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Advances in Selenium Catalysts and Antioxidants

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Organic Chemistry".

Deadline for manuscript submissions: 31 May 2024 | Viewed by 8953

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Guest Editor
Department of Chemistry, School of Science, Tokai University, Kanagawa, Japan
Interests: selenium chemistry; protein chemistry
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Selenium (Se) has recently become an important element in a diverse range of research fields, such as biology, biomimetic chemistry, medicinal chemistry, organic synthesis, material science, etc., owing to its characteristic redox behaviors, which are similar but discretely different from those of sister chalcogen elements such as sulfur (S) and tellurium (Te). In this special issue of Molecules, we invite original research articles and reviews on related topics, focusing on the latest advances in selenium catalysts and antioxidants.

Prof. Dr. Michio Iwaoka
Prof. Dr. Claudio Santi
Guest Editors

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Keywords

  • selenoenzyme models
  • selenosugars
  • biomimetics
  • reactive oxygen species
  • nanoparticles
  • chalcogen bond
  • catalytic reactions
  • organoselenium compounds

Published Papers (7 papers)

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Research

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8 pages, 1080 KiB  
Communication
Demonstration of the Formation of a Selenocysteine Selenenic Acid through Hydrolysis of a Selenocysteine Selenenyl Iodide Utilizing a Protective Molecular Cradle
by Kei Goto, Ryutaro Kimura, Ryosuke Masuda, Takafumi Karasaki and Shohei Sase
Molecules 2023, 28(24), 7972; https://doi.org/10.3390/molecules28247972 - 06 Dec 2023
Viewed by 706
Abstract
Selenocysteine selenenic acids (Sec–SeOHs) and selenocysteine selenenyl iodides (Sec–SeIs) have long been recognized as crucial intermediates in the catalytic cycle of glutathione peroxidase (GPx) and iodothyronine deiodinase (Dio), respectively. However, the observation of these reactive species remained elusive until our recent study, where [...] Read more.
Selenocysteine selenenic acids (Sec–SeOHs) and selenocysteine selenenyl iodides (Sec–SeIs) have long been recognized as crucial intermediates in the catalytic cycle of glutathione peroxidase (GPx) and iodothyronine deiodinase (Dio), respectively. However, the observation of these reactive species remained elusive until our recent study, where we successfully stabilized Sec–SeOHs and Sec–SeIs using a protective molecular cradle. Here, we report the first demonstration of the chemical transformation from a Sec–SeI to a Sec–SeOH through alkaline hydrolysis. A stable Sec–SeI derived from a selenocysteine methyl ester was synthesized using the protective cradle, and its structure was determined by crystallographic analysis. The alkaline hydrolysis of the Sec–SeI at −50 °C yielded the corresponding Sec–SeOH in an 89% NMR yield, the formation of which was further confirmed by its reaction with dimedone. The facile and nearly quantitative conversion of the Sec–SeI to the Sec–SeOH not only validates the potential involvement of this process in the catalytic mechanism of Dio, but also highlights its utility as a method for producing a Sec–SeOH. Full article
(This article belongs to the Special Issue Advances in Selenium Catalysts and Antioxidants)
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24 pages, 6380 KiB  
Article
Chemistry Related to the Catalytic Cycle of the Antioxidant Ebselen
by Kai N. Sands, Austin L. Burman, Esther Ansah-Asamoah and Thomas G. Back
Molecules 2023, 28(9), 3732; https://doi.org/10.3390/molecules28093732 - 26 Apr 2023
Cited by 2 | Viewed by 1549
Abstract
The antioxidant drug ebselen has been widely studied in both laboratories and in clinical trials. The catalytic mechanism by which it destroys hydrogen peroxide via reduction with glutathione or other thiols is complex and has been the subject of considerable debate. During reinvestigations [...] Read more.
