AstaFactor Technical Report: Astaxanthin In Nature

AstaFactor^® Technical Report

Astaxanthin In Nature

Astaxanthin is the main carotenoid pigment found in aquatic animals.

Studies suggest that it can be 10 times more powerful than other carotenoids and more than 100 times than vitamin E, as a biological antioxidant.

It plays a role in many essential metabolic functions in animals: protection against oxidation and UV light, vision, immune response, pigmentation and communication, reproduction and development.

In some species it has been attributed to have vitamin-like properties and is believed to be essential to normal growth and survival.

The micro-alga Haematococcus pluvialis holds nature’s record of astaxanthin concentration, at more than 3% of dry biomass.

The main astaxanthin isomer found in Haematococcus is the same as the one found in salmon. The main form of astaxanthin in Haematococcus is the esterified form, also found in several aquatic species. It is the more stable natural form.

What is Astaxanthin?

Astaxanthin is the main carotenoid pigment found in aquatic animals.¹ This red-orange pigment is closely related to other well-known carotenoids (Fig. 1) such as beta-carotene or lutein, but has stronger antioxidant activity (10 times higher than beta-carotene)¹. Studies suggest that astaxanthin can be more than 100 times more effective as antioxidant than vitamin E.⁷

In many of the aquatic animals in which it is found, astaxanthin has a number of essential biological functions, ranging from protection against oxidation of essential polyunsaturated fatty acids, protection against UV light effects, pro-vitamin A activity, immune response, pigmentation, and communication, to reproductive behaviour and improved reproduction.² In species such as salmon or shrimp, astaxanthin is considered essential to normal growth and survival, and has been attributed vitamin-like properties.²

Some of these unique properties have also been found to be effective in mammals^3-7 and open very promising possibilities for nutraceutical and pharmaceutical applications of astaxanthin in humans.

Fig. 1. Structure of selected carotenoids

Where Is Astaxanthin Found in Nature?

Astaxanthin can be found in many of our favorite seafoods such as salmon, trout, red seabream, shrimp, lobster and fish eggs.² It is also found in a number of bird species.^8,9 Astaxanthin cannot be synthesised by animals and must be provided in the diet, as is the case with other carotenoids. While fish such as salmon are unable to convert other dietary carotenoids into astaxanthin,² some species such as shrimp have a limited capacity to convert closely related dietary carotenoids into astaxanthin, although they benefit strongly from being fed astaxanthin directly.¹⁰ Mammals lack the ability to synthesise astaxanthin, or to convert dietary astaxanthin into vitamin A: unlike beta-carotene, astaxanthin has no pro-vitamin A activity in mammals.²⁴

Some micro-organisms can be quite rich in astaxanthin. A ubiquitous micro-alga, Haematococcus pluvialis, is believed to be the organism which can accumulate the highest levels of astaxanthin in nature. The function of astaxanthin appears to be to protect the algae from adverse environment changes, such as increased UV-light photoxidation and evaporation of the water pools in which it lives.^11-13

Haematococcus algae can accumulate as much as 30 g of astaxanthin per kg of dry biomass, a level that is 1,000 to 3,000 fold higher than that found in salmon fillets. Some Haematococcus strains have even been observed to accumulate as much as 70 to 80 g of astaxanthin per kg of dry biomass.

What Forms of Astaxanthin are Found in Nature?

Form and level of deposition of astaxanthin differ between tissues and species (cf. Tables 1 & 2). In salmon, esterified astaxanthin predominates in the skin, teguments, and eggs, while free astaxanthin is the main form in the flesh, serum and other internal organs.² In shrimp, esterified astaxanthin predominates, except in the ovaries and eggs.^17,18 In red seabream, mostly esterified astaxanthin is found in the skin.^14,15 The more stable esterified form is believed to be an adaptive feature to be able to store astaxanthin in tissues without excessive oxidation.¹ Esterified astaxanthin is the main form found in Haematococcus pluvialis.

Although they have the same chemical composition, 3 of the astaxanthin molecule can be found in nature. They are the 3S,3'S, 3R,3'S, and 3R,3'R stereoisomers, characterized by the configuration of the two hydroxyl groups on the molecule (cf. Fig. 2). A recent study by the FDA concluded that the 3S,3'S is the main stereoisomer found in wild Pacific and Atlantic salmon species and that in order to achieve the same astaxanthin stereoisomer profile as their wild counterparts, farmed salmon should be fed a diet containing the same astaxanthin stereoisomers as in the natural diet of wild salmon.¹⁶

The 3S,3'S stereoisomer is the main form found in Haematococcus pluvialis, while synthetic astaxanthin contains primarily the 3R,3'S stereoisomer. Salmon appear unable to convert the 3R,3’S stereoisomer into the more common 3S,3'S form. In fact, the FDA study clearly showed that farmed salmon could be easily distinguished from the wild salmon because the farmed salmon are fed synthetic astaxanthin and accumulate astaxanthin isomers in the flesh in the same ratio as is found in their diet. This suggests that consumers may prefer to eat farmed salmon fed a natural form of astaxanthin.

Table 1. Main forms of astaxanthin in tissues of important aquaculture species

Tissues

Skin

Flesh

Digestive
gland

Ovaries

Serum

Eggs

Species

Salmonids²

Shrimp^17,18

Red Seabream^14,15

Esterified

Free

Esterified

N.D.

Free

N.D.

Free

N.D.

Free

N.A.

N.D.

Esterified

Free

N.D.

N.D.: not determined

Fig. 2. Astaxanthin enantiomers

Table 2. Form and level of astaxanthin in selected important aquaculture species and potential astaxanthin sources

Aquaculture species	Content (mg/kg)	Astaxanthin Free/esterified	Main isomer	Ref.
Sockeye salmon	26-37	Free,esterified*	3S,3'S	^2,16
Coho salmon	9-21	Free,esterified**	3S,3'S	^2,16
Chum salmon	3-8	Free,esterified**	3S,3'S	^2,16
Chinook salmon	8-9	Free,esterified**	3S,3'S	^2,16
Pink salmon	4-6	Free,esterified**	3S,3'S	^2,16
Atlantic salmon	3-11	Free,esterified**	3S,3'S	^2,16
Rainbow trout	1-3	Free,esterified**	3S,3'S	²
Salmon eggs	0-14	Esterified***	N.A.	^19,20
Red seabream	2-14	Esterified***	N.A.	^14,15
Red seabream eggs	3-8	N.A.	N.A.	²⁰
Black tiger prawn	10-150	Esterified,free**	3S,3'S	¹⁸
Lobster		Esterified,free**	N.A.*	^21,22
Astaxanthin sources
Copepods	39-84	Esterified***	N.A.*	²
Krill	46-130	Esterified***	3R,3'R	²
Krill oil	727	Esterified***	3R,3'R	²
Crayfish meal	137	Esterified***	N.A.*	²
Arctic shrimp	1160	Esterified***	3S,3'S	²
Yeast	30-800	Esterified***	3R,3'R	²
Synthetic astaxanthin	80,000	Free	3R,3'S	²
Haematococcus pluvialis	10,000 to 30,000	Esterified***	3S,3'S	23
Crustaceans are believed to have mostly the 3S,-3'S form, Krill might be the exception. * Depending on tissues, free or esterified astaxanthin may be found *** Also contain a small proportion of free astaxanthin N.A.: not available

References

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