Identification of geometrical isomers and comparison of different isomeric samples of astaxanthin.
A high-performance liquid chromatographic (HPLC) analysis system for isomeric astaxanthin was developed. The separation system consisted of a C(30) 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 C(30) -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.
College of Chemical Engineering, Ningbo Univ of Technology, 89 Cuibai Road, Ningbo 315016, PR China. qiudan_zju@163.com
Dan
D
Qiu
Yue-Chan
YC
Wu
Wen-Li
WL
Zhu
Hong
H
Yin
Long-Tao
LT
Yi
D001274:Atmospheric Pressure; D002850:Chromatography, Gel / Q000379:methods; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004852:Epoxy Compounds / Q000378:metabolism; D007536:Isomerism; D013058:Mass Spectrometry / Q000379:methods; D012997:Solvents; D013059:Spectrum Analysis, Raman / Q000379:methods; D024341:Xanthophylls / Q000737:chemistry / Q000302:isolation & purification
D004852:Epoxy Compounds; D012997:Solvents; D024341:Xanthophylls; C005948:astaxanthine