Identification of Geometrical Isomers and Comparison of Different Isomeric Samples of Astaxanthin
Article first published online: 17 AUG 2012
© 2012 Institute of Food Technologists®
Journal of Food Science
Volume 77, Issue 9, pages C934–C940, September 2012
How to Cite
Qiu, D., Wu, Y.-C., Zhu, W.-L., Yin, H. and Yi, L.-T. (2012), Identification of Geometrical Isomers and Comparison of Different Isomeric Samples of Astaxanthin. Journal of Food Science, 77: C934–C940. doi: 10.1111/j.1750-3841.2012.02842.x
- Issue published online: 7 SEP 2012
- Article first published online: 17 AUG 2012
- MS 20120157 Submitted 2/1/2012, Accepted 4/23/2012.
- isomer; melting;
Abstract: A high-performance liquid chromatographic (HPLC) analysis system for isomeric astaxanthin was developed. The separation system consisted of a C30 column and an elution system of methanol/MTBE/water/dichloromethane (77 : 13 : 8 : 2, v/v/v/v). Using the combination of HPLC diode array detector and HPLC atmospheric pressure chemical ionization mass spectrometry, 11 geometrical isomers and 4 epoxides of astaxanthin were successfully identified. Referred to crystal, only isomerization with different degrees was found for solvent dissolving and iodine catalysis, while melting of astaxanthin caused isomerization, slight oxidation, and more noticeable polymerization confirmed by gel permeation chromatography. Chemical changes in isomeric samples all caused a decrease in UV content. The vibrational spectra (infrared and Raman) showed that epoxide was the only new functional group generated for melting. Changes of several key bands and formations of new bands were found in iodine catalysis and melting samples because of isomerization.
Practical Application: Eleven geometrical isomers and 4 epoxides, which were normally generated for solvent dissolving, iodine catalysis, and melting of astaxanthin, have been identified by C30-HPLC-MS technology. Furthermore, different samples were measured by gel permeation chromatography, UV, infrared, and Raman, based on the analysis of messages, the effect of each processing was well understood.