INTERACTIONS BETWEEN CAROTENOIDS AND THE CCL3O2-CENTER-DOT RADICAL

The reactions of CCl3O2. (a model of alkyl peroxyl radicals which can be selectively generated in nanoseconds) with a range of carotenoids ( beta-carotene, septapreno-beta-carotene, canthaxanthin, astaxanthin, z eaxanthin, and lutein) in the heterogeneous micellar environment, aque ous 2% Triton X-100, have been studied by pulse radiolysis. For all ca rotenoids investigated two reaction products, absorbing in the near-in frared region, are observed and assigned to the carotenoid radical cat ion and an addition radical. With the exception of astaxanthin, the ca rotenoid radical cation formation is biexponential and the slower comp onent matches the first-order decay of the addition radical. In the ca se of astaxanthin, no radical cation is formed directly by reaction wi th CCl3O2., it is formed exclusively from the decay of the addition ra dical. The results are discussed in terms of the antioxidant propertie s of carotenoid pigments.