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Quantification of thiopurine/UVA-induced singlet oxygen production

Paper ID Volume ID Publish Year Pages File Format Full-Text
27321 44016 2011 9 PDF Available
Title
Quantification of thiopurine/UVA-induced singlet oxygen production
Abstract

Thiopurines were examined for their ability to produce singlet oxygen (1O2) with UVA light. The target compounds were three thiopurine prodrugs, azathioprine (Aza), 6-mercaptopurine (6-MP) and 6-thioguanine (6-TG), and their S-methylated derivatives of 6-methylmercaptopurine (me6-MP) and 6-methylthioguanine (me6-TG). Our results showed that these thiopurines were efficient 1O2 sensitizers under UVA irradiation but rapidly lost their photoactivities for 1O2 production over time by a self-sensitized photooxidation of sulfur atoms in the presence of oxygen and UVA light. The initial quantum yields of 1O2 production were determined to be in the range of 0.3–0.6 in aqueous solutions. Substitution of a hydrogen atom with a nitroimidazole or methyl group at S decreased the efficacy of photosensitized 1O2 production as found for Aza, me6-MP and me6-TG. 1O2-induced formation of 8-oxo-7,8-dihydro-2′-dexyguanosine (8-oxodGuo) was assessed by incubation of 6-methylthiopurine/UVA-treated calf thymus DNA with human repair enzyme 8-oxodGuo DNA glycosylase (hOGG1), followed by apurinic (AP) site determination. Because more 8-oxodGuo was formed in Tris D2O than in Tris H2O, 1O2 is implicated as a key species in the reaction. These findings provided quantitative information on the photosensitization efficacy of thiopurines and to some extent revealed the correlations between photoactivity and phototoxicity.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Photosensitized singlet oxygen production was directly observed upon UVA irradiation of thiopurines. ► Thiopurines possess high quantum yields of singlet oxygen production. ► Substitution of a hydrogen atom with methyl group at sulfur position decreases the efficacy of singlet oxygen production. ► Oxidative DNA damage by thiopurines induces guanine base oxidation. ► Phototoxicity of thiopurines via type II energy transfer mechanism was quantitatively confirmed.

Keywords
Singlet oxygen; Thiopurine; UVA; Guanine
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Quantification of thiopurine/UVA-induced singlet oxygen production
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 224, Issue 1, 15 November 2011, Pages 16–24
Authors
, , , , ,
Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us