The dried powder of Paracoccus carotinifaciens (PANAFERD-AX®) contains (3S,3'S)-astaxanthin as a major carotenoid. Administration of PANAFERD-AX® for pigmentation of the prawn Penaeus japonicus was examined. Total carotenoid contents in the carapace, muscle, and head of the prawn were dose-dependently increased depending on the amount of PANAFERD-AX® administered. Furthermore, not only the amounts of astaxanthins (astaxanthin diester, astaxanthin monoester, and free astaxanthin) but also the

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... unts of yellow xanthophylls, isoastaxanthin (1), 5,6-dihydropenaeusxanthin (2), penaeusxanthin (3), tetrahydroxypirardixanthin (4), and curstaxanthin (5), were dose-dependently increased with the administration of PANAFERD-AX®. 5,6-Dihydropenaeusxanthin (2) and penaeusxanthin (3) are new carotenoids isolated from the prawn P. japonicus. These structures were determined to be (3R,4S,5R,6R,6'S)-5,6-dihydro-3,4,4'- trihydroxy-β,ε-caroten-3'-one (2) and (3R,4S,6'S)-3,4,4'-trihydroxy-β,ε-caroten-3'-one (3) by UV/vis, ESI TOF MS, 1H NMR, and CD spectral data. The metabolism of astaxanthin to these yellow xanthophylls in the prawn was discussed.