Per Foss

Carotenoids in diets for salmonids: I. Pigmentation of rainbow trout with the individual optical isomers of astaxanthin in comparison with canthaxanthin

Abstract Visual and chemical determinations revealed that the individual optical isomers of astaxanthin were more efficacious than canthaxanthin in pigmenting the flesh of rainbow trout ( Salmo gairdneri , Richardson). The visual assessment of the astaxanthin pigmentation by means of a colour scale correlated well with the chemical determination. The same utilization was found for all three astaxanthin isomers, ( 3S, 3′S )-, ( 3R, 3′S )-, ( 3R, 3′R )-astaxanthin and a 1 : 2 : 1 mixture of the three isomers. No epimerization took place at the chiral centres of C-3 and C-3′ in astaxanthin. Astaxanthin and canthaxanthin were not interconverted. No metabolites were detected in the flesh.

Carotenoids in diets for salmonids: IV. Pigmentation of Atlantic salmon with astaxanthin, astaxanthin dipalmitate and canthaxanthin

Abstract Diets supplemented with synthetic astaxanthin, astaxanthin dipalmitate and canthaxanthin at concentrations of 0, 30, 60 and 90 mg/kg, as carotenoid equivalents, were fed to groups of Atlantic salmon (Salmo salar L.) for 56 weeks. The mean initial and final fish weights were 62 and 406 g respectively. There was a tendency for astaxanthin to be more efficiently utilized than canthaxanthin, which in turn was more efficiently utilized than astaxanthin dipalmitate, for flesh pigmentation. These differences were partly explained by differences in the apparent digestibility of the carotenoids. The flesh pigmentation increased with increasing dietary carotenoid concentration. The visual assessments of flesh colour by means of a colour scale correlated well with the chemical determination. The carotenoid content of the skin was higher for the fish fed diets containing carotenoids than for the control groups, but there was no significant difference in the carotenoid concentration in the skin of the fish fed the different carotenoids.

Carotenoids in diets for salmonids: V. Pigmentation of rainbow trout and sea trout with astaxanthin and astaxanthin dipalmitate in comparison with canthaxanthin

Abstract Rainbow trout ( Salmo gairdneri Richardson) and sea trout ( Salmo trutta L.), kept in fresh water, were fed diets containing either 30 mg synthetic astaxanthin (a 1:1:2 mixture of the three optical isomers 3 S , 3′ S , 3 R , 3′ S ) plus 30 mg cantaxanthin/kg (diet i) or 30 mg synthetic astaxanthin dipalmitate (as astaxanthin equivalents) plus 30 mg canthaxanthin/kg (diet ii). The flesh was more efficiently pigmented in rainbow trout than in sea trout. Astaxanthin and canthaxanthin were deposited to the same extent when fed in a mixture. Astaxanthin dipalmitate was deposited in the flesh as free astaxanthin and more slowly than canthaxanthin, resulting in enhanced canthaxanthin deposition with diet ii. High values for apparent digestibility of the carotenoids were found but this was partly ascribed to breakdown of the carotenoids in the intestine or faeces. Analysis of the optical isomers of astaxanthin in the flesh demonstrated an increased level of (3 R ,3′ R )-astaxanthin and a reduced level of (3 S ,3′ S )-astaxanthin in both rainbow trout and sea trout fed the diet containing astaxanthin dipalmitate.

Carotenoids in diets for salmonids. III: Utilization of canthaxanthin from dry and wet diets by atlantic salmon, rainbow trout and sea trout

Abstract Yearlings of Atlantic salmon ( Salmo salar L.), rainbow trout ( Salmo gairdneri Richardson) and sea trout ( Salmo trutta L.) were fed to excess with dry and wet diets containing canthaxanthin for 14 months. The fish were maintained in sea-pens at four different experimental stations along the West coast of Norway. Fish were sampled at intervals of 2–3 months, and the carotenoid composition of flesh from the tail sections was analysed. Rainbow trout was the most efficiently pigmented when pigmentation was related to feeding period, while sea trout was the most efficiently pigmented in relation to fish growth. Salmon utilized canthaxanthin least efficiently in both cases. The extent of pigmentation varied according to geographical location, decreasing from the southern to the northern localities. The wet diet resulted in a lower pigmentation than the dry one. No other carotenoids than canthaxanthin (administered) and astaxanthin (from external sources) were detected in the flesh. The relative amount of astaxanthin was greatest in the fish fed the wet diet.

Prasinoxanthin—a chemosystematic marker for algae

Abstract A new coccoid marine alga (clone Ω 48-23) contained chlorophylls a and b and carotenoids consisting of β,β-carotene (3% of total), β,e-carotene (1%), zeaxanthin (2%), neoxanthin (21%), two minor unknowns (2 + 2%) and prasinoxanthin (69%). Prasinoxanthin is identical with xanthophyll K, previously considered characteristic of prasinophytes. From spectroscopic and chemical evidence prasinoxanthin is assigned the structure (3′R,-6′R)-3,6,3′ trihydroxy-7,8-dihydro-γ,e-caroten-8-one, with tentative 3R,6R chirality from biogenetic considerations, thus representing the first algal carotenoid with a γ-end group. The structural relationship between prasinoxanthin and siphonaxanthin (ex Prasinophyceae and Siphonales) is discussed in chemosystematic terms.