The antioxidant drug ebselen has been widely studied in both laboratories and in clinical trials. The catalytic mechanism by which it destroys hydrogen peroxide via reduction with glutathione or other thiols is complex and has been the subject of considerable debate. During reinvestigations of several key steps, we found that the seleninamide that comprises the first oxidation product of ebselen underwent facile reversible methanolysis to an unstable seleninate ester and two dimeric products. In its reaction with benzyl alcohol, the seleninamide produced a benzyl ester that reacted readily by selenoxide elimination, with formation of benzaldehyde. Oxidation of ebselen seleninic acid did not afford a selenonium seleninate salt as previously observed with benzene seleninic acid, but instead generated a mixture of the seleninic and selenonic acids. Thiolysis of ebselen with benzyl thiol was faster than oxidation by ca. an order of magnitude and produced a stable selenenyl sulfide. When glutathione was employed, the product rapidly disproportionated to glutathione disulfide and ebselen diselenide. Oxidation of the S-benzyl selenenyl sulfide, or thiolysis of the seleninamide with benzyl thiol, afforded a transient thiolseleninate that also readily underwent selenoxide elimination. The S-benzyl derivative disproportionated readily when catalyzed by the simultaneous presence of both the thiol and triethylamine. The phenylthio analogue disproportionated when exposed to ambient or UV (360 nm) light by a proposed radical mechanism. These observations provide additional insight into several reactions and intermediates related to ebselen. Full article
(This article belongs to the Special Issue Advances in Selenium Catalysts and Antioxidants)
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10 pages, 2171 KiB  
Article
Controlling the Redox Catalytic Activity of a Cyclic Selenide Fused to 18-Crown-6 by the Conformational Transition Induced by Coordination to an Alkali Metal Ion
by Michio Iwaoka, Hajime Oba and Takeru Ito
Molecules 2023, 28(8), 3607; https://doi.org/10.3390/molecules28083607 - 20 Apr 2023
Viewed by 964
Abstract
trans-3,4-Dihydroxyselenolane (DHS), a water-soluble cyclic selenide, exhibits selenoenzyme-like unique redox activities through reversible oxidation to the corresponding selenoxide. Previously, we demonstrated that DHS can be applied as an antioxidant against lipid peroxidation and a radioprotector by means of adequate modifications of the [...] Read more.
trans-3,4-Dihydroxyselenolane (DHS), a water-soluble cyclic selenide, exhibits selenoenzyme-like unique redox activities through reversible oxidation to the corresponding selenoxide. Previously, we demonstrated that DHS can be applied as an antioxidant against lipid peroxidation and a radioprotector by means of adequate modifications of the two hydroxy (OH) groups. Herein, we synthesized new DHS derivatives with a crown-ether ring fused to the OH groups (DHS-crown-n (n = 4 to 7), 14) and investigated their behaviors of complex formation with various alkali metal salts. According to the X-ray structure analysis, it was found that the two oxygen atoms of DHS change the directions from diaxial to diequatorial by complexation. The similar conformational transition was also observed in solution NMR experiments. The 1H NMR titration in CD3OD further confirmed that DHS-crown-6 (3) forms stable 1:1 complexes with KI, RbCl and CsCl, while it forms a 2:1 complex with KBPh4. The results suggested that the 1:1 complex (3·MX) exchanges the metal ion with metal-free 3 through the formation of the 2:1 complex. The redox catalytic activity of 3 was evaluated using a selenoenzyme model reaction between H2O2 and dithiothreitol. The activity was significantly reduced in the presence of KCl due to the complex formation. Thus, the redox catalytic activity of DHS could be controlled by the conformational transition induced by coordination to an alkali metal ion. Full article
(This article belongs to the Special Issue Advances in Selenium Catalysts and Antioxidants)
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13 pages, 5785 KiB  
Article
Selenonium Salt as a Catalyst for Nucleophilic Substitution Reactions in Water: Synthesis of Thiocyanites and Selenocyanates
by Alix Y. Bastidas Ángel, Philipe Raphael O. Campos and Eduardo E. Alberto
Molecules 2023, 28(7), 3056; https://doi.org/10.3390/molecules28073056 - 29 Mar 2023
Viewed by 1559
Abstract
Organothiocyanates and selenocyanates are valuable compounds, both in terms of functional group interconversion and due to their biological activities. In this contribution, we report the synthesis of a series of these important substances in a mixture of water and dimethyl carbonate (20/1 proportion) [...] Read more.
Organothiocyanates and selenocyanates are valuable compounds, both in terms of functional group interconversion and due to their biological activities. In this contribution, we report the synthesis of a series of these important substances in a mixture of water and dimethyl carbonate (20/1 proportion) using potassium thio- or selenocyanates salts and organic bromides. The key to the effectiveness of the reaction is a chalcogen bond interaction between a selenonium salt catalyst and the organic substrate. Full article
(This article belongs to the Special Issue Advances in Selenium Catalysts and Antioxidants)
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Review

