all-trans-Astaxanthin is a ketocarotenoid, most commonly identified in marine and aquatic animals, including krill, wild salmon, rainbow trout, microalgae, shells of lobster, shrimp, seafood products, etc. It is biologically known as a vitamin A precursor, and exhibits strong antioxidant property, much higher compared to vitamin E and β-carotene. Its role in food and the medicinal industry is also well-defined.