Recent progress on carotenoid metabolism in animals

Abstract

The influence of dietary astaxanthin, canthaxanthin and zeaxanthin on the carotenoid content and composition of the oil droplets in chicken retina was investigated. From a “racemic” astaxanthin mixture, the (3S, 3’S)-isomer was deposited almost selectively in the retina. Both oxidative and reductive metabolic pathways were followed by all three carotenoids. Astaxanthin, the main carotenoid in avian oil droplets, was obviously formed from both dietary zeaxanthin and canthaxanthin. - Egg yolk pigmentation was studied in relation to carotenoid structure. Depositon rates and metabolites of some C30 and C40 carotenoids have been determined. Beta- and Ψ-apo-carotenoids with a terminal methyl group in the y-position were gradually shortened by a type of β-oxidation. - Various yellow metabolites of astaxanthin have been identified in the prawn Penaeus vannamei and their absolute configurations determined. The 4,4’-oxo groups of astaxanthin were reduced stereospecifically, resulting in (4S,4' ‘S)-tetrahydroxypirardixanthin. The presence of the novel, naturally occurring isoastaxanthin [(6S,6'S)-4,4'-dihydroxy-s,e-carotene-3,3'-dione] offered an explanation for a racemization of astaxanthin in vivo, which was proved in Penaeus japonicus after administration of optically active 3H]-labelled astaxanthin. © 1991 IUPAC