title: Fatty acids attached to all-trans-astaxanthin alter its cis-trans equilibrium, and consequently its stability, upon light-accelerated autoxidation.
abstract: 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 60min 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.
authors.affiliation: Wageningen University, Laboratory of Food Chemistry, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Wouter J C
authors.initials: WJ
authors.lastname: de Bruijn
authors.affiliation: Wageningen University, Laboratory of Food Chemistry, P.O. Box 17, 6700 AA Wageningen, The Netherlands; FeyeCon Carbon Dioxide Technologies, Rijnkade 17a, 1382 GA Weesp, The Netherlands.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Weesepoel
authors.affiliation: Wageningen University, Laboratory of Food Chemistry, P.O. Box 17, 6700 AA Wageningen, The Netherlands. Electronic address: jean-paul.vincken@wur.nl.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Vincken
authors.affiliation: Wageningen University, Laboratory of Food Chemistry, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Harry
authors.initials: H
authors.lastname: Gruppen
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005227:Fatty Acids / Q000737:chemistry*; D013058:Mass Spectrometry; D024341:Xanthophylls / Q000737:chemistry
chemical_list: D005227:Fatty Acids; D024341:Xanthophylls; C005948:astaxanthine
keywords: Astaxanthin; Autoxidation; Degradation; Fatty acid esterification; Stability; UHPLC–PDA–ESI-MS