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, fat/oil-soluble pigment. Astaxanthin can be found in microalgae, yeast, salmon, trout, krill, shrimp, crayfish, crustaceans, and the feathers of some birds. Currently, the primary natural source for astaxanthin is haematococcus pluvialis (microalge). It seems to accumulate the highest levels of astaxanthin in nature; commercially more than 40 g of astaxanthin per kilo of dry biomass. The commercial production of astaxanthin comes from both natural and synthetic sources. Synthetic astaxanthin fetches $2000 a kilogram on the market, while the natural product is sold for over $7000 a kilo.

Astaxanthin, unlike some carotenoids, does not convert to Vitamin A (retinol) in the human body. Too much Vitamin A is toxic for a human, but astaxanthin is not. While astaxanthin is a natural nutritional component, it can be found as a food supplement. The supplement is intended for human, animal, and aquaculture consumption. Astaxanthin has 100-500 times the antioxidant capacity of Vitamin E and 10 times the antioxidant capacity of beta-carotene. Many laboratory studies also indicate astaxanthin is a stronger antioxidant than lutein, lycopene and tocotrienols. Currently, the primary use for humans is as a food supplement. Research shows that due to astaxanthin's potent antioxidant activity, it may be beneficial in cardiovascular, immune, inflammatory and neurodegenerative diseases. Research supports the assumption that it protects body tissues from oxidative damage

The primary use of synthetic astaxanthin today is as an animal feed additive to impart coloration, this includes farm-raised salmon and egg yolks. In that, synthetic carotenoid (i.e., coloured yellow, red or orange) pigments represent about 15-25% of the cost of production of commercial salmon feed. The class action lawsuits were filed against some major grocery store chains for not clearly labeling the salmon "color added". The chains follow up quickly by labeling all such salmon as "color added".

Formal Chemical Name (IUPAC)
(6S,6'S)-3,3'-((1E,3E,5E,7E,9E,11E,13E,15E,17E)-3,7,12,16-tetramethyloctadeca-1,3,5,7,9,11,13,15,17-nonaene-1,18-diyl)bis(6-hydroxy-2,4,4-trimethylcyclohex-2-enone)

References

http://en.wikipedia.org/wiki/Astaxanthin

http://www.nationmaster.com/encyclopedia/E161j