MX2011005264A - Method for the preparation of oxycarotenoids. - Google Patents

Abstract

A high-yield process for preparing astaxanthin (3,3'-dihydroxy-β, β- carotene-4, 4'- dione) from silylated derivatives of zeaxanthin (3,3'-dihydroxy-β, β- carotene-3, 3'-diol), whether it be of synthetic or natural origin, is described.

Description

Method for the Preparation of Oxycarotenoids Background Astaxanthin occurs naturally in various algae, bacteria, fungi and some animals, often forming some kind of complex with proteins; Also in plants such as Adonis annua L. and in some birds such as flamingos, quails, etc., it can also be chemically found in its free form or as a mono- or diesterified derivative.

Normally the amount of this carotenoid found in its natural sources is very limited, this is why commercially it has resorted to other additional natural sources such as krill, crustacean by-products, genetically modified marigold flowers and others. In addition, the use of astaxanthin isolated from extracts of flours of the yeast Phaffia rhodozyma and of the microalga Haematococcus pluvialis has also been increased. The microalgae Clorococcum sp. Has also been considered as an alternate source of astaxanthin as well as other carotenoids such as canthaxanthin and adonixanthin.

This carotenoid has generally been used for the pigmentation of some salmonids that do not synthesize de novo to which it confers the pink tones that the market prefers.

It has also found application in the pigmentation of crustaceans, although in these it is more appreciated its immunostimulant and antioxidant activity, which It has a marked impact on their health and, therefore, on better survival rates when they are intensively cultivated. Other carotenoids such as canthaxanthin, echinenone and adonixanthin are used for similar purposes.

It has recently been shown that astaxanthin exhibits antioxidant activity superior to that of most carotenoids (J. Agrie, Food Chem. 48, 150) and that it is currently used successfully for human consumption as well. The potent antioxidant activity of astaxanthin has been implicated with various biological roles demonstrated both in animal experiments and in clinical studies. Astaxanthin has then shown that it has a great potential for applications in human health and nutrition. The most important activities of astaxanthin in human health include its antioxidant and anti-inflammatory power, it prevents some types of cancer, it supports the immune system and vision, positive effects in arterial hypertension and in general in blood pressure, vascular dementia and heart attacks (J Nat Prod., 69,443).

For decades Astaxanthin has been obtained synthetically in the form of a racemic mixture of the isomers (3R, 3'R), (3R, 3'S) and (3S, 3'S) by companies such as DSM (ROCHE) and BASF using schemes long and expensive what has made this carotenoid one of the very expensive.

Synthetic astaxanthin is a molecule identical to that produced in some living organisms and consists of a 1: 2: 1 mixture of the isomers (3R, 3'R), (3R, 3'S) and (3S, 3'S) respectively.

However, it had already been announced since 1967 that astaxanthin was obtained from astacene (Chem Comm., 49) and dimethyl astaxanthin was also obtained by oxidizing zeaxanthin dimethyl ether (J. Org. Chem. , 32,180) in addition to the synthesis of astaxanthin from canthaxanthin using silylated intermediates (J. Org Chem. 43.1959) and more recently the production of astaxanthin from zeaxanthin has also been published in a single step. using oxidizers such as sodium bromate or hydrogen peroxide with relative success although very poor yields (US 6,372,946, US 6,376,717, MX PA03009685), reported between 20% and 30%. Subsequently the synthesis of astaxanthin for use as a food coloring was reported (ES 2223270) producing as intermediates arylester or oxymethylether derivatives of the carotenoid through a controlled reaction system. Such compounds are then oxidized using salts or complexes of chromium VI, manganese or mixtures thereof in aqueous medium. Procedures similar to the previous one were described by Torres-Cardona (US 7291749) using esterified zeaxanthin to produce esterified astaxanthin, mainly using zeaxanthin diacetate as raw material in both cases.

Thus, even today the synthesis of astaxanthin from another carotenoid finds extremely limited examples, such as those mentioned above. In the case of zeaxanthin as a substrate, mainly because its hydroxyl groups are sensitive to practically any oxidant, resulting in highly degradable synthetic schemes and therefore very low yields. For this reason, The process described herein includes an additional step consisting in the protection of the hydroxyl groups of zeaxanthin first to subsequently proceed with a simultaneous step of deprotection and oxidation that under the aforementioned technique produces a high yield of astaxanthin, also including the use of a catalyst and a phase transfer agent that markedly improve the oxidation step. If the group protection step is omitted then echinaenone, adonixanthin and other carotenoids are mainly obtained.

