Progress in the study of functional properties of astaxanthin and its application in functional foods

Astaxanthin (Astaxanthin), also known as astaxanthin, astaxanthin, shrimp and crab shells, oysters, salmon and some algae contain carotenoid oxygen derivatives, can effectively quench reactive oxygen species, has a high nutritional and health value.

As early as the thirties of the twentieth century, researchers from the shell of shrimp and crab isolated astaxanthin, but its physiological function until the eighties of the twentieth century has attracted widespread attention to the animal and clinical experimental studies have shown that astaxanthin has a strong antioxidant, anti-cancer and cancer inhibition, enhancement of immunity, the prevention of cardiovascular disease and other health care functions, with a broad application prospects.

Physical and chemical properties of astaxanthin

Crystalline astaxanthin is pink, melting point of 215 ℃ ~ 216 ℃, insoluble in water, with fat soluble, soluble in chloroform, acetone, benzene and other organic solvents. Astaxanthin molecular structure of the conjugated double bond chain and its end of the unsaturated ketone group and hydroxyl, has a more active electronic effect, can attract free radicals unpaired electrons or to provide electrons to the free radicals, so as to scavenge the free radicals, has a strong antioxidant effect.

The structure also makes it easy to interact with light, heat, oxides, structural changes in the degradation of astaxanthin. It was found that visible light on astaxanthin has a small impact, and ultraviolet light on astaxanthin has a great destructive effect; 70 ℃ below, the temperature of astaxanthin has a small impact, 70 ℃ or more, astaxanthin began to be destroyed by the heat; in the range of pH4 ~ 11, pH on astaxanthin has a very small impact, pH <3 or pH> 13 astaxanthin began to be degraded; Ca2 ＋, Mg2 ＋, K ＋, Na ＋, Zn2 + and other metal ions on astaxanthin basically has no effect, Fe2 +, Fe3 +, Cu2 + on astaxanthin has a significant destructive effect, of which Fe3 + has the greatest impact.

Astaxanthin mainly free state and esterified form. Free astaxanthin is extremely unstable, easy to be oxidised, usually chemically synthesized astaxanthin for the free form. Esterified astaxanthin is due to astaxanthin terminal ring structure each has a hydroxyl group is easy to form esters with fatty acids and stable, aquatic animal skin and shell astaxanthin, red algae, red yeast astaxanthin are mainly in the esterified state is mainly esterified state according to its combination of fatty acids are divided into astaxanthin monoester and astaxanthin diester. When astaxanthin is esterified, its hydrophobicity is enhanced, and the diester is more lipophilic than the monoester; at the same time, astaxanthin in the esterified state will form complexes with proteins to produce different colours.

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Functional properties of astaxanthin

In recent years, with the important physiological functions and great economic value of astaxanthin gradually known, the domestic and foreign research on the functional properties of astaxanthin is increasing, especially in the antioxidant, anticancer and cancer inhibition, enhancement of immunity, anti-hypertension, prevention of cardiovascular disease, anti-ultraviolet radiation and so on.

2.1 Antioxidant
Astaxanthin is a chain-breaking antioxidant with extremely strong antioxidant effects. The organism can produce a small amount of oxygen free radicals during normal life activities such as electron transfer in the respiratory chain and oxidation of other substances in the body, and a large number of oxygen free radicals will be produced when stimulated by chemical reagents and ultraviolet radiation.

These free radicals can cause lipid peroxidation, amino acid oxidation, protein degradation and DNA damage on biological membranes, but also make the unsaturated fatty acids on the cell membrane chain reaction, thus affecting the composition of cells. Astaxanthin can not only quench single-linear oxygen, direct scavenging of oxygen radicals, but also block the chain reaction of fatty acids.

It was found that the ability of multiple carotenoids to quench molecular oxygen is in the following order: astaxanthin > α-carotene > β-carotene > rhododendron > zeaxanthin > lutein > bilirubin > bilirubin, Lee et al. found that the role of five carotenoids and their derivatives, namely lutein, zeaxanthin, lycopene, isozeaxanthin, and astaxanthin, which have different numbers of conjugated bonds, in the photo-oxidation of soya bean oil, in quenching reactive oxygen species, and found that quenching reactive oxygen species is a very important factor for the development of the soya bean oil. It was found that the ability to quench reactive oxygen species increased with the increase of conjugated double bonds, and astaxanthin had the strongest quenching performance.

