COMPARATIVE BIOCHEMICAL-STUDIES OF CAROTENOIDS IN SEA-CUCUMBERS

The results of an investigation of the carotenoids in the seven species of sea cucumber (Stichopus japonicus, Holothuria leucospilota, H, moebi and H, pervicax of the order Aspidochirotida, Cucumaria japonica, C, echinata and Pentacta australis of the order Dendrochirotida), from the comparative biochemical point of view, are reported, beta-Carotene, beta-echinenone, canthaxanthin, phoenicoxanthin and astaxanthin were common in all the sea cucumbers examined, A series of novel marine carotenoids (cucumariaxanthin A, B and C) was obtained from the sea cucumbers of the order Dendrochirotida, while they could not be found from those of the order Aspidochirotida, Significant differences in the carotenoid patterns of the two orders were also observed, The structures of cucumariaxanthin A, B and C have been determined, by chemical and spectroscopic investigations, to be (9Z,9'Z)-5,6,5',6'-tetrahydro-beta,beta-carotene-4,4'-dione, (9Z,9'Z)-4'-hydroxy-5,6,5',6'-tetrahydro-beta,beta-caroten-4-one, and (9Z,9'Z)-5,6,5',6'-tetrahydro-beta,beta-carotene-4,4'-diol respectively. From the experimental results of carotenoids in the sea cucumbers examined, an oxidative metabolic pathway for beta-carotene to astaxanthin, and a new reductive and isomeric metabolic pathway for canthaxanthin to cucumariaxanthin C (via cucumariaxanthin A and B) are proposed.