Photoprotection and Radiation Protection by Dietary Carotenoids

The dietary carotenoids give photoprotection to photosynthetic systems, the eye, and the skin from reactive oxygen species. Lipids, proteins and DNA are all susceptible to attack by both SO and free radicals. Many carotenoids (CARs) and oxy-carotenoids (xanthophylls) occur naturally in our foodstuffs, and, indeed, several are often added as food colorants, such as ß-carotene, lycopene, lutein, canthaxanthin, ß-apo-8'-carotenal and astaxanthin. The extremely efficient quenching of SO by all C40 CARs and XANs with 11 conjugated double bonds in "simple" organic solvents such as benzene is well established and reviewed in this chapter. One of the earliest studies of electron-donor and electron-acceptor properties of CARs comes from the electrochemical studies. It is now well established that radicals can react with CARs via electron and H-atom transfer and also via addition reactions. The chapter discusses the possible reaction between O2 and crocetin, a water-soluble CAR.