Generation of superoxide and singlet oxygen from α-tocopherolquinone and analogues.

Crisostomo, AG; Moreno, RB; Navaratnam, S; Wilkinson, JA; Bisby, RH

Abstract

Three potential routes to generation of reactive oxygen species from a tocopherolquinone have been identified. The quinone of the water-soluble vitamin E analogue Trolox C (Trol-Q) is reduced by hydrated electron and isopropanol a hydroxyalkyl radical, and the resulting semiquinone reacts with molecular oxygen to form superoxide with a second order rate constant of 1.3 x 108 dm3 mol-1 s-1, illustrating the potential for redox cycling. Illumination (UV-A, 355 nm) of the quinone of 2,2,5,7,8-pentamethyl-6-hydroxychromanol (PMHC-Q) leads to a reactive short-lived (ca 10-6 s) triplet state, able to oxidise tryptophan with a second order rate constant greater than 109 dm3 mol-1 s-1. The triplet states of these quinones sensitize singlet oxygen formation with quantum yields of about 0.8. Such potentially damaging reactions of a tocopherolquinone may in part account for the recent findings that high levels of dietary vitamin E supplementation lack any beneficial effect and may lead to slightly enhanced levels of overall mortality.

Citation

Crisostomo, A., Moreno, R., Navaratnam, S., Wilkinson, J., & Bisby, R. (2007). Generation of superoxide and singlet oxygen from α-tocopherolquinone and analogues. Free Radical Research, 41(6), 730-737. https://doi.org/10.1080/10715760701324075

• Journal Article Type: Article
• Publication Date: Jun 1, 2007
• Deposit Date: Jul 26, 2007
• Publicly Available Date: Jul 26, 2007
• Journal: Free Radical Research
• Print ISSN: 1071-5762
• Publisher: Taylor and Francis
• Peer Reviewed: Not Peer Reviewed
• Volume: 41
• Issue: 6
• Pages: 730-737
• DOI: https://doi.org/10.1080/10715760701324075
• Related Public URLs: http://www.informaworld.com/smpp/content?content=10.1080/10715760701324075