Isolation and Identification of 9-cis Astaxanthin by HPLC, FT-IR, and NMR Spectra

This study aims to perform a detailed qualitative analysis of astaxanthin isomers. A rapid, open column chromatography method was developed to separate astaxanthin geometrical isomers in gram-scale levels. Chromatographic separation was performed using two silica gel columns with dichloromethane/n-hexane/diethyl ether (2:1:1, v/v/v) as elution system. The isolated isomers were identified as all-trans, 9-cis, 13-cis, and 15-cis astaxanthin, according to previously reported C-30 high-performance liquid chromato graphy (HPLC) analysis data. Further, the fine structure of the single 9-cis astaxanthin isomer, as well as all-trans astaxanthin, was determined successfully for the first time by Fourier-transform infrared spectroscopy (FT-IR), one-dimensional H-1 and C-13 nuclear magnetic resonance (NMR) spectroscopy, and two-dimensional homonuclear correlation and heteronuclear correlation NMR spectroscopy.

Automated summary

This study aimed to perform a detailed qualitative analysis of astaxanthin isomers by developing a rapid open column chromatography method. The method successfully separated and identified several astaxanthin geometrical isomers. By utilizing HPLC analysis and various spectroscopic techniques, the fine structure of individual astaxanthin isomers was determined for the first time.