Structures of minor carotenoids from the Japanese common catfish, Silurus asotus.
Three new carotenoids: 7',8',9',10'-tetrahydro-β-cryptoxanthin, 7',8'-dihydrodiatoxanthin, and (3S,6S,6'S)-ε-cryptoxanthin were isolated from the skin, fins, and gonads of the Japanese common catfish, Silurus asotus, as minor carotenoids. Their structures were determined based on chemical and spectroscopic data. Furthermore, 9Z and/or 9'Z geometrical isomers of parasiloxanthin, 7',8'-dihydroparasiloxanthin, and 7',8'-dihydro-β-cryptoxanthin were characterized by (1)H-NMR.