# STUDIES ON THE METABOLISM OF ASTAXANTHIN IN THE RAINBOW TROUT (SALMO GAIRDNERI)

#### Abstract

Racemic astaxanthin was fed to rainbow trout (Salmo gairdneri) for 2, 4, and 6 weeks. The fish showed a bright pink coloration of the skin and flesh; the highest amount of astaxanthin (162 ug/100g) was found in the skin of fish fed the test diet for six weeks. Lutein, 3-epilutein, and zeaxanthin were also detected in the flesh and skin; it was concluded that astaxanthin was converted to zeaxanthin in the skin. The mean vitamin A content of the liver was determined; the ratio of vitamin A$\sb1$:vitamin A$\sb2$ was approximately 1:3. There was no significant difference in the vitamin A content of the control and experimental fish; this proves that astaxanthin was not functioning as a vitamin A precursor in vitamin-A-rich rainbow trout.^ Retinol and 3,4-dehydroretinol were extracted from the intestine of rainbow trout low in vitamin A, after force feeding with astaxanthin using a feeding tube. Antibiotic-treated fish had no marked difference in vitamin A content compared with a control group that received no antibiotic. This proves that astaxanthin was converted to vitamin A in fish depleted of vitamin A, that microorganisms were not involved in the conversion, and that conversion occurred in the intestine. An in vitro study using $\sp3$H 3S, 3S$\sp\prime$- astaxanthin incubated with duodenal and ileal segments of the intestine provided HPLC and radioisotope data, which showed that rainbow trout were able to bioconvert astaxanthin to vitamin A. The results confirmed earlier observations. ^

#### Subject Area

Agriculture, Animal Culture and Nutrition|Agriculture, Fisheries and Aquaculture

#### Recommended Citation

ABDULRHMAN SALIH AL-KHALIFAH, "STUDIES ON THE METABOLISM OF ASTAXANTHIN IN THE RAINBOW TROUT (SALMO GAIRDNERI)" (1986). Dissertations and Master's Theses (Campus Access). Paper AAI8715321.
http://digitalcommons.uri.edu/dissertations/AAI8715321

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