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Tertiary amine-based glutathione peroxidase mimics: some insights into the role of steric and electronic effects on antioxidant activity

Bhowmick, Debasish and Mugesh, Govindasamy (2012) Tertiary amine-based glutathione peroxidase mimics: some insights into the role of steric and electronic effects on antioxidant activity. In: TETRAHEDRON, 68 (51). pp. 10550-10560.

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Official URL: http://dx.doi.org/10.1016/j.tet.2012.09.020

Abstract

In this work, several tertiary amine-based diaryl diselenides were synthesized and evaluated for their glutathione peroxidase (GPx)-like antioxidant activities using hydrogen peroxide, tert-butyl hydroperoxide and cumene hydroperoxide as substrates and thiophenol (PhSH) and glutathione (GSH) as co-substrates. A comparison of the GPx-like activity of 4-methoxy-substituted N,N-dialkylbenzylamine-based diselenides with that of the corresponding 6-methoxy-substituted compounds indicates that the activity highly depends on the position of the methoxy substituent. Although the methoxy group at 4- and 6-position alters the electronic properties of selenium, the substitution at the 6-position provides the required steric protection for some of the key intermediates in the catalytic cycle. A detailed experimental and theoretical investigation reveals that the 6-methoxy substituent prevents the undesired thiol exchange reactions at the selenium centers in the selenenyl sulfide intermediates. The 6-methoxy substituent also prevents the formation of seleninic and selenonic acids. When PhSH is used as the thiol co-substrate, the 4-methoxy-substituted diselenides exhibit GPx-like activity similar to that of the parent compounds as the 4-methoxy substituent does not block the selenium center in the selenenyl sulfide intermediates from thiol exchange reactions. In contrast, the 4-methoxy substituent significantly enhances the GPx-like activity of the diselenides when glutathione (GSH) is used as the co-substrate. (C) 2012 Elsevier Ltd. All rights reserved.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to PERGAMON-ELSEVIER SCIENCE LTD, OXFORD ,ENGLAND
Keywords: Antioxidant activity;GPx mimics;Selenoenzymes;Selenium;Thiol exchange
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Depositing User: Francis Jayakanth
Date Deposited: 31 Jan 2013 12:47
Last Modified: 31 Jan 2013 12:47
URI: http://eprints.iisc.ac.in/id/eprint/45693

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