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Mujawar T, Sevelda P, Madea D, Klán P, Švenda J. A Platform for the Synthesis of Oxidation Products of Bilirubin. J Am Chem Soc 2024; 146:1603-1611. [PMID: 38165253 PMCID: PMC10797625 DOI: 10.1021/jacs.3c11778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 11/30/2023] [Accepted: 12/06/2023] [Indexed: 01/03/2024]
Abstract
Bilirubin is the principal product of heme catabolism. High concentrations of the pigment are neurotoxic, yet slightly elevated levels are beneficial. Being a potent antioxidant, oxidative transformations of bilirubin occur in vivo and lead to various oxidized fragments. The mechanisms of their formation, intrinsic biological activities, and potential roles in human pathophysiology are poorly understood. Degradation methods have been used to obtain samples of bilirubin oxidation products for research. Here, we report a complementary, fully synthetic method of preparation. Our strategy leverages repeating substitution patterns in the parent tetracyclic pigment. Functionalized ready-to-couple γ-lactone, γ-lactam, and pyrrole monocyclic building blocks were designed and efficiently synthesized. Subsequent modular combinations, supported by metal-catalyzed borylation and cross-coupling chemistries, translated into the concise assembly of the structurally diverse bilirubin oxidation products (BOXes, propentdyopents, and biopyrrins). The discovery of a new photoisomer of biopyrrin A named lumipyrrin is reported. Synthetic bilirubin oxidation products made available in sufficient purity and quantity will support future in vitro and in vivo investigations.
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Affiliation(s)
- Taufiqueahmed Mujawar
- Department
of Chemistry, Faculty of Science, Masaryk
University, Kamenice 5, Brno 625 00, Czech Republic
| | - Petr Sevelda
- Department
of Chemistry, Faculty of Science, Masaryk
University, Kamenice 5, Brno 625 00, Czech Republic
| | - Dominik Madea
- Department
of Chemistry, Faculty of Science, Masaryk
University, Kamenice 5, Brno 625 00, Czech Republic
- RECETOX,
Faculty of Science, Masaryk University, Kamenice 5, Brno 625 00, Czech Republic
| | - Petr Klán
- Department
of Chemistry, Faculty of Science, Masaryk
University, Kamenice 5, Brno 625 00, Czech Republic
- RECETOX,
Faculty of Science, Masaryk University, Kamenice 5, Brno 625 00, Czech Republic
| | - Jakub Švenda
- Department
of Chemistry, Faculty of Science, Masaryk
University, Kamenice 5, Brno 625 00, Czech Republic
- International
Clinical Research Center, St. Anne’s
University Hospital, Pekařská 53, Brno 656 91, Czech Republic
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2
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Tahoun M, Engeser M, Svolacchia L, Sander PM, Müller CE. Molecular Taphonomy of Heme: Chemical Degradation of Hemin under Presumed Fossilization Conditions. Molecules 2023; 28:4887. [PMID: 37446548 DOI: 10.3390/molecules28134887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 06/16/2023] [Accepted: 06/18/2023] [Indexed: 07/15/2023] Open
Abstract
The metalloporphyrin heme acts as the oxygen-complexing prosthetic group of hemoglobin in blood. Heme has been noted to survive for many millions of years in fossils. Here, we investigate its stability and degradation under various conditions expected to occur during fossilization. Oxidative, reductive, aerobic, and anaerobic conditions were studied at neutral and alkaline pH values. Elevated temperatures were applied to accelerate degradation. High-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) identified four main degradation products. The vinyl residues are oxidized to formyl and further to carboxylate groups. In the presence of air or H2O2, cleavage of the tetrapyrrole ring occurs, and hematinic acid is formed. The highest stability of heme was observed under anaerobic reductive conditions (half-life 9.5 days), while the lowest stability was found in the presence of H2O2 (half-life 1 min). We confirmed that the iron cation plays a crucial role in degradation, since protoporphyrin IX, lacking iron, remained significantly more stable. Under anaerobic, reductive conditions, the above-mentioned degradation products were not observed, suggesting a different degradation pathway. To our knowledge, this is the first molecular taphonomy study on heme, which will be useful for understanding its fate during fossilization.
