The in vitro reactivities of astaxanthin toward peroxynitrite were investigated and the reaction products after scavenging with peroxynitrite were analyzed in order to determine the complete mechanism of this reaction. A series of carotenoids, 13-apo-astaxanthinone (1), 12'-apo-15'-nitroastaxanthinal (2), 12'-apo-astaxanthinal (3), 10'-apo-astaxanthinal (4), 9-cis-14'-s-cis-15'-nitroastaxanthin (5), 14'-s-cis-15'-nitroastaxanthin (6), 13-cis-14'-s-cis-15'-nitroastaxanthin (7), 10'-s-cis-11'-cis-11'-nitroastaxanthin (8), 13,15,13'-tri-cis-15'-nitroastaxanthin (9), 9-cis-astaxanthin (10), and 13-cis-astaxanthin (11), were isolated from the reaction products of carotenoids with peroxynitrite. Our previous studies achieved for the first time the isolation of nitro derivatives from the reaction of astaxanthin with peroxynitrite. Here we identify the major remaining reaction products of this reaction and investigate the stabilities of the nitro astaxanthins.