Effect of esterification on the absorption of astaxanthin in rainbow trout, Oncorhynchus mykiss (Walbaum)

Abstract

Gastrointestinal and serum absorption of astaxanthin was studied in rainbow trout, Oncorhynchus mykiss (Walbaum) (217 +/- 2 g) fed diets supplemented with either esterified astaxanthin (from Haematococcus pluvialis) or free astaxanthin (synthetic, as 8% w/w beadlets) at similar levels (50 mg kg(-1)). After 56 days of feeding, there was a significant difference (P=0.0582) between steady-state serum astaxanthin concentrations for fish fed free (2.0 +/- 0.3 microgram mL(-1)) or esterified astaxanthin (1.3 +/- 0.1 microgram mL(-1)) at the 90% confidence level. However, following ingestion of a single meal supplemented with free or esterified astaxanthin, the rates of astaxanthin absorption into serum were not significantly different (P > 0.1) (0.8 +/- 0.2 microgram mL(-1) h(-1) and 1.0 +/- 0.4 microgram mL(-1) h(-1) respectively). In fish fed both free or esterified astaxanthin, higher absorption (P < 0.05) of astaxanthin by the ileal (0.8 +/- 0.14 microgram g(-1) and 0.9 +/- 0.15 microgram g(-1) respectively) compared with the posterior (0.2 +/- 0.01 microgram g(-1) and 0.3 +/- 0.14 microgram g(-1) respectively) intestine was recorded. This confirmed the role of the anterior intestine in carotenoid absorption. Non-detectable levels of esters in digesta taken from the hind intestine suggest the anterior intestine is also the primary region for ester hydrolysis.