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Affiliation(s)
- Mariam Tahoun
- PharmaCenter Bonn & Pharmaceutical Institute, Department of Pharmaceutical & Medicinal Chemistry, University of Bonn, An der Immenburg 4, 53121 Bonn, Germany
| | - Marianne Engeser
- Kekulé Institute for Organic Chemistry and Biochemistry, University of Bonn, 53121 Bonn, Germany
| | - Luca Svolacchia
- PharmaCenter Bonn & Pharmaceutical Institute, Department of Pharmaceutical & Medicinal Chemistry, University of Bonn, An der Immenburg 4, 53121 Bonn, Germany
| | - Paul Martin Sander
- Section Paleontology, Institute of Geosciences, University of Bonn, 53115 Bonn, Germany
| | - Christa E Müller
- PharmaCenter Bonn & Pharmaceutical Institute, Department of Pharmaceutical & Medicinal Chemistry, University of Bonn, An der Immenburg 4, 53121 Bonn, Germany
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Tomat E, Curtis CJ, Astashkin AV, Conradie J, Ghosh A. Multicenter interactions and ligand field effects in platinum(II) tripyrrindione radicals. Dalton Trans 2023; 52:6559-6568. [PMID: 37185585 DOI: 10.1039/d3dt00894k] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The tripyrrin-1,14-dione biopyrrin, which shares the scaffold of several naturally occurring heme metabolites, is a redox-active platform for metal coordination. We report the synthesis of square planar platinum(II) tripyrrindiones, in which the biopyrrin binds as a tridentate radical and the fourth coordination position is occupied by either aqua or tert-butyl isocyanide ligands. These complexes are stable through chromatographic purification and exposure to air. Electron paramagnetic resonance (EPR) data and density functional theory (DFT) analysis confirm that the spin density is located predominantly on the tripyrrindione ligand. Pancake bonding in solution between the Pt(II) tripyrrindione radicals leads to the formation of diamagnetic π dimers at low temperatures. The identity of the monodentate ligand (i.e., aqua vs. isocyanide) affects both the thermodynamic parameters of dimerization and the tripyrrindione-based redox processes in these complexes. Isolation and structural characterization of the oxidized complexes revealed stacking of the diamagnetic tripyrrindiones in the solid state as well as a metallophilic Pt(II)-Pt(II) contact in the case of the aqua complex. Overall, the properties of Pt(II) tripyrrindiones, including redox potentials and intermolecular interactions in solution and in the solid state, are modulated through easily accessible changes in the redox state of the biopyrrin ligand or the nature of the monodentate ligand.
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Affiliation(s)
- Elisa Tomat
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721-0041, USA.
| | - Clayton J Curtis
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721-0041, USA.
| | - Andrei V Astashkin
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721-0041, USA.
| | - Jeanet Conradie
- Department of Chemistry, University of the Free State, Bloemfontein 9300, Republic of South Africa
- Department of Chemistry, UiT - The Arctic University of Norway, N-9037 Tromsø, Norway.
| | - Abhik Ghosh
- Department of Chemistry, UiT - The Arctic University of Norway, N-9037 Tromsø, Norway.
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4
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Madea D, Mujawar T, Dvořák A, Pospíšilová K, Muchová L, Čubáková P, Kloz M, Švenda J, Vítek L, Klán P. Photochemistry of ( Z)-Isovinylneoxanthobilirubic Acid Methyl Ester, a Bilirubin Dipyrrinone Subunit: Femtosecond Transient Absorption and Stimulated Raman Emission Spectroscopy. J Org Chem 2022; 87:3089-3103. [PMID: 35130431 DOI: 10.1021/acs.joc.1c02870] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Bilirubin (BR) is an essential metabolite formed by the catabolism of heme. Phototherapy with blue-green light can be applied to reduce high concentrations of BR in blood and is used especially in the neonatal period. In this work, we studied the photochemistry of (Z)-isovinylneoxanthobilirubic acid methyl ester, a dipyrrinone subunit of BR, by steady-state absorption, femtosecond transient absorption, and stimulated Raman spectroscopies. Both the (Z)- and (E)-configurational isomers of isovinylneoxanthobilirubic acid undergo wavelength-dependent and reversible photoisomerization. The isomerization from the excited singlet state is ultrafast (the lifetimes of (Z)- and (E)-isomers were found to be ∼0.9 and 0.1 ps, respectively), and its efficiencies increase with increased photon energy. In addition, we studied sensitized photooxidation of the dipyrrinone subunit by singlet oxygen that leads to the formation of propentdyopents. Biological activities of these compounds, namely, effects on the superoxide production, lipoperoxidation, and tricarboxylic acid cycle metabolism, were also studied. Finally, different photochemical and biological properties of this BR subunit and its structural analogue, (Z)-vinylneoxanthobilirubic acid methyl ester, studied before, are discussed.