Some researchers have also applied the thiobarbituric acid method to test the ED50 (see Table 1) for the half-effect dose of free radical scavenging of carotenoids and their derivatives and α-tocopherol (VE) for each subject, using heme proteins containing ferrous ions as the free radical generators and linoleic acid as the acceptor, and similarly found that astaxanthin has the strongest radical scavenging ability.

In recent years, there is also continuous research to prove that astaxanthin’s antioxidant effect is more than 100 times stronger than that of α-tocopherol, and it is known as “super VE”. At the same time, astaxanthin can effectively prevent the peroxidation of phospholipids and other lipids. In addition, astaxanthin can also increase the activity of antioxidant enzymes and protein expression, different doses of astaxanthin in animal cells peroxiredoxin and superoxide dismutase protein expression have increased significantly, and its biological activity has also been significantly improved.

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2.2 Anti-cancer
The relationship between dietary carotenoid intake and cancer incidence or mortality was found to be significantly negatively correlated with carotenoid intake [14].Nishino [15] compared the anticarcinogenic activity of various carotenoids and concluded that astaxanthin had the strongest anticarcinogenic effect.

Savoure et al. demonstrated that the tumourigenic effect of astaxanthin lies in the inhibition of tumour proliferation. Currently, studies have shown that Cell Gap Junction Communication plays an important role in regulating the normal proliferation and differentiation of cells and the stability of tissues, and that the inhibition or destruction of its function is an important mechanism in the stage of pro-carcinogenesis.

The anticancer effect of astaxanthin is closely related to its ability to induce Cell Gap Junction Communication, which can isolate cancer cells and reduce the connection between cancer cells by strengthening the connectivity between normal cells in order to control their growth and prevent tumour transformation.

A large number of studies at home and abroad have further shown that astaxanthin has a significant inhibitory or preventive effect on a variety of cancers, such as Tanaka et al. observed through animal experiments that astaxanthin has a preventive effect on oral cancer and bladder cancer; Gradelet et al. showed that astaxanthin has a significant effect on inhibiting hepatocellular carcinoma; it has also been shown that astaxanthin prevents the growth and transformation of human fibroblasts (1BR-3), melanocytes (HEMAc) and intestinal tumours. (HEMAc) and intestinal CaCo-2 cells from DNA damage caused by ultraviolet radiation, thereby reducing the occurrence of skin cancer.

2.3 Enhancement of immunity
In a study by Jyonouchi et al. on the immunomodulatory effects of astaxanthin and carotenoids on mouse lymphocytes in an in vitro tissue culture system, astaxanthin was found to have a strong immunomodulatory effect. It was shown that astaxanthin significantly promotes the production of antibodies in mouse splenocytes in response to thymus-dependent antigen (TD-Ag) and improves the conclusion of humoral immune responses dependent on T-specific antigens.

Also, both astaxanthin and carotenoids were found to significantly promote antibody production in response to TD-Ag stimulation and increase the number of cells secreting IgG and IgM in an in vitro study of human blood cells, whereas supplementation with astaxanthin partially restored antibody production in response to TD-Ag in aged mice, contributing to the restoration of humoral immunity in aged animals.

The results of Chew et al.’s study on the effects of ingestion of β-carotene, astaxanthin and zebra mussel yellow on splenocyte function in mice showed that β-carotene and astaxanthin had the effect of significantly enhancing the function of splenic lymphocytes in mice in order to enhance the body’s immunity.

In addition, astaxanthin also enhances the production of human immunoglobulin as well as the ability to release interleukin-1 and tumour necrosis factor in mice, which is stronger than β-carotene and keratine. Thus, astaxanthin has a strong activity of inducing cell division and has an important immunomodulatory effect.

2.4 Antihypertensive
Hussein et al [27] investigated the antihypertensive effect of astaxanthin in spontaneously hypertensive rats (SHR), and the results showed that continuous feeding of astaxanthin for 14 d resulted in a significant reduction of arterial blood pressure in SHR; continuous feeding of astaxanthin (50 mg-kg-1) for 5 weeks in stroke-prone SHR resulted in a significant reduction of blood pressure, and also delayed the onset of stroke in SHR.

