As a well-known carotenoid, Astaxanthin has many of the metabolic and physiological functions attributed to carotenoids, like b-carotene, zeaxanthin and lutein. The presence of the hydroxyl and keto endings on each ionone ring, explains some unique features. Astaxanthin has several essential biological functions including protection against oxidation of essential polyunsaturated fatty acids; protection against UV light effects and immune response. It is why astaxanthin has important applications in the nutraceutical, cosmetics, food and feed industries.