|Title||Fatty acids attached to all-trans-astaxanthin alter its cis-trans equilibrium, and consequently its stability, upon light-accelerated autoxidation|
|Author(s)||Bruijn, Wouter J.C. De; Weesepoel, Y.; Vincken, J.P.; Gruppen, H.|
|Source||Food Chemistry 194 (2016). - ISSN 0308-8146 - p. 1108 - 1115.|
Food Chemistry Group
|Publication type||Refereed Article in a scientific journal|
Fatty acid esterification, common in naturally occurring astaxanthin, has been suggested to influence both colour stability and degradation of all-trans-astaxanthin. Therefore, astaxanthin stability was studied as influenced by monoesterification and diesterification with palmitate. Increased esterification decelerated degradation of all-trans-astaxanthin (RP-UHPLC-PDA), whereas, it had no influence on colour loss over time (spectrophotometry). This difference might be explained by the observation that palmitate esterification influenced the cis-trans equilibrium. Free astaxanthin produced larger amounts of 9-cis isomer whereas monopalmitate esterification resulted in increased 13-cis isomerization. The molar ratios of 9-cis:13-cis after 60 min were 1:1.7 (free), 1:4.8 (monopalmitate) and 1:2.6 (dipalmitate). The formation of 9-cis astaxanthin, with its higher molar extinction coefficient than that of all-trans-astaxanthin, might compensate for colour loss induced by conjugated double bond cleavage. As such, it was concluded that spectrophotometry is not an accurate measure of the degradation of the all-trans-astaxanthin molecule.