Astaxanthin (3,3’-dihydroxy-β-β-carotene-4,4’-dione ) is a carotenoid, commonly found in marine environments. The presence of the hydroxyl and keto endings on each ionone ring (Figure below), explains some unique features of Astaxanthin, such as its ability to be esterified, its high anti-oxidant potency and a more polar configuration than other carotenoids. Free Astaxanthin is extremely sensitive to oxidation, however its esterified form, as found in nature in the Haematococcus pluvialis (H. pluvialis) microalga, is stable and displays higher bioavailability and potency (Odberg 2003, Rufer 2008, Barbossa 1999).