Purification of trans-astaxanthin from a high-yielding astaxanthin ester-producing strain of the microalga Haematococcus pluvialis

The purification method including extraction, saponification, and separation was established for preparing free trans-astaxanthin from a high-yielding astaxanthin ester-producing strain of the microalga Haematococcus pluvialis which contained 3.67% trans-astaxanthins and 1.35% cis-astaxanthins of the dry cells. Low temperature (5 degrees C) was chosen to minimize the degradation of astaxanthins during saponification, and 94.4% free trans-astaxanthin was obtained from Irans-astaxanthin esters after 12 h of saponification. With this method, 32.2 mg trans-astaxanthin was obtained from 1 g dry algal cells. In addition, a new gradient reversed-phase HPLC method, suited for the quick analysis of free astaxanthins and astaxanthin esters in the unsaponified and saponified pigment extracts from the high-yielding astaxanthin ester-producing strain of the microalga Haematococcus pluvialis, was developed and applied to the determination of astaxanthin contents during the processes of extraction, saponification, and purification. (C) 2000 Elsevier Science Ltd. All rights reserved.