Comparison of the Digestion and Absorption Characteristics of Docosahexaenoic Acid-Acylated Astaxanthin Monoester and Diester in Mice

Docosahexaenoic acid-acylated astaxanthin (DHA-AST) esters exhibit distinct bioactivities in improving brain function. However, the digestion and absorption characteristics of DHA-AST esters in vivo are unclear, thereby restricting the molecular mechanism analysis of their superior activities. This study compared the digestion and absorption characteristics of DHA-AST monoester and diester by determining the levels of AST and DHA in the serum, liver, small intestinal content and wall, and feces at different time points after a single-dose oral administration of the esters. After oral gavage with 2 mg AST equivalent of the DHA-AST monoester and diester for 18 h, the excretion rates were approximately 51% and 84%, respectively. This result indicates that DHA-AST monoester was better than diester for the absorption of AST. The results in serum, liver, and small intestinal content and wall also agreed with this finding. Moreover, the excretion rates of DHA in the feces at 24 h in the DHA-AST monoester and diester groups were approximately 40% and 36% after gavage with 5 mg DHA equivalent, respectively. This result indicates that DHA-AST diester exhibited a better tendency than monoester for the absorption of DHA. Interestingly, the results in the liver and small intestinal wall showed an apparent difference, indicating that DHA-AST diester was better than monoester for the absorption of DHA. These findings provide a scientific basis for the molecular mechanism analysis and utilization of DHA-AST monoester and diester as functional ingredients.