<i>trans/cis</i> Isomerization of Astaxanthin Diacetate/Isolation by HPLC. and Identification by ¹H‐NMR. Spectroscopy of Three Mono‐<i>cis</i>‐ and Six Di‐<i>cis</i>‐Isomers

Abstract

Abstract Thermal and iodine‐catalyzed photochemical trans/cis isomerization of synthetic, racemic astaxanthin diacetate (3,3′‐dihydroxy‐β,β‐carotene‐4,4′‐dione diacetate) yielded multi‐component mixtures of cis ‐isomers. Separation and isolation of 10 different cis ‐isomers in quantities between 10 and 70 μg was achieved by HPLC. Investigation of their 270‐MHz‐FT‐ 1 H‐NMR. spectra led to the identification of 9 of these isomers, namely the 9‐, 13‐, and 15‐mono‐ cis ‐, the 9,9′‐, 9,13‐, 9,13′‐, 9,15‐, 13,13′‐, and 13,15‐di‐ cis ‐astaxanthin diacetate.