Nitration reactions of astaxanthin and β-carotene by peroxynitrite

The in vitro reactivities of astaxanthin and beta-carotene toward peroxynitrite were investigated and the reaction products after scavenging with peroxynitrite were analyzed. A series of carotenoids substituted with nitro group, 14'-s-cis-15'-nitroastaxanthin, 10'-s-cis-11'-cis-11'-nitroastaxanthin, 14'-s-cis-15'-nitro-beta-carotene and 10'-s-cis-11'-cis-11'-nitro-beta-carotene, were isolated from the reaction products of carotenoids with peroxynitrite. Carotenoids with nitro derivatives were reported for the first time. These results indicated that astaxanthin and P-carotene could catch peroxynitrite or nitrogen dioxide radical ((NO2)-N-*) in their molecule to form nitrocarotenoids. (c) 2006 Elsevier Ltd. All rights reserved.