Some important natural sources for obtaining zeaxanthin as raw material for the process described here are yellow corn, orange chili, orange juice, mango, egg yolk, some modified marigold flours.

Zeaxanthin also comprises about 90% of the carotenoids of the flowers Delonix regia (Gul ohr). Also the zeaxanthin is the carotenoid of greater presence in diverse wild berries. It has also been identified in extracts of peaches, melons and apricots.

The stereochemical correlation between capsanthin and zeaxanthin and the occurrence of both pigments in Capsicum sp. has suggested a certain biogenetic relationship between the two. Of the total pigment content, zeaxanthin contributes about 6.5%, 7.3% and 15.9% respectively in the red, orange and yellow varieties of Capsicum annuum.

In corn, xanthophylls are found mainly in the endosperm. The total content of xanthophylls is estimated to range from 11 to 30 mg / Kg. The Chinese default (Lycium chínese), a small red fruit that is used in traditional Chinese medicine to improve vision contains up to 1 g / Kg of zeaxanthin dipalmitate.

From the microbial sources of xanthophylls it has been reported that Flavobacterium sp. it produces almost exclusively zeaxanthin in a purity of 95% to 99%. The zeaxanthin produced by this bacterium is identical to that produced by Zea mays. Erwinia herbicola, a non-photosynthetic bacterium, owes its yellow coloration to polar carotenoids composed mainly of mono- and zeaxanthin diglucosides. The green alga Neospongiococcum excentricum has been shown to produce more than 0.65% xanthophylls (mass on dry basis). An overproducing mutant strain of zeaxanthin zeal generated from Dunaliella salina should be considered for commercial exploitation. Zeaxanthin is also the main constituent of the outer membrane of Synechocystis sp. PCC6714. The microalga Microcystis aeruginosa is also a producer of zeaxanthin as well as Spirulina. The marine bacterium Zeaxanthinibacter enoshimenis is from the Flavobacteriaceae family that also produces zeaxanthin and is found on the island of Enoshima in Japan. Mesoflavibacter zeaxanthinifaciens is another marine bacterium from the same family that also produces the carotenoid. The red algae Coirallina officinalis, C. elongate and Jania sp. they produce b-carotene, fucoxanthin, 9, cis-fucoxanthin, fucoxanthinol, 9, cis-fucoxanthinol, 2 epimeric mutatoxanthins in addition to zeaxanthin. The blue-green symbiotic alga Cyanophora paradoxa and Glaucocystis nostochinearum synthesize only b-carotene and zeaxanthin. Other interesting microbial sources for the production of zeaxanthin are Anacystis nidulans, Dunaliella parva, Erytrotrichia carnea, Dunaliella bardawil, Prochloron sp. and Pleurochloris commutata.

Additionally, it is important to mention that traditional synthetic zeaxanthin can be used to obtain astaxanthin and is mainly composed of trans-zeaxanthin and minor amounts of cis-zeaxanthin in addition to 12'-apo-zaeaxanthin, diatoxanthin and parasiloxixanthin. However, it suffers from some disadvantages: it typically requires many steps of synthesis and each of them produces less than 100% performance so that the overall performance is quite poor. Furthermore, the synthesis produces the S-S and R-S stereoisomers of zeaxanthin and various certainly undesirable byproducts such as oxidized zeaxanthin and zeaxanthin molecules that have lost one or more of the double bonds in the polyene chain or some of the rings.

There is also the synthetically prepared zeaxanthin and the semi-synthetic zeaxanthin obtained from the isomerization of lutein, mainly the lutein contained in the marigold extracts. In general, lutein is heated for a long time in the presence of a strong base, although isomerization does not proceed 100% Due to the elimination of water under strongly basic conditions, anhydrous by-products are formed (Puré Appl. Chem., 74.1369).

Lutein from natural sources is usually accompanied by (3R, 3'R) -zeaxanthin and always retains chirality (3R, 3'R, 6'R) and zeaxanthin obtained from lutein necessarily has chirality (3R, 3'S ), this is a disadvantage of beta-epsilon arrangement (US 6420614), although it can be used for the preparation of astaxanthin.

