Astaxanthin and its metabolites idoxanthin and crustaxanthin in flesh, skin, and gonads of sexually immature and maturing Arctic charr (Salvelinus alpinus (L.))

Carotenoid compositions of the flesh, skin, and ovaries were determined in sexually maturing and immature Arctic charr (Salvelinus alpinus) fed diets supplemented with astaxanthin (optical isomer ratio (3S,3'S):(3R,3'S; meso) :(3R,3'R); 1:2:1). Astaxanthin comprised 64-79% of the flesh carotenoids, a nd the 3',4'-cis and 3',4'-trans glycolic isomers of idoxanthin, present in a 1:1 ratio, represented 20-35%. The flesh of the sexually maturing charr contained relatively more idoxanthin than that of sexually immature fish (2 0 vs 35% of total carotenoids), possibly being indicative of a higher metab olic turnover of astaxanthin in the latter. The relative proportions of fle sh carotenoids were unaffected by sex. The relative carotenoid composition of ovaries was similar in sexually maturing and immature females. The 3',4' -cis and 3',4'-trans glycolic isomers of idoxanthin (ratio 0.7:1) were the major carotenoids (56% of total), followed by crustaxanthin (20%), and asta xanthin comprised less than 5% of ovarian carotenoids. Three glycolic isome rs of crustaxanthin were detected (3,4,3',4'-di-cis-:3,4-cis-3',4'-trans-:3 ,4,3'4'-di-trans-glycolic isomer ratio 2.6:3.1:1) in the ovaries. Sex and m aturity status had no apparent effect on the relative composition of skin c arotenoids. The Skin carotenoids consisted mainly of diesters (82-87% of to tal carotenoids) and monoesters (7-13% of total carotenoids). Saponificatio n revealed that astaxanthin comprised 85%, and idoxanthin 10% of total caro tenoids, and minor amounts of tunaxanthin-, lutein-, and zeaxanthin-like me tabolites were also present. Maturity status seems to be more important tha n sex in determining the relative carotenoid composition of the tissues of Arctic charr, with astaxanthin and its metabolites being selectively accumu lated in different tissues. (C) 2000 Elsevier Science Inc. All rights reser ved.