Rapid and Efficient Conversion of All-E-astaxanthin to 9Z- and 13Z-Isomers and Assessment of Their Stability and Antioxidant Activities

J Agric Food Chem. 2017 Feb 1;65(4):818-826. doi: 10.1021/acs.jafc.6b04962. Epub 2017 Jan 19.


An optimized isomerization method was developed by heating all-E-astaxanthin in ethyl acetate (70 °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.

Keywords: 13Z-astaxanthin; 9Z-astaxanthin; all-E-astaxanthin; antioxidant activity; isomerization; metal ion; pH effect; semipreparative purification; stability.

MeSH terms

  • Antioxidants / chemistry*
  • Isomerism
  • Molecular Structure
  • Oxidation-Reduction
  • Xanthophylls / chemistry


  • Antioxidants
  • Xanthophylls
  • astaxanthine