Astaxanthin

Carotenoid Radical Anions and Their Protonated Derivatives.

El-Agamey A, Edge R, Navaratnam S, Land EJ, Truscott TG.

School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK, Free Radical Research Facility, CCLRC Daresbury Laboratory, Warrington WA4 4AD, UK, and Biosciences Research Institute, University of Salford, Salford M5 4WT, UK.

In this study, we report the protonation reactions for astaxanthin and canthaxanthin radical anions in methanol, alkaline methanol, and aqueous 2% Triton X-100 at different pH values. The pK(a) values for the corresponding alpha-hydroxy radical derivatives of astaxanthin, canthaxanthin, and beta-apo-8'-carotenal were estimated in 2% Triton X-100. Also, the effects of the microenvironment and the structure of the carotenoids on the protonation rate constant are discussed.

PMID: 16956200 [PubMed - as supplied by publisher]