Identification of astaxanthin isomers in Haematococcus lacustris by HPLC-photodiode array detection

Abstract

An HPLC method was developed for the separation and identification of the isomers of astaxanthin from the saponification products of the individual astaxanthin ester fractions and the total pigment extract from Haematococcus lacustris. Six astaxanthin ester fractions were initially separated and collected by HPLC. These astaxanthin ester fractions and the total pigment extract were subsequently respectively hydrolysed. Four isomers of astaxanthin in the saponified mixtures were separated and identified respectively as (3S, 3'S)-trans-astaxanthin (478.8 nm), (3S, 3'S)-9-cis-astaxanthin (470.4 nm), (3S, 3's)13-cis-astaxanthin (371.8 and 468.0 nm) and (3R, 3'R)-trans-astaxanthin (477.6 nm) according to their absorbance spectra and absorption maxima by photodiode array detection. The relative contents of these isomers were determined to be 72.8, 9.7, 8.9 and 8.6%, respectively, in Haematococcus lacustris.