concentrations in human plasma than all-E-astaxanthin in reported studies. All three astaxanthin isomers were effective in maintaining cellular redox homeostasis as seen in the antioxidant enzyme (CAT, SOD) activities ; 9Z- and 13Z- astaxanthins exhibited a higher protective effect than all-E-astaxanthin against oxidative stress as demonstrated by the lower cellular uptake of Z-astaxanthins and lower secretion
The effect of oral supplementation with astaxanthin of different Z-isomer ratios on ultraviolet (UV) light-induced skin damage in guinea pigs was investigated. Astaxanthin with a high Z-isomer content was prepared from the all-E-isomer via thermal isomerization. Intact (all-E)-astaxanthin and the prepared Z-isomer-rich astaxanthin were suspended in soybean oil and fed to guinea pigs for three weeks
Rapid and Efficient Conversion of All-<i>E</i>-astaxanthin to 9<i>Z</i>- and 13<i>Z</i>-Isomers and Assessment of Their Stability and Antioxidant Activities
An optimized isomerization method was developed by heating all-E-astaxanthin in ethyl acetate (70 degrees C) with I-TiO2 catalyst, yielding 22.7% and 16.9% of 9Z- and 13Z-astaxanthin, respectively, in 2 h, with 92-95% purity after semipreparative HPLC purification. 13Z-Astaxanthin had higher antioxidant activity than all-E- and 9Z-astaxanthins in oxygen radical absorbing capacity assay for lipophilic compounds, photochemiluminescence, and cellular antioxidant activity (CAA) assays, and 9Z-astaxanthin was higher in DPPH radical-scavenging activity assay and lower in CAA assay. All isomers were relatively stable between pH 2.0 and 11.6, except 13Z- and 9Z-astaxanthins at pH 2.0, suggesting they may be converted after passing the gastric phase in vivo. Metal ions did not significantly (p < 0.05) affect the stability. Results of the current study provides a means for further study into the mechanisms related to in vivo transformation and bioavailability of Z-astaxanthins, and their application in the development of functional foods and nutraceutical products.
Isomer Separation of trans-Astaxanthin, 9-cis-Astaxanthin and 13-cis-Astaxanthin by Ligand Exchange Chromatography
作者:Yu Ri Lee、Xiaoxia Li、Kyung Ho Row
DOI:10.14233/ajchem.2016.19547
日期:——
The astaxanthin molecule has two geometric isomers, cis or trans on account of the double bond from the polyene chain. The separation of these isomers is quite difficult using ordinary techniques. The conditions of ligand exchange chromatography for stereoisomer separation were examined using an astaxanthin stereoisomer. A C18 column was used with a mobile phase consisting of an acetonitrile-chloroform-methanol chiral mobile phase additive solution (containing different concentrations of L-serine and copper sulfate) at flow rate of 0.5 mL/min. The effects of different kinds and concentrations of ligands, bivalent ligand ions and organic modifier were evaluated. The astaxanthin isomers could be obtained from heat-treating the astaxanthin standard, which were confirmed by the ultraviolet-visible and nuclear magnetic resonance spectroscopy.