Influence of molecular structure of astaxanthin esters on their stability and bioavailability

The stability and bioavailability of fourteen astaxanthin esters (Asta-Es) with different molecular structures were investigated using in vitro and in vivo digestion models. The results demonstrated that Asta-E with long-chain and saturated fatty acids were more stable than other types of Asta-E. Astaxanthin diester (Asta-DE) was better than astaxanthin monoester (Asta-ME) and free astaxanthin (F-Asta), as determined based on the degradation rate constant at 60 °C. The absorbability of Asta-Es with different molecular structures was evaluated through the serum concentrations of astaxanthin (Asta). The results indicated that Asta-E with short-chain fatty acids had higher bioavailability than Asta-Es with long-chain fatty acids, whereas Asta-E with high-unsaturation fatty acids had higher bioavailability than Asta-E with low-unsaturation fatty acids. Asta-ME had significantly increased bioavailability compared with Asta-DE. We concluded that the molecular structure of Asta-E could significantly affect their stability and bioavailability.