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45 pages, 11208 KiB  
Review
Recent Advances in the Synthesis and Antioxidant Activity of Low Molecular Mass Organoselenium Molecules
by João M. Anghinoni, Paloma T. Birmann, Marcia J. da Rocha, Caroline S. Gomes, Michael J. Davies, César A. Brüning, Lucielli Savegnago and Eder J. Lenardão
Molecules 2023, 28(21), 7349; https://doi.org/10.3390/molecules28217349 - 30 Oct 2023
Cited by 4 | Viewed by 1323
Abstract
Selenium is an essential trace element in living organisms, and is present in selenoenzymes with antioxidant activity, like glutathione peroxidase (GPx) and thioredoxin reductase (TrxR). The search for small selenium-containing molecules that mimic selenoenzymes is a strong field of research in organic and [...] Read more.
Selenium is an essential trace element in living organisms, and is present in selenoenzymes with antioxidant activity, like glutathione peroxidase (GPx) and thioredoxin reductase (TrxR). The search for small selenium-containing molecules that mimic selenoenzymes is a strong field of research in organic and medicinal chemistry. In this review, we review the synthesis and bioassays of new and known organoselenium compounds with antioxidant activity, covering the last five years. A detailed description of the synthetic procedures and the performed in vitro and in vivo bioassays is presented, highlighting the most active compounds in each series. Full article
(This article belongs to the Special Issue Advances in Selenium Catalysts and Antioxidants)
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50 pages, 14575 KiB  
Review
Recent Advances in the Use of Diorganyl Diselenides as Versatile Catalysts
by Gabriel Pereira da Costa, Gustavo Bierhals Blödorn, Angelita Manke Barcellos and Diego Alves
Molecules 2023, 28(18), 6614; https://doi.org/10.3390/molecules28186614 - 14 Sep 2023
Cited by 2 | Viewed by 772
Abstract
The importance of organoselenium compounds has been increasing in synthetic chemistry. These reagents are well-known as electrophiles and nucleophiles in many organic transformations, and in recent years, their functionality as catalysts has also been largely explored. The interest in organoselenium-based catalysts is due [...] Read more.
The importance of organoselenium compounds has been increasing in synthetic chemistry. These reagents are well-known as electrophiles and nucleophiles in many organic transformations, and in recent years, their functionality as catalysts has also been largely explored. The interest in organoselenium-based catalysts is due to their high efficacy, mild reaction conditions, strong functional compatibility, and great selectivity. Allied to organoselenium catalysts, the use of inorganic and organic oxidants that act by regenerating the catalytic species for the reaction pathway is common. Here, we provide a comprehensive review of the last five years of organic transformations promoted by diorganyl diselenide as a selenium-based catalyst. This report is divided into four sections: (1) cyclisation reactions, (2) addition reactions and oxidative functionalisation, (3) oxidation and reduction reactions, and (4) reactions involving phosphorus-containing starting materials. Full article
(This article belongs to the Special Issue Advances in Selenium Catalysts and Antioxidants)
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26 pages, 3699 KiB  
Review
Nontoxic Levels of Se-Containing Compounds Increase Survival by Blocking Oxidative and Inflammatory Stresses via Signal Pathways Whereas High Levels of Se Induce Apoptosis
by Jong-Keol An, An-Sik Chung and David G. Churchill
Molecules 2023, 28(13), 5234; https://doi.org/10.3390/molecules28135234 - 05 Jul 2023
Cited by 3 | Viewed by 1333
Abstract
Selenium is a main group element and an essential trace element in human health. It was discovered in selenocysteine (SeC) by Stadtman in 1974. SeC is an encoded natural amino acid hailed as the 21st naturally occurring amino acid (U) present in several [...] Read more.
Selenium is a main group element and an essential trace element in human health. It was discovered in selenocysteine (SeC) by Stadtman in 1974. SeC is an encoded natural amino acid hailed as the 21st naturally occurring amino acid (U) present in several enzymes and which exquisitely participates in redox biology. As it turns out, selenium bears a U-shaped toxicity curve wherein too little of the nutrient present in biology leads to disorders; concentrations that are too great, on the other hand, pose toxicity to biological systems. In light of many excellent previous reviews and the corpus of literature, we wanted to offer this current review, in which we present aspects of the clinical and biological literature and justify why we should further investigate Se-containing species in biological and medicinal contexts, especially small molecule-containing species in biomedical research and clinical medicine. Of central interest is how selenium participates in biological signaling pathways. Several clinical medical cases are recounted; these reports are mainly pertinent to human cancer and changes in pathology and cases in which the patients are often terminal. Selenium was an option chosen in light of earlier chemotherapeutic treatment courses which lost their effectiveness. We describe apoptosis, and also ferroptosis, and senescence clearly in the context of selenium. Other contemporary issues in research also compelled us to form this review: issues with CoV-2 SARS infection which abound in the literature, and we described findings with human patients in this context. Laboratory scientific studies and clinical studies dealing with two main divisions of selenium, organic (e.g., methyl selenol) or inorganic selenium (e.g., sodium selenite), are discussed. The future seems bright with the research and clinical possibilities of selenium as a trace element, whose recent experimental clinical treatments have so far involved dosing simply and inexpensively over a set of days, amounts, and time intervals. Full article
(This article belongs to the Special Issue Advances in Selenium Catalysts and Antioxidants)
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