Nitration reactions of astaxanthin and β-carotene by peroxynitrite

Abstract The in vitro reactivities of astaxanthin and β-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-β-carotene and 10′-s- cis -11′- cis -11′-nitro-β-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 β-carotene could catch peroxynitrite or nitrogen dioxide radical ( NO 2 ) in their molecule to form nitrocarotenoids.