Carotenoids in three species of Corbicula Clams, Corbicula japonica, Corbicula sandai, and Corbicula sp. (Chinese Freshwater Corbicula Clam).

Carotenoids were investigated in three species of corbicula clams, Corbicula japonica, Corbicula sandai, and Corbicula sp. (Chinese freshwater corbicula clam). Forty-three carotenoids were isolated. Among them, 7,8-didehydro-beta-cryptoxanthin (12), peridininol 5,8-furanoxide (38), pyrrhoxanthin 5,8-furanoxide (40), and pyrrhoxanthinol 5,8-furanoxide (43) are newly reported as naturally occurring carotenoids. Their structures were characterized on the basis of UV-vis, FAB-MS including MS/MS experiments, and 1H NMR spectroscopic data. The total carotenoid contents in C. japonica, C. sandai, and Chinese freshwater corbicula clam were found to be 5.3, 2.6, and 0.3 mg/100 g in the edible part (wet weight), respectively. Peridinin (34) and its derivatives were found to be major carotenoids in C. japonica, which inhabits brackish water. On the other hand, lutein (13) was found to be the major carotenoid in C. sandai and Chinese corbicula clams, which inhabit freshwater. These patterns well reflected the carotenoids in their dietary algae. 7',8'-Didehydrodeepoxyneoxanthin (19), corbiculaxanthin (21), corbiculaxanthin 3'-acetate (22), and 6-epiheteroxanthin (24) were found in all three species of corbicula clams and have not previously been found in other shellfishes. They were assumed to be peculiar carotenoids in corbicula clams.