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A Simple and Efficient Strategy To Enhance the Antioxidant Activities of Amino-Substituted Glutathione Peroxidase Mimics

Bhabak, Krishna P and Mugesh, Govindasamy (2008) A Simple and Efficient Strategy To Enhance the Antioxidant Activities of Amino-Substituted Glutathione Peroxidase Mimics. In: Chemistry- A European Journal, 14 (28). 8640-8651.

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Abstract

The glutathione peroxidase (GPx) activities of some diaryl diselenides incorporating tertiary amino groups were studied with $H_{2}O_{2}$, Cum- OOH, and tBuOOH as substrates and with PhSH as thiol co-substrate. Simple replacement of a hydrogen atom with a methoxy group dramatically enhances the GPx activity. The introduction of methoxy substituents ortho to selenium in N,N-dialkylbenzylamine-based compounds makes the basicity of the amino groups perfect for the catalysis. The presence of 6-OMe groups prevents possible Se···N interactions in the selenols, increasing their zwitterionic characters. The methoxy substituents also protect the selenium in the selenenic acid intermediates from overoxidation to seleninic acids or irreversible inactivation to selenonic acid derivatives. The additional substituents also play a crucial role in the selenenyl sulfide intermediates, by preventing thiol exchange reactions—which would normally lead to an inactivation pathway —at the selenium centers. The strengths of Se···N interactions in the selenenyl sulfide intermediates are dramatically reduced upon introduction of the methoxy substituents, which not only reduce the thiol exchange reactions at selenium but also enhance the nucleophilic attack of the incoming thiols at sulfur. The facile attack of thiols at sulfur in the selenenyl sulfides also prevents the reactions between the selenenyl sulfides and $H_{2}O_{2}$, that can regenerate the selenenic acids (reverse- GPx cycle). These studies reveal that the simple 6-OMe groups play multiple roles in each of the catalytically active intermediates by introducing steric and electronic effects that are required for efficient catalysis.

Item Type: Journal Article
Additional Information: copyright of this article belongs to Wiley-VCH Verlag GmbH&Co.
Keywords: antioxidant activity;GPx mimics;noncovalent interactions;selenium;selenoenzymes
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 19 Dec 2008 15:28
Last Modified: 19 Sep 2010 04:52
URI: http://eprints.iisc.ernet.in/id/eprint/16527

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