Summary of the Invention The present invention describes the use of silylated ethers as protectants of functional groups for zeaxanthin such as -0-Si (CH3) 3, -O-Si (CH2-CH3) 3) -0-Si (isopropyl) 3, -0 -Si (CH2CH3) 2 (isopropyl), -0-Si (CH3) 2 (tert-butyl), -0-Si (CH3) 2 (n-hexyl), etc. Protective groups can be converted back into groups hydroxyl by hydrolysis. Such protection is necessary to avoid extensive oxidation of the hydroxyl groups. Subsequently the silylated derivatives are subjected to a deprotection and oxidation process which in a single-step process produces astaxanthin in high yield, only if an oxidation catalyst and a phase transfer agent are used.

Some of the preferred oxidizing systems are iodobenzoic acid, nickel peroxide, Jones reagent, Collins reagent, pyridinium chlorochromate (PCC), bipyridinium chlorochromate, trimethylsilicon chlorochromate, benzyltrimethylammonium chlorochromate, pyridinium fluorocromate, pyridinium dichromate, chromic acid, HOBr, HOC1, N-bromosuccinimide, hypochlorites such as tert-butyl hypochlorite, sodium or calcium hypochlorite, tetrabutylammonium hypochlorite, N-chlorosuccinimide, chlorates, perchlorates, bromates, iodates and periodates, dioxide of manganese, potassium permanganate, 2,3-dichloro-5,6-dicyanoquinone, p-chloranil, silver oxide, silver carbonate, silver tetraacetate, aluminum isopropoxide, perbenzoic acid and its halogenated derivatives, etc., in the presence of the catalyst and agent of Preferred phase transfer. The trimethylsiloxylated groups (TMS-O), triethyl-, tert-butyldiphenyl-, tert-butyldimethylsiloxide and commercially equivalent mixtures have been preferred to protect the hydroxyls in zeaxanthin.

The process is carried out under very mild reaction conditions with temperatures ranging from -30 ° C to room temperature and in the presence of a halogenated catalyst such as iodine and bromine salts, as well as selenium dioxide, pentoxide Vanadium and osmium tetraoxide, cerium and ammonium nitrate, ceric sulfate, ruthenium tetroxide, ruthenium trichloride or mixtures thereof are suitable.

It is a primary objective of this invention to provide a process for obtaining astaxanthin in yields of 70% or greater from zeaxanthin so that it is possible to have an economically more accessible product of the same quality as those now circulating in the market. world. The astaxanthin thus prepared is useful in aquaculture, poultry farming and as a nutraceutical for human consumption; mainly in the pigmentation of salmonids, crustaceans and other aquatic species.

It is also an object of this invention to provide a process for the preparation of oxycarotenoids such as adonixanthin, beta-cryptoxanthin, and canthaxanthin when isozeaxanthin is used as a raw material.

Scheme 1 shows the transformation of zeaxanthin into astaxanthin when the hydroxyl groups of zeaxanthin have been protected.

Zeaxanttin M¾Si-CI Pyridine 1 W10 ° C Zeaxanthin trirnethytoilylel er Scheme†. Oxidation of Sitivated Derivatives of the Zeaxantirfa Description of the invention The zeaxanthin used can be 100% pure or in the form of products containing more than 400 g of the carotenoid per kilogram of concentrate. Normally these concentrates come from natural sources so often the pigment comes in a fat matrix that does not interfere with the overall process.

In a first step, the zeaxanthin is dissolved in a solvent which can preferably be pyridine although halogenated solvents such as methylene chloride, carbon tetrachloride and chloroform are also suitable.

Once dissolved, the carotenoid is reacted with trimethylchlorosilane or any commercial silylating mixture at room temperature. Once the reaction is finished, the mixture containing the trimethylsilylether of zeaxanthin will be maintained under the same initial conditions to continue with the deprotection and oxidation process.

A minimum amount of the catalyst which can be metallic iodine is added to the above-described reaction mixture and then the pyridinium chlorochromate which is the preferred oxidant is added.

The progress of the reaction is monitored by TLC and once it has concluded with the total disappearance of the trimethylsilylether of zeaxanthin, the organic phase is decanted and the solvent is recovered by evaporation under vacuum.

The solid residue containing astaxanthin is redissolved in ethanol and is evaporated with the dual objective of eliminating other volatile residues and leading to The cis-trans thermal isomerization of the carotenoid is carried out in order to minimize the cis- isomers while the alcohol is recovered. In this way a constant proportion between the various geometrical isomers of astaxanthin is also ensured.

