Astaxanthin

Astaxanthin (pronounced /æstəˈzænθɨn/) 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. ^[4][5] 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.^[6]

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.^[7] The European Commission considers it food dye and it is given the E number E161j.^[8] Natural astaxanthin is considered generally recognized as safe (GRAS) by the FDA,^[9][10] but as a food coloring in the United States it is restricted to use in animal food.^[11]

Natural sources

The following sources are used for the commercial production of astaxanthin:

• Euphausia pacifica (Pacific krill)
• Euphausia superba (Antarctic krill)
• Haematococcus pluvialis (MicroAlgae)
• Pandalus borealis (Arctic shrimp)
• Xanthophyllomyces dendrorhous, formerly Phaffia rhodozyma (yeast)

As a natural source, the following can be found in nature (or a production facility) with the approximate astaxanthin concentrations:

Currently, the primary natural source for astaxanthin is the microalgae Haematococcus pluvialis.^[13] It seems to accumulate the highest levels of astaxanthin in nature;^[14] Commercially more than 40 g of astaxanthin can be obtained from one kg of dry biomass.^[15] 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.^[16]

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.^[17]

For obtaining astaxanthin from Euphausia superba (Antarctic krill), there are a number of issues:^[18]

The Krill fishing operation is complex. It is done in Antarctic waters, under extreme weather conditions and far away from ports with substantial operational complexities. Krill's fishing location and the difficult weather conditions in the main fishing area, together with the costs involved in the operation, have contributed to a slow development of the industry. Krill fishing is by far different than any other fishing operation today known. The knowledge to work with it belongs to very few people in the world.

However, In recent years, the ocean krill population has become threatened due to commercial demands, which has created a sustainability problem.

Astaxanthin is commercially collected from shrimp processing waste. 12,000 pounds of wet shrimp shells can yield a 6-8 gallon astaxanthin/triglyceride oil mixture.^[19]

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.^[15] 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.^[16] Synthetic astaxanthin fetches $2000 per kg, while the natural product is sold for over $7000 per kg.^[20]

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.^[21] 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.^[22]

Difference between natural and synthetic forms

Astaxanthin has two chiral centers, at the 3 and 3' positions. Therefore, there are three stereoisomers; (3-R,3'-R), (3-R,3'-S) (meso), and (3-S,3'-S). Synthetic astaxanthin contains a mixture of the three, in approximately 1:2:1 proportions. Naturally occurring astaxanthin varies considerably from one organism to another. The astaxanthin in fish is of whatever stereoisomer the fish ingested.^[23] The astaxanthin produced by haematococcus pluvialis, which is commonly used in the feed of animals that are in turn consumed by humans, is the (3-S,3'-S) stereoisomer.^[16]

Uses

Astaxanthin is used as a feed supplement for salmon, crabs, shrimp, chickens and egg production.^[24] Regardless of the source, astaxanthin provides some important benefits beyond coloration. It also has been found to be essential for proper growth and survival.^[15]

For seafood and animals

The primary use of synthetic astaxanthin today is as an animal feed additive to impart coloration, including farm-raised salmon and egg yolks.^[15] Synthetic carotenoid pigments colored yellow, red or orange represent about 15–25% of the cost of production of commercial salmon feed.^[25] Today, almost 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.^[15] 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.^[26]

The farm-raised salmon lawsuit

Class action lawsuits have been filed against some major grocery store chains for not clearly labeling the salmon "color added".^[26] The chains followed up quickly by labeling all such salmon as "color added". "However, Smith & Lowney persisted with the suit for damages, but a Seattle judge dismissed (...)(the case), ruling that enforcement of the applicable food laws was up to government and not individuals."^[27]

For humans

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.^[28] While it does function as a carotenoid antioxidant, research has shown that lycopenes are more efficient antioxidants than carotenoids.^[6] Some research has suggested potential as an anti-cancer agent.^[29] Some research supports the assumption that it may protect body tissues from oxidative damage.^[30]

Role in the food chain

It has been speculated that gulls are "flushed" pink when molting, especially in areas with farm-raised salmon.^[31] However, not enough is known about the relationship between astaxanthin and plumage.^[32] For example, cardinals seem to produce astaxanthin from carotenoids when molting, even when fed primarily seed with natural yellow dye.^[33]

Lobsters, shrimp, and some crabs turn red when cooked because the astaxanthin, which was bound to the protein in the shell, becomes free as the protein denatures and unwinds. The freed pigment is thus available to absorb light and produce the red color. ^[34]

Regulations

In April 2009, the US FDA approved astaxanthin as an additive for fish feed only as a component of a stabilized color additive mixture. Color additive mixtures for fish feed made with astaxanthin may contain only those diluents that are suitable.^[7] The color additives astaxanthin, ultramarine blue, canthaxanthin, synthetic iron oxide, dried algae meal, Tagetes meal and extract, and corn endosperm oil are approved for specific uses in animal foods.^[35] Haematococcus algae meal (21 CFR 73.185) and Phaffia yeast (21 CFR 73.355) for use in fish feed to color salmonoids were added in 2000.^[36][37][38] In the European Union, astaxanthin-containing food supplements derived from sources that 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 that 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.^{[39][40][41][42]}

References

External links

• Astaxanthin — Frequently Asked Questions
• AstaFactor Technical Report Haematococcus Pluvialis and Astaxanthin Safety For Human Consumption
• Articles on Astaxanthin See reference table for a large well researched list of articles.
• aquafeed.com Natural Foods through marine Krill Meal — 09/09/2003
• Development of microalgal pigments for aquaculture in Europe; Final Report, February, 2001.
• Study of the expression of carotenoid biosynthesis genes in wild-type and deregulated strains of Xanthophyllomyces dendrorhous (Ex.: Phaffia rhodozyma).
• Multibudding in Xanthophyllomyces dendrorhous Cells Under Hydric and Nitrogen Stress [1]
• The Effects of Three Carotenoid Sources on Growth and Pigmentation of Juvenile Freshwater Crayfish Cherax quadricarinatus
• Astaxanthin for aquaculture — Carophyll Pink since 1985
• Aquasta: Naturally-sourced astaxanthin from Phaffia Yeast
• http://www.aquafeed.com/article.php?id=365