Overview Astaxanthin is a naturally occurring carotenoid found in various marine organisms, including microalgae, yeast, salmon, trout, krill, shrimp, crayfish, and crustaceans. This powerful antioxidant belongs to a larger class of chemical compounds known as terpenes. Astaxanthin is known for its vibrant red-orange pigment and is responsible for the pinkish color in salmon and shrimp.