Astaxanthin is a carotenoid. It belongs to a larger class of phytochemicals known as terpenes. It is classified as a xanthophyll, which means "yellow leaves". Like many carotenoids, it is a colorful, lipid-soluble pigment. Astaxanthin is found in microalgae, yeast, salmon, trout, krill, shrimp, crayfish, crustaceans, and the feathers of some birds. Professor Basil Weedon was the first to map the structure of astaxanthin.
Astaxanthin, unlike some carotenoids, is not converted to vitamin A (retinol) in the human body. Too much vitamin A is toxic for a human, but astaxanthin has lower toxicity. It is an antioxidant with a slightly lower antioxidant activity than other carotenoids.
While astaxanthin is a natural nutritional component, it can also be used as a food supplement. The supplement is intended for human, animal, and aquaculture consumption. The commercial production of astaxanthin comes from both natural and synthetic sources.
The U.S. Food and Drug Administration (FDA) has approved astaxanthin as a food coloring (or color additive) for specific uses in animal and fish foods. The European Commission considers it food dye and it is given the E number E161j. Natural astaxanthin is considered generally recognized as safe (GRAS) by the FDA, but as a food coloring in the United States it is restricted to use in animal food.
Nearly all commercial astaxanthin for aquaculture is produced synthetically, with an annual turnover of over $200 million and a selling price of ~$2000 per kilo. However, synthetic production of astaxanthin is not preferred in some cases because synthetic astaxanthin contains a mixture of stereoisomers. Astaxanthin is fairly abundant and obtainable from natural sources, and some consumers prefer natural products over synthetic ones. Synthetic astaxanthin fetches $2000 per kg, while the natural product is sold for over $7000 per kg.
An efficient synthesis from isophorone, cis-3-methyl-2-penten-4-yn-1-ol and a symmetrical C10-dialdehyde has been discovered and is used commercially. It combines these chemicals together with an ethynylation and then a Wittig reaction. Two equivalents of the proper ylide combined with the proper dialdehyde in a solvent of methanol, ethanol, or a mixture of the two, yields astaxanthin in up to 88% yields.
Astaxanthin is used as a feed supplement for salmon, crabs, shrimp, chickens and egg production. Regardless of the source, astaxanthin provides some important benefits beyond coloration. It also has been found to be essential for proper growth and survival.
The primary use of synthetic astaxanthin today is as an animal feed additive to impart coloration, including farm-raised salmon and egg yolks. Synthetic carotenoid pigments colored yellow, red or orange represent about 15-25% of the cost of production of commercial salmon feed. Today, essentially all commercial astaxanthin for aquaculture is produced synthetically from petrochemical sources, with an annual turnover of over $200 million, and a selling price of ~$2000 per kilo of pure astaxanthin. While it constitutes a tiny portion of salmon feed (50 to 100 parts per million), astaxanthin represents a major share of the cost, up to 20 percent.
In the European Union, astaxanthin-containing food supplements derived from sources which have no history of use as a source of food in Europe, fall under the remit of the Novel Food legislation, EC (No.) 258/97. Since 1997, there have been five novel food applications concerning products which contain astaxanthin extracted from these novel sources. In each case, these applications have been simplified or substantial equivalence applications, because astaxanthin itself is recognised as a food component in the EU diet.