Scavenging of benzylperoxyl radicals by carotenoids

Carotenoids scavenge simple lipid-like alkylperoxyl radicals. However, the rate constant is too low to be determined directly and the mechanism is likewise not known with certainty [Mortensen, A. and Skibsted, L.H. (1998) FEBS Lett. 426, 392-396]. It is demonstrated that carotenoids react with peroxyl radicals only slightly more reactive than lipidperoxyl radicals neither by electron transfer nor by hydrogen atom donation, but by adduct formation. Benzylperoxyl radicals are scavenged by the carotenoids beta-carotene and canthaxanthin with a second-order rate constant of at least 1 x 10(6) M(-1) s(-1) by formation of an adduct which decays in a first-order reaction.