Regarding the mechanism of action of the anti-hypertensive effect of astaxanthin, some studies have shown that astaxanthin can regulate blood rheology, including the sympathoadrenergic receptor pathway, ensure the normalisation of α-adrenergic receptor sensitivity, as well as attenuate vasoconstriction induced by Ang II and reactive oxygen species as a means of repairing the vascular tension state, and achieving the anti-hypertensive effect.

Harry et al. carried out experiments using Juk fatty acid rats (ZFR) as a model, proving that astaxanthin has the ability to resist hypertension and reduce the activity of the renin-angiotensin system (RAS).

2.5 Prevention of cardiovascular diseases
Clinical studies have shown that oxidation of low-density lipoprotein (LDL) is an important cause of atherosclerosis, and the higher the concentration of LDL in the human body, coupled with platelet deposition that makes blood vessels thinner and impedes the speed of blood flow, the higher the risk of atherosclerosis in the organism [30].

Normally LDL exists in a non-oxidised state, oxidised low-density lipoprotein (ox-LDL) converts cells into foam cells and lipid streaks, and the presence of foam cells in the inflamed vessel wall leads to increased oxidative capacity, peripheral smooth muscle cell proliferation and arterial narrowing.

Epidemiological and clinical data suggest that dietary antioxidants prevent cardiovascular disease. This is an important reason why astaxanthin is effective in preventing atherosclerosis. In addition, astaxanthin reduces macrophage infiltration in arterial plaques, preventing the formation of atherosclerotic material and having a stabilising effect on plaques.

Murillo et al. through the study found that astaxanthin in the body has a significant increase in HDL, reduce the effectiveness of LDL. Therefore, astaxanthin has the role of preventing cardiovascular diseases such as atherosclerosis, coronary heart disease and ischaemic brain damage.

2.6 Anti-ultraviolet radiation
Studies have shown that the skin and other tissues exposed to bright light, especially ultraviolet light, can lead to cell membranes and tissues to produce monoatomic oxygen and free radicals, so that the body is subject to oxidative damage.

These damages can be effectively reduced when the body consumes sufficient antioxidants such as carotenoids represented by β-carotene from food. Carotenoids in nature play an important role in protecting tissues against UV oxidation.

Astaxanthin, on the other hand, has the property of preventing UV radiation damage more effectively than beta-carotene and lutein, etc. On the other hand, astaxanthin has a special effect on the enzyme glutamine transglutaminase (Transglutaminase), which is able to consume putrescine when the skin is exposed to light, in order to prevent the accumulation of putrescine.

In Japan, astaxanthin was tested for skin protection, and the results showed that astaxanthin had a significant improvement in skin tension, moisture content, tone, elasticity and smoothness. Therefore, astaxanthin can be used as a potential UV radiation protection agent, for the protection of cell membranes and mitochondrial membranes from oxidative damage, to prevent skin photoaging, and maintain skin health plays an important role.

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Application in functional food

A large number of studies at home and abroad have shown that astaxanthin can effectively remove free radicals generated by exercise in muscle cells, strengthen the oxygen-demanding metabolism, with significant anti-fatigue and slow aging effect; can significantly improve human immunity; is the only carotenoid that can pass the blood-brain barrier, with the advantage of antioxidant protection of the eyes, with a variety of important and unique health care function characteristics. It can also be used in the capacity of new functional food additives as food colouring agents, antioxidants, etc., to enhance the quality of food and the perception of food.

3.1 Application in anti-aging functional foods
Organism aging is mainly caused by a large number of free radicals generated in the chain oxidation reaction in the mitochondria, if not cleared in time will lead to mitochondrial oxidative damage, accelerating the aging of organism cells. Astaxanthin has a strong antioxidant activity, can be efficiently scavenging oxygen free radicals, its efficiency is more than 100 times that of VE.

Astaxanthin not only maintains a strong antioxidant capacity, but also slows down age-related functional decline and helps resist aging. Therefore, adding astaxanthin into functional foods will help prevent a series of diseases caused by organ aging and improve people’s health.

