Preparative isolation and characterization of some minor impurities of astaxanthin by high-performance liquid chromatography

A simple and rapid preparative high-performance liquid chromatography (HPLC) method has been developed to isolate and characterize some minor impurities of astaxanthin using a normal-phase Lichrosorb silica column with n-hexane–acetone–tetrahydrofuran (90:2:8, v/v/v) as mobile-phase and detection at 475 nm. The isolated impurities were characterized as astacene, dehydro astacene and apoastaxanthinal by UV–vis, ESI–MS, 1H and 13C NMR spectroscopy and the molecular structures were assigned. The impurities collected using the developed conditions were over 98% pure.