugs active against both the acute and chronic growth phases of the mycobacterium. Methionine S-adenosyltransferase (MAT) is an enzyme involved in the synthesis of S-adenosylmethionine (SAM), a methyl donor essential for mycolipid biosynthesis. As an anti-TB drug target, Mtb-MAT has been well validated. A homology model of MAT has been constructed using the X-ray structures of E. coli MAT (PDB code: 1MXA) and rat MAT (PDB code: 1QM4) as templates, by comparative protein modeling principles. The resulting model has the correct stereochemistry as gauged from the Ramachandran plot and good three-dimensional (3D) structure compatibility as assessed by the Profiles-3D score. The structurally and functionally important residues (active site) of Mtb-MAT have been identified using the E. coli and rat MAT crystal structures and the reported point mutation data. The homology model conserves the topological and active site features of the MAT family of proteins. The differences in the molecular electrostatic potentials (MEP) of Mtb and human MAT provide evidences that selective and specific Mtb-MAT inhibitors can be designed using the homology model, by the structure-based drug design approaches.
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Affiliation(s)
- Santosh A Khedkar
- Department of Pharmaceutical Chemistry, Bombay College of Pharmacy, Kalina, Santacruz (E), Mumbai 400098, India
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Menezes CMS, Sant'Anna CMR, Rodrigues CR, Barreiro EJ. Molecular modeling of novel 1H-pyrazolo[3,4-b]pyridine derivatives designed as isosters of the antimalarial mefloquine. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s0166-1280(01)00677-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Parapini S, Basilico N, Pasini E, Egan TJ, Olliaro P, Taramelli D, Monti D. Standardization of the physicochemical parameters to assess in vitro the beta-hematin inhibitory activity of antimalarial drugs. Exp Parasitol 2000; 96:249-56. [PMID: 11162378 DOI: 10.1006/expr.2000.4583] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intraerythrocytic plasmodia form hemozoin as a detoxification product of hemoglobin-derived heme. An identical substance, beta-hematin (BH), can be obtained in vitro from hematin at acidic pH. Quinoline-antimalarials inhibit BH formation. Standardization of test conditions is essential for studying the interaction of compounds with this process and screening potential inhibitors. A spectrophotometric microassay of heme polymerization inhibitory activity (HPIA) (Basilico et al., Journal of Antimicrobial Chemotherapy 42, 55-60, 1998) previously reported was used to investigate the effect of pH and salt concentration on BH formation. The yield of BH formation decreased with pH. Moreover, under conditions used in the above HPIA assay (18 h, 37 degrees C, pH = 2.7), several salts including chloride and phosphate inhibited the process. Aminoquinoline drugs formulated as salts (chloroquine-phosphate, primaquine-diphosphate), but not chloroquine-base, also inhibited the reaction. Interference by salts was highest at low pH and decreased at higher pH (pH 4). Here, we describe different assay conditions that eliminate these problems (BHIA, beta-hematin inhibitory activity). By replacing hematin with hemin as the porphyrin and NaOH solution with DMSO as solvent, the formation of BH was independent of pH up to pH 5.1. No interference by salts was observed over the pH range 2.7-5.1. Dose-dependent inhibition of BH formation was obtained with chloroquine-base, chloroquine-phosphate, and chloroquine-sulfate at pH 5.1. Primaquine was not inhibitory. The final product, characterized by solubility in DMSO, consists of pure BH by FT-IR spectroscopy. The BHIA assay (hemin in DMSO, acetate buffer pH 5 +/- 0.1, 18 h at 37 degrees C) is designed to screen for those molecules forming pi-pi interactions with hematin and thus inhibiting beta-hematin formation.
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Affiliation(s)
- S Parapini
- Istituto di Microbiologia, Universitá di Milano, Via Pascal 36, 20133 Milano, Italy
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Electrostatic potential profiles may guide cation–pi interaction in antimalarials chloroquine and mefloquine: an ab initio quantum chemical study. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s0166-1280(00)00546-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Karle JM, Bhattacharjee AK. Stereoelectronic features of the cinchona alkaloids determine their differential antimalarial activity. Bioorg Med Chem 1999; 7:1769-74. [PMID: 10530923 DOI: 10.1016/s0968-0896(99)00120-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
For most potent antimalarial activity, the cinchona alkaloids appear to require certain electronic features, particularly a sufficiently acidic hydroxyl proton and an electric field direction pointing from the aliphatic nitrogen atom towards the quinoline ring. These observations are the result of an analysis of molecular electronic properties of eight cinchona alkaloids and an in vivo metabolite calculated using ab initio 3-21G quantum chemical methods in relation to their in vitro IC50 values against chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum parasites. The purpose is to provide a profile of the electronic characteristics necessary for potent antimalarial activity for use in the design of new antimalarial agents and to gain insight into the mechanistic path for antimalarial activity. Distinguishing features of the weakly active epiquinine and epiquinidine include a higher dipole moment, a different direction of the electric field, a greater intrinsic nucleophilicity, lower acidity of the hydroxyl proton, a lesser electron affinity of the lowest unoccupied molecular orbitals, and a higher proton affinity than the active cinchona alkaloids. A moderately potent quinine metabolite possesses some, but not all, of the same electronic features as the most potent cinchona alkaloids. Both the positioning of the hydroxyl and aliphatic amine groups and their electronic features appear to play a crucial role for antimalarial potency of the cinchona alkaloids, most likely by controlling the ability of these groups to form effective intermolecular hydrogen bonds.
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Affiliation(s)
- J M Karle
- Department of Pharmacology, Walter Reed Army Institute of Research, Washington, DC 20307, USA.
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