Antioxidant Activity of the Anti-Inflammatory Compound Ebselen: A Reversible Cyclization Pathway via Selenenic and Seleninic Acid Intermediates

Sarma, Bani Kanta and Mugeshii, Govindasamy (2008) Antioxidant Activity of the Anti-Inflammatory Compound Ebselen: A Reversible Cyclization Pathway via Selenenic and Seleninic Acid Intermediates. In: Chemistry-A European Journal, 14 (34). pp. 10603-10614.

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Abstract

A revised mechanism that accounts for the glutathione peroxidase (GPx)-like catalytic activity of the organoselenium compound ebselen is described. It is shown that the reaction of ebselen with H2O2 yields seleninic acid its the only oxidized product. The X-ray crystal structure of the seleninic acid shows that the selenium atom is involved in a noncovalent interaction with the carbonyl oxygen atom. In the presence of excess thiol, the Se-N bond in ebselen is readily cleaved by the thiol to produce the corresponding selenenyl sulfide. The selenenyl sulfide thus produced undergoes a disproportionation in the presence of H2O2 to produce the diselenide, which upon reaction with H2O2, produces it mixture of selenenic and seleninic acids. The addition of thiol to the Mixture containing selenenic and seleninic acids leads to the formation of the selenenyl sulfide. When the concentration of the thiol is relatively low in the reaction mixture, the selenenic acid undergoes a rapid cyclization to produce ebselen. The seleninic acid, on the other hand. reacts with the diselenide to produce ebselen as the final product. DFT calculations show that the cyclization of selenenic acids to the corresponding selenenyl amides is more favored than that of sulfenic acids to the corresponding sulfenyl amides. This indicates that the regeneration of ebselen under it variety of conditions protects the selenium moiety from irreversible inactivation, which may be responsible for the biological activities of ebselen.

Item Type:	Journal Article
Publication:	Chemistry-A European Journal
Publisher:	WILEY Inter Science.
Additional Information:	Copyright of this article belongs to WILEY Inter Science.
Keywords:	antioxidant activity;ebselen;gluthatione peroxidase mimics;selenium;selenoenzymes
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	06 Mar 2009 10:51
Last Modified:	19 Sep 2010 04:58
URI:	http://eprints.iisc.ac.in/id/eprint/17851

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