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Affiliation(s)
- Dominik Madea
- Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic.,RECETOX, Faculty of Science, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
| | - Taufiqueahmed Mujawar
- Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
| | - Aleš Dvořák
- Institute of Medical Biochemistry and Laboratory Diagnostics, General University Hospital in Prague and 1st Faculty of Medicine, Charles University, Na Bojišti 3, 121 08 Prague 2, Czech Republic
| | - Kateřina Pospíšilová
- Institute of Medical Biochemistry and Laboratory Diagnostics, General University Hospital in Prague and 1st Faculty of Medicine, Charles University, Na Bojišti 3, 121 08 Prague 2, Czech Republic
| | - Lucie Muchová
- Institute of Medical Biochemistry and Laboratory Diagnostics, General University Hospital in Prague and 1st Faculty of Medicine, Charles University, Na Bojišti 3, 121 08 Prague 2, Czech Republic
| | - Petra Čubáková
- Institute of Physics of the Czech Academy of Sciences, ELI Beamlines, Za Radnicí 835, 252 41 Dolní Břežany, Czech Republic.,University of South Bohemia in České Budějovice, Branišovská, 1645/31a, 370 05 České Budějovice, Czech Republic
| | - Miroslav Kloz
- University of South Bohemia in České Budějovice, Branišovská, 1645/31a, 370 05 České Budějovice, Czech Republic
| | - Jakub Švenda
- Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
| | - Libor Vítek
- Institute of Medical Biochemistry and Laboratory Diagnostics, and 4th Department of Internal Medicine, General University Hospital in Prague and 1st Faculty of Medicine, Charles University, Na Bojišti 3, 121 08 Prague 2, Czech Republic
| | - Petr Klán
- Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic.,RECETOX, Faculty of Science, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
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Tomat E, Curtis CJ. Biopyrrin Pigments: From Heme Metabolites to Redox-Active Ligands and Luminescent Radicals. Acc Chem Res 2021; 54:4584-4594. [PMID: 34870973 DOI: 10.1021/acs.accounts.1c00613] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Redox-active ligands in coordination chemistry not only modulate the reactivity of the bound metal center but also serve as electron reservoirs to store redox equivalents. Among many applications in contemporary chemistry, the scope of redox-active ligands in biology is exemplified by the porphyrin radicals in the catalytic cycles of multiple heme enzymes (e.g., cytochrome P450, catalase) and the chlorophyll radicals in photosynthetic systems. This Account reviews the discovery of two redox-active ligands inspired by oligopyrrolic fragments found in biological settings as products of heme metabolism.Linear oligopyrroles, in which pyrrole heterocycles are linked by methylene or methine bridges, are ubiquitous in nature as part of the complex, multistep biosynthesis and degradation of hemes and chlorophylls. Bile pigments, such as biliverdin and bilirubin, are common and well-studied tetrapyrroles with characteristic pyrrolin-2-one rings at both terminal positions. The coordination chemistry of these open-chain pigments is less developed than that of porphyrins and other macrocyclic oligopyrroles; nevertheless, complexes of biliverdin and its synthetic analogs have been reported, along with fluorescent zinc complexes of phytobilins employed as bioanalytical tools. Notably, linear conjugated tetrapyrroles inherit from porphyrins the ability to stabilize unpaired electrons within their π system. The isolated complexes, however, present helical structures and generally limited stability.Smaller biopyrrins, which feature three or two pyrrole rings and the characteristic oxidized termini, have been known for several decades following their initial isolation as urinary pigments and heme metabolites. Although their coordination chemistry has remained largely unexplored, these compounds are structurally similar to the well-established tripyrrin and dipyrrin ligands employed in a broad variety of metal complexes. In this context, our study of the coordination chemistry of tripyrrin-1,14-dione and dipyrrin-1,9-dione was motivated by the potential to retain on these compact, versatile platforms the reversible ligand-based redox chemistry of larger tetrapyrrolic systems.The tripyrrindione ligand coordinates several divalent transition metals (i.e., Pd(II), Ni(II) Cu(II), Zn(II)) to form neutral complexes in which an unpaired electron is delocalized over the conjugated π system. These