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Chain-Breaking Phenolic 2,3-Dihydrobenzo[b]selenophene Antioxidants: Proximity Effects and Regeneration Studies
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Organisk kemi. Centre of Advanced Studies in Chemistry, Panjab University, India.ORCID-id: 0000-0002-5584-2067
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Organisk kemi. (Lars Engman)ORCID-id: 0000-0003-0689-3180
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Organisk kemi. (Lars Engman)ORCID-id: 0000-0002-5568-7415
School of Chemistry, University of Bristol, United Kingdom.
Vise andre og tillknytning
2017 (engelsk)Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, nr 60, s. 15080-15088Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Phenolic 2,3-dihydrobenzo[b]selenophene anti-oxidants carrying the OH-group ortho (9), meta (10, 11) and para (8) to the Se were prepared by seleno-Claisen rearrangement/intramolecular hydroselenation. Meta-isomer (11) was studied by X-ray crystallography. The radical-trapping activity and regenerability of compounds 8-11 were evaluated using a two-phase system where linoleic acid was undergoing peroxidation in the lipid phase while regeneration of the antioxidant by co-antioxidants (N-acetylcysteine, glutathione, dithiothreitol, ascorbic acid, tris(carboxyethyl)phosphine hydrochloride) was ongoing in the aqueous layer. Compound 9 quenched peroxyl radicals

more efficiently than α-tocopherol. It also provided the most long-lasting antioxidant protection. With thiol co-antioxidants it could inhibit peroxidation for more than five-fold longer than the natural product. Regeneration was more efficient when the aqueous phase pH was slightly acidic. Since calculated O-H bond dissociation energies for 8-11 were substantially larger than for α-tocopherol, an antioxidant mechanism involving O-atom transfer from peroxyl to selenium was proposed. The resulting phenolic selenoxide/alkoxyl radical would then exchange a hydrogen atom in a solvent cage before antioxidant regeneration at the aqueous lipid interphase.

sted, utgiver, år, opplag, sider
2017. Vol. 23, nr 60, s. 15080-15088
Emneord [en]
chain-breaking antioxidants, phenols, dihydrobenzoselenophenes, lipid peroxidation, co-antioxidants
HSV kategori
Forskningsprogram
Kemi med inriktning mot organisk kemi
Identifikatorer
URN: urn:nbn:se:uu:diva-329201DOI: 10.1002/chem.201702350ISI: 000413768900018PubMedID: 28857289OAI: oai:DiVA.org:uu-329201DiVA, id: diva2:1139907
Tilgjengelig fra: 2017-09-10 Laget: 2017-09-10 Sist oppdatert: 2018-02-23bibliografisk kontrollert
Inngår i avhandling
1. Regenerable Organochalcogen Antioxidants: An Explorative Study
Åpne denne publikasjonen i ny fane eller vindu >>Regenerable Organochalcogen Antioxidants: An Explorative Study
2017 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Antioxidants are widely used to protect organic materials from damages caused by autoxidation, an oxidation process that occurs under normal aerobic conditions. In this thesis, novel multifunctional organoselenium and organotellurium antioxidants were designed, synthesized, and evaluated in search for compounds with better radical-trapping capacity, regenerability, and hydroperoxide-decomposing ability.

Selenium was incorporated into ebselenols and hydroxy-2,3-dihydrobenzo[b]selenophenes and tellurium into diaryl disulfides and aryltellurophenols. All newly developed antioxidants were evaluated in a chlorobenzene/water two-phase lipid peroxidation system containing suitable co-antioxidants in the aqueous phase. Ebselenol carrying a hydroxyl group (OH) ortho to selenium showed a two-fold longer inhibition time than the reference α-tocopherol in the presence of aqueous-phase ascorbic acid. 2,3-Dihydrobenzo[b]selenophenes carrying a 5- or 7-OH outperformed α-tocopherol both when it comes to radical-trapping capacity and regenerability. Alkyltellurothiophenols, in situ formed from their corresponding disulfides by tris(2-carboxyethyl)phosphine, were also efficient regenerable radical-trapping antioxidants. The consumption of N-acetylcysteine in the water phase was followed and found to be limiting for the duration of the inhibition. The hydroperoxide-decomposing ability of all organoselenium antioxidants was evaluated. Ebselenols were often better glutathione peroxidase mimics than the parent.

In an effort to find out more about antioxidant mechanisms, aryltellurophenols carrying electron donating and electron withdrawing groups in the phenolic or aryltelluro parts were synthesized and OH bond dissociation enthalpies, BDEO-Hs, were calculated. Compounds carrying electron donating groups in the phenolic or aryltelluro part of the molecule showed the best radical-trapping capacity. Deuterium labelling experiments suggested that hydrogen atom transfer could be the rate-limiting step in the antioxidant mechanism.  

sted, utgiver, år, opplag, sider
Uppsala: Acta Universitatis Upsaliensis, 2017. s. 70
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1556
Emneord
autoxidation, antioxidant, selenium, tellurium, regenerable, multifunctional, radical-trapping, hydroperoxide-decomposing, co-antioxidant
HSV kategori
Forskningsprogram
Kemi med inriktning mot organisk kemi
Identifikatorer
urn:nbn:se:uu:diva-329217 (URN)978-91-513-0068-9 (ISBN)
Disputas
2017-10-27, B7:101a, BMC, Husargatan 3, 751 23, Uppsala, 09:30 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2017-10-05 Laget: 2017-09-10 Sist oppdatert: 2017-10-18

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