Z-Isomers of Astaxanthin Exhibit Greater Bioavailability and Tissue Accumulation Efficiency than the All-E-Isomer

The purpose of the present study was to clarify the differences in the bioavailability and tissue accumulation efficiency between (all- E )- and ( Z )-astaxanthin. Astaxanthin with a high proportion of the Z -isomer (especially rich in the 9 Z - and 13 Z -isomers) was prepared from (all- E )-astaxanthin by thermal treatment and solid–liquid separation. The all- E -isomer- or Z -isomer-rich diet was fed to male rats for 2 weeks. After the feeding period, blood and tissue samples were collected, and their astaxanthin levels were evaluated. The Z -isomer-rich astaxanthin diet resulted in higher levels of astaxanthin in blood and many tissues (in particular, skin, lung, prostate, and eye) compared to the all- E -isomer-rich diet. Moreover, the Z -isomer-rich diet enhanced the level of the 13 Z -isomer in blood and tissues rather than that of the 9 Z -isomer. These results strongly supported that astaxanthin Z -isomers have greater bioavailability and tissue accumulation efficiency than the all- E -isomer. Moreover, (13 Z )-astaxanthin would have higher bioavailability and tissue accumulation than the other isomers.