The zeaxanthin is dissolved in the solvent in a proportion of one part of carotenoid per 100 parts of solvent by weight although it is preferred to use 50 parts of solvent for each part of the xanthophyll.

The mixture of the pigment with the solvent is stirred vigorously in a sealed reactor so that the interior environment can be controlled, either under atmospheric conditions or in the absence of oxygen. The temperature of the process is maintained between -30 ° C and ambient temperature or between -15 ° C and 15 ° C, although it is preferred to carry it out between 0 ° C and 10 ° C, both in its group protection phase and in the oxidation.

The catalyst is used in amounts ranging from 0.1 to 2% of the weight of the pigment although it is preferred to use 0.5 to 1.0% previously dissolved in a portion of the solvent.

In the case of the oxidant, up to 10 parts of this have been used for each part of zeaxanthin, although it has been preferred to use between 3 and 5 parts of oxidant for each part of the carotenoid.

Both the group protection stage and the oxidation are carried out between 15 min and 5 h of reaction although under preferred conditions it is possible to carry out it between 1 and 3 hours. The protective agent or silylating agent is used in an amount of 10 equivalents for each equivalent of zeaxanthin although preferably 3 to 6 equivalents are used.

Below are several examples in order to illustrate the process described without this means limiting the scope of it: Example 1. 18 g of zeaxanthin were dispersed in 750 ml of chloroform and 1 g of tetrabutylammonium bromide was then added, then a solution prepared with 13 g of sodium bromate and 0.5 g of ruthenium trichloride in 250 ml of deionized water was added, adjusting its pH to 2.5. The mixture was stirred at 20 ° C and the reaction ended 120 min later. The dark red reaction mixture was first treated with a saturated solution of sodium carbonate and then with another of 20% sodium sulfite.

After standing the organic phase was decanted and washed twice, the first with a 2% sodium bicarbonate solution and the second with deionized water. 100 mg of alpha-tocopherol, 50 mg of BHT and 100 ml of soybean oil are added to the organic phase, then proceeds to evaporate to recover the solvent obtaining an oily suspension of astaxanthin containing about 50 g of astaxanthin per kilogram of suspension.

The suspension is homogenized using an Ultra Turrax homogenizer (IKA T-25) obtaining suspended crystals with a particle size distribution ranging from 0.2 to 2 microns, excellent to be formulated in diets for salmonids and crustaceans.

Example 2 In a one liter glass reactor equipped with mechanical stirring, 500 ml of pyridine are charged at room temperature and 10 g of zeaxanthin are subsequently added. The mixture is stirred vigorously until complete homogeneity. The temperature of the mixture is adjusted to 20 ° C and then 15 ml of dimethyl ferybutylsilyl chloride are added. After 5 hours of reaction, 250 mg of metallic iodine dissolved in pyridine are added and stirring is continued. Slowly add 8 g of pyridinium chlorochromate and continue the reaction for a further 2 hours. Once zeaxanthin is no longer detected by TLC, the reaction is terminated and the organic phase is decanted. The solid residue is washed with an additional 50 ml of pyridine and the washing is combined with the decantate, discarding the residual solid.

The organic phase is evaporated to recover the solvent and then 100 ml of ethanol are added to the residue even with less than 10% pyridine and the evaporation is continued until almost dry. Then the residue is washed with 300 ml of water at 40 ° C acidified with acetic acid to have a pH of 4.5 discarding the wash. An additional wash is carried out and again the washing is discarded. The solid obtained contains about 6.1 g of astaxanthin and is then mixed with 200 ml of red palm olein formulated with 150 mg of BHT, the suspension is milled (IKA colloid mil, MK 2000) until obtaining a glass size distribution of 0.2 to 2 microns. Additionally the suspension is homogenized in an Ultra Turrax homogenizer (Ultra Turrax IKA T-25) Example 3 The product obtained from the isomerization of lutein is purified using our patented methods (US 7,150,890) until it has a concentrate with 600 g of total carotenoids of which 98% is zeaxanthin.

The material thus obtained is subjected to the process described in Example 1 obtaining in the end 7.3 g of astaxanthin which represents a yield of about 66% based on the initial total carotenoids. In addition, lower amounts of adonixanthin and β-cryptoxanthin are obtained.

Example 4 In 1.0 liter of methylene chloride, 5.8 g of synthetic zeaxanthin are dissolved at room temperature and 25 ml of trimethylchlorosilane are subsequently added. After 2 h of reaction 50 mg of iodine dissolved in the same solvent were added and vigorous stirring was continued.

