New Acetylenic Carotenoid 6'-Epimonadoxanthin from the Rosary Goby Gymnogobius castaneus.

Carotenoids of the rosary goby Gymnogobius castaneus (juzukakehaze in Japanese) were investigated. A new acetylenic carotenoid, (3R,3'R,6'S)-7,8-didehydro-β,ε-carotene-3,3'-diol (1), named 6'-epimonadoxanthin, was isolated along with 18 known carotenoids. The structure of 6'-epimonadoxanthin was determined by UV-VIS, ESI-TOF MS, H-NMR, and CD spectral data. The metabolic pathway from diatoxanthin to 6'-epimonadoxanthin is also discussed.