compounds, which are stable at room temperature and exposed to air, undergo reversible one-electron processes to access different redox states of the ligand system without affecting the oxidation state and coordination geometry of the metal center. We also characterized ligand-based radicals on the dipyrrindione platform in both homoleptic and heteroleptic complexes. In addition, this study documented noncovalent interactions (e.g., interligand hydrogen bonds with the pyrrolinone carbonyls, π-stacking of ligand-centered radicals) as important aspects of this coordination chemistry. Furthermore, the fluorescence of the zinc-bound tripyrrindione radical and the redox-switchable emission of a dipyrrindione BODIPY-type fluorophore showcased the potential interplay of redox chemistry and luminescence in these compounds. Supported by computational analyses, the portfolio of properties revealed by this investigation takes the tripyrrindione and dipyrrindione motifs of heme metabolites to the field of redox-active ligands, where they are positioned to offer new opportunities for catalysis, sensing, supramolecular systems, and functional materials.
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Affiliation(s)
- Elisa Tomat
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721-0041, United States
| | - Clayton J. Curtis
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721-0041, United States
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Curtis CJ, Astashkin AV, Conradie J, Ghosh A, Tomat E. Ligand-Centered Triplet Diradical Supported by a Binuclear Palladium(II) Dipyrrindione. Inorg Chem 2021; 60:12457-12466. [PMID: 34347474 PMCID: PMC8389801 DOI: 10.1021/acs.inorgchem.1c01691] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Oligopyrroles
form
a versatile class of redox-active ligands and
electron reservoirs. Although the stabilization of radicals within
oligopyrrolic π systems is more common for macrocyclic ligands,
bidentate dipyrrindiones are emerging as compact platforms for one-electron
redox chemistry in transition-metal complexes. We report the synthesis
of a bis(aqua) palladium(II) dipyrrindione complex and its deprotonation-driven
dimerization to form a hydroxo-bridged binuclear complex in the presence
of water or triethylamine. Electrochemical, spectroelectrochemical,
and computational analyses of the binuclear complex indicate the accessibility
of two quasi-reversible ligand-centered reduction processes. The product
of a two-electron chemical reduction by cobaltocene was isolated and
characterized. In the solid state, this cobaltocenium salt features
a folded dianionic complex that maintains the hydroxo bridges between
the divalent palladium centers. X-band and Q-band EPR spectroscopic
experiments and DFT computational analysis allow assignment of the
dianionic species as a diradical with spin density almost entirely
located on the two dipyrrindione ligands. As established from the
EPR temperature dependence, the associated exchange coupling is weak
and antiferromagnetic (J ≈ −2.5 K),
which results in a predominantly triplet state at the temperatures
at which the measurements have been performed. The coordination and redox chemistry of the dipyrrindione
scaffold, which is found in several heme metabolites, is investigated
in heteroleptic palladium(II) complexes. The bis(aqua) complex undergoes
a deprotonation-driven dimerization to form a hydroxo-bridged binuclear
species. Crystallographic, electrochemical, and spectroscopic data,
as well as computational analysis, demonstrate that a two-electron
reduction of the binuclear complex leads to a diradical dianion with
spin density delocalized over the two dipyrrindione ligands.
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Affiliation(s)
- Clayton J Curtis
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 East University Blvd., Tucson, Arizona 85721, United States
| | - Andrei V Astashkin
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 East University Blvd., Tucson, Arizona 85721, United States
| | - Jeanet Conradie
- Department of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein 9300, Republic of South Africa.,Department of Chemistry, UiT - The Arctic University of Norway, N-9037 Tromsø, Norway
| | - Abhik Ghosh
- Department of Chemistry, UiT - The Arctic University of Norway, N-9037 Tromsø, Norway
| | - Elisa Tomat
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 East University Blvd., Tucson, Arizona 85721, United States
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