The structure of two new marine carotenoids, isolated from the tunicate, Amaroucium pliciferum, and designated as amarouciaxanthin A and B, were determined on the basis of chemical and spectral data. Amarouciaxanthin A was determined as (6S, 3'S, 5'R,6'R)- 6,3',5'-trihydroxy-4,5,6',7'-tetradehydro-7,8,5',6'-tetrahydro-beta, beta-carotene-3,8-dione, and Amarouciaxanthin B was determined as (6S,3'R)-6,3'-dihydroxy-4,5,7',8'-tetradehydro-7,8-dihydro-beta,beta- carotene-3,8-dione. These two compounds are also presumed to be new metabolic products of a typical marine carotenoid, fucoxanthin.

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A new marine carotenoid, mytiloxanthinone (3,8′-dihydroxy-7,8-didehydro-β,κ-carotene-3′,6′-dione) has been isolated from sea squirt, Halocynthia roretzi.

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