What is Astaxanthin? Astaxanthin (asta-zan-thin) is one of the most powerful antioxidants found in nature. It naturally occurs in some seafood (salmon, krill, shrimp), especially those with reddish/orange flesh, since it is a pigment-based form of carotenoid. As a supplement, Astaxanthin is isolated from a marine microalgae (Haemotoccus Pluvialis). Astaxanthin, unlike most antioxidants, is both fat and water soluble, which makes it more powerful than vitamin C (water soluble) or CoQ10 (fat soluble) at scavenging free radicals.