Cyprinidae fish can synthesize (3S,3´S)-astaxanthin from zeaxanthin by oxidative metabolic conversion.
On the other hand, Perciformes and Salmonidae fish cannot synthesize astaxanthin from other carotenoids
(Matsunoet al., 2001). Therefore, astaxanthin present in these fish originates from dietary crustacean
zooplankton. Astaxanthin in these fish comprises three optical isomers. Perciformes and Salmonidaefish can
convert astaxanthin to zeaxanthin (Matsuno et al., 1985). Therefore, zeaxanthin in these fish also exist as three
optical isomers (Maoka et al., 1986).
Tunaxanthin is widely distributed in fish belonging to Perciformes. The bright yellow color in the fins and
skin of marine fish is due to the presence of tunaxanthin. Feeding experiments involving red sea bream and