Metabolism of three stereoisomers of astaxanthin in the fish, rainbow trout and tilapia

Abstract

1. 1. In rainbow trout ( Salmo gairdneri), the dietary astaxanthin diesters were mostly absorbed and accumulated in their integuments keeping their configurations, and partially metabolized to (3R,3′R)-zeaxanthin (major) and/or (3R,3′S)-zeaxanthin (medium) and/or (3S,3′S)-zeaxanthin (minor). 2. 2. In tilapia ( Tilapia nilotica), the three stereoisomers of astaxanthin diesters were promptly metabolized to only (3S,3′S)-astaxanthin, and subsequently to (3R,3′R)-zeaxanthin and/or (3R,3′S)-zeaxanthin and/or (3S,3′S)-zeaxanthin at an invariable ratio, 4:1:0.3. 3. 3. The above facts indicate that the conversion from 3S- to 3R-configuration was carried out in vivo, and vice versa, and that astaxanthins were reductively metabolized to zeaxanthins in both the fish.