In 100 ml of water, 4 g of pyridinium dichromate are dissolved and added to the previous mixture. Then a 5% solution of acetic acid is slowly added until complete disappearance of zeaxanthin, which is monitored by TLC.

After the reaction is complete, the organic phase is separated and washed with 200 ml of an aqueous solution of 10% sodium thiosulfate first and then with only 200 ml of water. The solvent is recovered and the residue redissolved in ethanol and subjected to thermal isomerization while the alcohol is recovered. The final residue It contains about 4.1 g of astaxanthin which represents about 70% yield.

Example 5 In 1.0 liter of chloroform, 15 g of a purified concentrate of yellow corn xanthophylls containing 700 g of carotenoids / kilogram are dissolved of concentrate of which 95% is zeaxanthin. The temperature of the mixture is adjusted to 0 ° C and then 50 ml of ferf-butyldiphenylsilyl chloride are added. The group protection reaction is continued for 5 h and then 100 mg of metallic iodine dissolved in chloroform are added while continuing to stir. Then 25 g of bipyridinium chlorochromate is added so that the same reaction temperature is maintained and until complete disappearance of zeaxanthin. The reactor has been maintained throughout the process in an inert atmosphere.

Then the aqueous phase is discarded and the organic phase is treated with 200 ml of an aqueous 15% sodium thiosulfate solution to carry out a first wash, after discarding the washing, one more is carried out with 200 ml of an aqueous solution of bicarbonate of sodium at 2% proceeding then to discard the wash to finally make one more in the same conditions but only with water. All the washes are carried out at room temperature.

The solvent is recovered and the residue subjected to the thermal isomerization described in previous examples to finally obtain 7 g of astaxanthin corresponding to approximately 70% yield.

Example 6 500 ml of pyridine and then 10 g of isozeaxanthin are charged in a 1 liter glass reactor equipped with mechanical stirring. The mixture is stirred vigorously until complete homogeneity and then 250 mg of metallic iodine in pyridine are added. While stirring, 20 g of pyridinium chlorochromate are slowly added and the reaction is continued for a further 2 hours. Once the zeaxanthin is no longer detected by TLC, the reaction is terminated and the organic phase is decanted. The solid residue is washed with 50 ml of additional pyridine and this washing is combined with the organic phase obtained above. After recovering the solvent, 100 ml of ethanol are added and the evaporation process is continued. The residue obtained is washed a couple of times with water at 40 ° C and the washings are discarded. The solid obtained contains about 6.1 g of canthaxanthin.

Example 7 In a 2 liter glass reactor, 800 milliliters of dichloromethane are charged at room temperature with mechanical stirring and then 20 g of zeaxanthin are added. The mixture is stirred vigorously until complete dispersion, then 50 mg of osmium tetraoxide dissolved in the same solvent is added, while continuing to stir. In another vessel, 14.5 g of potassium bromate are dissolved in 300 ml of water and then added to the reactor while the reaction temperature is adjusted to 10 ° C. The phase transfer agent of cetyltrimethylammonium bromide has been used to improve the contact of the hydrophilic oxidant with the lipophilic carotenoid dissolved in the methylene chloride. Using a syringe is dosed a solution of 25% sulfuric acid to the reaction mixture until zeaxanthin is no longer detected by TLC. The reddish reaction mixture is then treated with a saturated solution of sodium carbonate first and then with a 20% sodium sulfite solution.

The reaction is terminated and the organic phase is decanted. The solid residue obtained is washed with an additional 50 ml of dichloromethane and the washing is combined with the organic phase, discarding the residual solid.

Finally, the organic phase is evaporated to recover the solvent, then adding 100 m of ethanol to the semi-solid residue when about 90% of the halogenated solvent has evaporated, then continuing to evaporate to dryness. Subsequently the residue is washed with 300 ml of water at 40 ° C, discarding the wash. This washing is repeated and the solid obtained contains about 12 g of astaxanthin.

Claims (24)

Claims:

1. A method for the preparation of astaxanthin from zeaxanthin in which a protector of the hydroxyl groups of zeaxanthin is used and subsequently an oxidizing agent is added, adding in addition a catalyst and a phase transfer agent, which acts simultaneously by deprotecting it and oxidizing it to obtain astaxanthin.

