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Alkyltelluro Substitution Improves the Radical-Trapping Capacity of Aromatic Amines
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.ORCID iD: 0000-0002-5568-7415
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
Univ Bristol, Sch Chem, Bristol BS8 1TS, Avon, England.
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2016 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 36, 12891-12903 p.Article in journal (Refereed) Published
Abstract [en]

The synthesis of a variety of aromatic amines carrying an ortho-alkyltelluro group is described. The new antioxidants quenched lipidperoxyl radicals much more efficiently than α-tocopherol and were regenerable by aqueous-phase N-acetylcysteine in a two-phase peroxidation system. The inhibition time for diaryl amine 9 b was four-fold longer than recorded with α-tocopherol. Thiol consumption in the aqueous phase was found to correlate inversely to the inhibition time and the availability of thiol is the limiting factor for the duration of antioxidant protection. The proposed mechanism for quenching of peroxyl radicals involves O-atom transfer from peroxyl to Te followed by H-atom transfer from amine to alkoxyl radical in a solvent cage.

Place, publisher, year, edition, pages
2016. Vol. 22, no 36, 12891-12903 p.
Keyword [en]
antioxidants; amines; chain-breaking activity; organotellurium; regenerable
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-302460DOI: 10.1002/chem.201602377ISI: 000383758200044PubMedID: 27484352OAI: oai:DiVA.org:uu-302460DiVA: diva2:957710
Funder
Swedish Research Council, 621-2011-4006
Available from: 2016-09-04 Created: 2016-09-04 Last updated: 2016-12-20Bibliographically approved
In thesis
1. Exploring Catalytic Tellurium-Based Antioxidants: Synthesis and Evaluation
Open this publication in new window or tab >>Exploring Catalytic Tellurium-Based Antioxidants: Synthesis and Evaluation
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is concerned with the synthesis and evaluation of various tellurium-based chain-breaking antioxidants. The purpose is to find novel regenerable compounds with improved radical-trapping capacity.

In the first part of this work, we explore the possibilities to incorporate tellurium into tocopherols and aromatic amines. Overall, tocopherols carrying alkyltelluro groups are better radical-trapping agents than the corresponding sulfur- and selenium analogues. Among them, 7-octyltelluro δ-tocopherol showed a ca. 17-fold higher reactivity than recorded for α-tocopherol and much better regenerability. Even longer inhibition times were recorded for the corresponding bis(tocopheryl) tellurides. In the aromatic amine series, diphenyl amines carrying alkyltelluro groups were shown to function as efficient radical-quenchers capable of inhibiting peroxidation for 460 min in the presence of N-acetylcysteine. Thiol-consumption experiments suggested that the long inhibition times are due to efficient quenching of in-situ formed alkoxyl radicals in a solvent cage.

In the second part of the thesis, we study how the antioxidant properties are affected by variations in the electron density at tellurium and the number of alkyltelluro substituents in the molecule. Evaluation of a series of aryltelluro phenols carrying electron donating and electron withdrawing groups in the para-position of the aryl moiety suggested that a high electron density at the heteroatom prolonged the inhibition time. Among alkyltelluro phenols, alkyltelluro resorcinols and bis(alkyltelluro) phenols, phenols carrying alkyltelluro groups in both ortho positions were superior when it comes to radical-trapping activity and regenerability.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 72 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1423
Keyword
antioxidant, tellurium, selenium, radical-trapping, chain-breaking, ROS, glutathione peroxidase, tocopherol, aromatic amine, oxidative stress
National Category
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-302475 (URN)978-91-554-9684-5 (ISBN)
Public defence
2016-10-27, B41, BMC, Husargatan 3, Uppsala, 09:30 (English)
Opponent
Supervisors
Available from: 2016-10-03 Created: 2016-09-04 Last updated: 2016-10-03

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