Carotenoids in diets for salmonids: II. Epimerization studies with astaxanthin in Atlantic salmon

Abstract Atlantic salmon ( Salmo salar , L.), kept in sea pens were fed diets containing pure carotenoids. No significant preferential utilization of the (3 S ,3′ S ), (3R,3′ S ) or (3R,3′ R ) optical isomers of astaxanthin was observed. No epimerization occurred in the flesh at the chiral centres at C-3 and C-3′ in astaxanthin.

Natural occurrence of enantiomeric and Meso astaxanthin 7∗-crustaceans including zooplankton

Abstract 1. 1. The isomeric ratio of enantiomeric and meso astaxanthin (free and esterified) in the crustaceans Calanus finmarchicus, Euphausia superba, Thysanoessa inermis, Acanthephyra purpurea and Cancer pagurus is reported. 2. 2. The ratios observed in C. finmarchicus and T. inermis , both considered as important feed ingredients for wild salmon, are compatible with those reported by others for wild salmon and with recent evidence demonstrating that salmonids obtain the three optical isomers of astaxanthin from the diet. 3. 3. The origin of the three optical isomers of astaxanthin in zooplankton is discussed briefly.

Carotenoids from eucaryotic ultraplankton clones (Prasinophyceae)

Abstract Three new eucaryotic ultraplankton clones contained chlorophylls a and b and carotenoids consisting of β,e-carotene (1–6% of total), β,β-carotene (5–9%), (3 R ,3′ R )-zeaxanthin (0–6%) (3 S ,3′ S )-astaxanthin (0–17%), prasinoxanthin (50–65%, major) and neoxanthin (13–25%). One clone also produced two new minor carotenoids with saturated 7′,8′-bond shown to be 7′,8′-dihydroprasinoxanthin-4′,5′-epoxide (4′,5′-epoxy-3,6,3′-trihydroxy-7,8,4′,5′,7′,8′-hexahydro-γ,e-caroten-8-one, 4%) and the lactone uriolide (5,6-epoxy-3,3′-dihydroxy-5,6,7′,8′-tetrahydro-β-e-caroten-11′,19′-olide, 8%) by methods including extensive 1 H NMR spin decoupling and mass spectrometry. Chiralities are considered using CD and 1 H NMR. The pigment distribution pattern suggests a close relationship to certain members of the class Prasinophyceae.

Carotenoids in food chain studies. I: Zooplankton (Daphnia magna) response to a unialgal (Scenedesmus acutus) carotenoid diet, to spinach, and to yeast diets supplemented with individual carotenoids

1. 1. A detailed carotenoid analysis of unialgal cultures of Scenedesmus acutus, including mass [1H]NMR, CD and determination of optical purity by the carbamate method, is reported. 2. 2. The detailed carotenoid pattern of Daphnia magna, fed on Scenedesmus acutus as the sole source of nutrients, revealed the metabolic formation of echinenone, canthaxanthin, (2R)-2-hydroxy-echinenone, (2R)-2-hydroxycanthaxanthin and optically pure (3S,3′S)-astaxanthin by D. magna. 3. 3. Feeding of carotenoid depleted D. magna on a yeast diet with canthaxanthin added as the single carotenoid was monitored by HPLC analysis and showed the metabolic conversion to 2-hydroxycanthaxanthin, but no increase in astaxanthin concentration. 4. 4. Feeding of D. magna with yeast supplemented with β,β-carotene, in direct comparison with a carotenoid-free yeast diet, revealed the conversion of β,β-carotene to echinenone, canthaxanthin, 2-hydroxyechinenone and 2-hydroxycanthaxanthin. 5. 5. It is concluded that D. magna in nature derives its ketocarotenoids echinenone, canthaxanthin, (2R)-2-hydroxyechinenone and (2R)-2-hydroxycanthaxanthin from β,β-carotene, selectively resorbed from the algal diet, whereas astaxanthin has a different metabolic origin. 6. 6. D. magna grown on spinach, revealed selective resorption of zeaxanthin. Carotenoid analysis of the spinach is reported. 7. 7. D. magna grown on yeast supplemented with synthetic (3R,3′R)-zeaxanthin converted zeaxanthin to astaxanthin. It is concluded that (3S,3′S)-astaxanthin in D. magna is metabolically derived from (3R,3′R)-zeaxanthin of algal origin.

Metabolism of carotenoids in salmonids—I. idoxanthin, a metabolite of astaxanthin in the flesh of atlantic salmon (Salmon salar, L.) under varying external conditions

Abstract 1. 1. Idoxanthin (3,3′,4′-trihydroxy-β,β-caroten-4-one) was found to be a metabolite of astaxanthin (3,3′-di-hydorxy-β,β-carotene-4,4′-dione) in Atlantic salmon. Idoxanthin was characterized by TLC, HPLC, VIS 1 H-NMR and MS. 2. 2. In experimental fish reared indoors in tanks, an increased formation and deposition of this metabolite in flesh was noticed, presumably as a result of stress. 3. 3. In farmed salmon kept in net cages in the open sea, idoxanthin was also found after one year of pigmentation, but had disappeared completely after two years when the fish had reached market size. 4. 4. Only minute amounts of idoxanthin were found in the flesh of wild Atlantic salmon comparable weights. 5. 5. Cofigurational and biochemical aspects of idoxanthin formation are discussed.