2. A method according to claim 1 in which the zeaxanthin can be of synthetic, natural or semi-synthetic origin.

3. A method according to claim 1 in which the group protectants for the hydroxyls of zeaxanthin are silylated ethers.

4. A method according to claim 2 in which the group protectants are silylated derivatives such as triethyldiphenylsiloxide, tert-butyldiphenylsyloxide, tert-butyldimethylsiloxide, trimethylsiloxide, the like or mixtures thereof.

5. A method according to claim 1 wherein the oxidizing agent can be selected from iodobenzoic acid, nickel peroxide, Jones reagent, Collins reagent, pyridinium chlorochromate (PCC), bipyridinium chlorochromate, trimethyl silicon chlorochromate, benzyltrimethylammonium chlorochromate, pyridinium fluorocromate, pyridinium dichromate, chromic acid, HOBr, HOCI, N-bromosuccinimide, hypochlorites such as tert-butyl hypochlorite, sodium or calcium hypochlorite, tetrabutylammonium hypochlorite, N-chlorosuccinimide, chlorates, perchlorates, bromates, iodates and periodates, manganese dioxide, potassium permanganate, 2,3-dichloro-5,6-dicyanoquinone, p-chloranil, silver oxide, silver carbonate, silver tetraacetate, aluminum isopropoxide, perbenzoic acid and its halogenated derivatives, similar or mixtures thereof.

6. A method according to claim 1 wherein the catalyst used can be iodo or bromine salts, ferric chloride, selenium dioxide, vanadium pentoxide, osmium tetroxide, cerium ammonium nitrate, ceric sulfate, tetroxide of ruthenium, ruthenium trichloride, similar or mixture of them.

7. A method according to claim 1 in which the mass transfer agent can be a quaternary ammonium salt such as cetyltrimethylammonium bromide and the like, quaternary phosphonium salts, sulfonium salts, the like or mixtures thereof.

8. A method according to claim 1 in which the organic solvent is pyridine, although halogenated hydrocarbons such as methylene chloride and chloroform can be used.

9. A method according to claims 1 and 6 wherein a co-solvent such as acetic acid, water, acetonitrile, benzene and its halogenated derivatives or mixtures thereof can be used.

10. A method according to claims 1, 2 and 3 in which the silylating agent is used in a proportion of 10 equivalents for each equivalent of zeaxanthin, preferably between 4 and 6 equivalents for each of zeaxanthin.

11. A method according to claims 1 and 4 wherein the oxidizing agent is used in proportion of 10 parts for each part of the substrate containing the zeaxanthin, although preferably 3 to 5 parts are used for each of zeaxanthin.

12. A method according to claim 1 in which the reaction temperature for the protection of the hydroxyl groups of zeaxanthin is between -30 ° C and 30 ° C, although it can be carried out between -15 ° C and 15 ° C C and preferably between 0 ° C and 10 ° C.

13. A method according to claims 1 and 12 in which the reaction time is between 15 min and 24 h, although it may end between 8 and 18 and preferably between 2 and 5 h.

14. A method according to claim 1 in which the reaction temperature for the deprotection and oxidation of zeaxanthin is between -30 ° C and 30 ° C, although it can be carried out between -15 ° C and 15 ° C and preferably between 0 ° C and 10 ° C.

15. A method according to claims 1, 12, 13 and 14 in which the deprotection and oxidation time is between 15 min and 24 h, although it may end between 8 and 18 h and preferably between 2 and 5 h.

16. A method according to claim 1 in which the obtained astaxanthin is subjected to a thermal isomerization process in the presence of a polar solvent.

17. A method according to claim 1 in which canthaxanthin is obtained when isozeaxanthin is used.

18. A method according to claim 1 and 16 in which the temperature of the isomerization can be between 40 ° C and 70 ° C.

19. A method according to claims 1 and 16 wherein the polar solvent may be a C2-C5 alcohol or a ketone, preferably acetone.

20. A method according to claim 1 which can be carried out under atmospheric conditions or in inert atmospheres.

21. A method according to claim 1 in which the obtained astaxanthin can be used for the pigmentation of salmonids, crustaceans and birds.

22. A method according to claim 1 in which the obtained astaxanthin can be used as an antioxidant and immunostimulant in salmonids, crustaceans and poultry.

23. A method according to claim 1 in which the obtained astaxanthin can be used as a nutraceutical for human consumption.

24. A method according to claim 1 in which the obtained astaxanthin can be used to formulate pet food for companionship.