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. It provides the red color of salmon meat and cooked shellfish. 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.
Natural sources :
Euphausia pacifica (Pacific krill)
Euphausia superba (Antarctic krill)
Haematococcus pluvialis (MicroAlgae)
Pandalus borealis (Arctic shrimp)
Xanthophyllomyces dendrorhous, formerly Phaffia rhodozyma (yeast)
Currently, the primary natural source for astaxanthin is the microalgae Haematococcus pluvialis. It seems to accumulate the highest levels of astaxanthin in nature. Commercially more than 40 g of astaxanthin can be obtained from one kg of dry biomass. It has the advantage
of the population doubling every week, which means scaling up is not an issue. However, it does require some expertise to grow the algae with a high astaxanthin content. Specifically, the microalgae is grown in two phases. First, in the green phase, the cells are given an abundance of nutrients to promote proliferation of the cells. In the subsequent red phase, the cells are deprived of nutrients and subjected to intense sunlight to induce encystment (carotogenesis), during which the cells produce high levels of astaxanthin as a protective mechanism against the environmental stress. The cells, with their high concentrations of astaxanthin, are then harvested.
Phaffia yeast Xanthophyllomyces dendrorhous exhibits 100% free, non-esterified astaxanthin, which is considered advantageous because it is readily absorbable and need not be hydrolysed in the digestive tract of the fish. In contrast to synthetic and bacteria sources of astaxanthin, yeast sources of astaxanthin consist virtually all in 3R, 3’R form, an important astaxanthin source in nature. Finally, the geometrical isomer, all-E, is higher in yeast sources of astaxanthin, as compared to synthetic sources. This contributes to greater efficacy because the all-E (trans) isomer has greater bio-availability than the cis isomer.
Synthetic sources :
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.