Carotenoid radical interaction oxygen

Spin trapping methods were also used to show that when carotenoid-P-cyclodextrin 1 1 inclusion complex is formed (Polyakov et al. 2004), cyclodextrin does not prevent the reaction of carotenoids with Fe3+ ions but does reduce their scavenging rate toward OOH radicals. This implies that different sites of the carotenoid interact with free radicals and the Fe3+ ions. Presumably, the OOH radical attacks only the cyclohexene ring of the carotenoid. This indicates that the torus-shaped cyclodextrins, Scheme 9.6, protects the incorporated carotenoids from reactive oxygen species. Since cyclodextrins are widely used as carriers and stabilizers of dietary carotenoids, this demonstrates a mechanism for their safe delivery to the cell membrane before reaction with oxygen species occurs. 

Carotenoid Radicals and the Interaction of Carotenoids with Active Oxygen Species... 

The interaction of carotenoids and carotenoid radicals with other anti-oxidants is of importance with respect to anti-oxidative and possibly pro-oxidative reactions of carotenoids. All the radical cations of the carotenoids studied reacted with vitamin C so as to repair the carotenoid (e.g. in methanol, CAR t AscH CAR + AscH -I- H ). hi polar environments the vitamin E radical cation is deprotonated (TOH —> TO -i- H ) and TO does not react with carotenoids, whereas in non-polar environments, TOH is converted into TOH by hydrocarbon carotenoids, hi aU solvents studied, singlet oxygen is efficiently quenched by carotenoids that have appropriate low-lying triplet energy levels O -i- CAR -> Oj -i- CAR". However, such reactions are stiU to be observed in vivo. 

Edge R, Land EJ, McGarvey D, Mulroy L and Tmscott TG (1998) Relative one-electron reduction potentials of carotenoid radical cations and the interactions of carotenoids with the vitamin E radical cation. J AmerChem Soc 120 4087-4090 Everett SA, Dennis MF, Patel KB, Maddix S, Kundu SC and Willson RL (1996) Scavengingofnitrogendioxide, thiyl, and sulphonyl free radicals by the nutritional anti-oxidant fi-carotene. J Biol Chem 271 3988-3994 Foote CS and Denny RW (1968) Chemistry of singlet oxygen. 

Carotenoid radical cations are formulated as intermediates in various reactions between carotenoids and reactive oxygen species [50,52], Carotenoids may interact with free radicals in three different ways [50] ... 

Krinsky, N. I. and S. M. Deneke (1982). Interaction of oxygen and oxy-radicals with carotenoids. J. Natl. Cancer Inst. 69(1) 205-210. 

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