At present, foreign countries have carried out astaxanthin anti-aging functional food research and development, such as the United States Cyanotech company launched Derma Astin (Derma) natural astaxanthin capsules.

In addition, astaxanthin and beauty factor combination with the production of anti-aging beauty food, and cosmetics with the use, enhance its anti-aging effect. According to the survey, 90% of the international first-line cosmetic brands have launched a beauty food containing astaxanthin, such as Shiseido’s “living face G + C”.

3.2 Application in food to enhance immune function
Astaxanthin can significantly promote the ability of splenocytes to produce antibodies in the presence of antigens, and enhance the production of immunoglobulins in blood cells stimulated by T cells in the human body.

Astaxanthin also enhances the specific humoral immune response at the initial stage of antigen invasion. Astaxanthin has an optimal cytokinesis-inducing activity that enhances the production of immunoglobulins in the body, which has an important immunomodulatory role.Goswami et al. found that astaxanthin can be of great utility as an immunomodulator.

Therefore, the application of astaxanthin to enhance the body’s immune health food is an important direction for the development of astaxanthin. Japan has launched a variety of astaxanthin products, such as Fancl brand “astaxanthin 30 days” and other immune-enhancing nutritional products.

Japan Suntory company application of astaxanthin and other functional extracts with the method, the production of a variety of functional role of higher new products. Such as astaxanthin and other carotenoids group with, in order to strengthen its immunity.

3.3 In the eye protection function of food applications
The main diseases that cause visual damage and even blindness are age-related macular degeneration (AMD) and senile cataract, both of which are related to the photo-oxidation process inside the eye. The human retina contains more polyunsaturated fatty acids and high concentration of oxygen than any other tissues, and when high-energy blue light is applied to the retina, the mono-linear oxygen produced by photo-oxidation and oxygen radicals will cause peroxidative damage to the retina. Peroxidative damage.

In humans and other animals, dietary carotenoids, which are essential for eye health, quench these damaging reactive oxygen species and help the retina resist oxidative damage. Studies have shown that astaxanthin can cross the blood-brain barrier and effectively prevent retinal oxidation and photoreceptor cell damage, suggesting that astaxanthin is effective in preventing and treating “age-related macular degeneration” and improving retinal function.

Therefore, astaxanthin applied to the protection of eyesight, maintenance of eye health functional food is the current domestic and foreign research hot topics. Such as Japan will astaxanthin and blueberry extract group with, in order to strengthen the effect of vision protection; the United States has developed a natural astaxanthin capsules and other products came out, dedicated to the protection of eyesight, to improve the aging retinal macular degeneration.

3.4 Application in functional food additives
In the food industry, astaxanthin can not only be used as immune enhancers, anti-aging agents and other functional ingredients added to food, but also be able to effectively play a role in preserving freshness, colour, flavour, quality and so on, as a food colouring agent, antioxidant and so on. Used to maintain the original nutrients of food without damage to the loss or improve the sensory properties, enhance the attractiveness of food to consumers.

Astaxanthin is a fat-soluble pigment with brilliant red colour, natural and realistic, strong pigment deposition ability, strong colouring power, safe and non-toxic, low dosage, no peculiar smell and good taste. It can be used in the colouring of many health products as well as the colouring of sugar coating of tablets and capsules. It can also be directly used in foodstuffs, such as edible fats and oils, margarine, ice cream, candies, pastries, noodles, seasonings, etc. Especially the foodstuffs containing more lipids, which have both good colouring effect and remarkable preservation effect. Can also be used for beverage colouring, especially for fruit juice containing VC is most suitable.

In Japan, the use of astaxanthin as a functional food additive has been more common, the red oil containing astaxanthin is widely used in vegetables, seaweeds and fruits marinade, in the beverage, noodles, seasoning colouring and so on have also been reported.

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Conclusion and Prospect

A large number of studies at home and abroad have proved that astaxanthin has potential special health effects in the human body, making astaxanthin more and more popular. At present, the main sources of astaxanthin include chemical synthesis and natural extraction.

Chemically synthesized astaxanthin and natural astaxanthin in the structure, nature, application and safety are some differences, its stability, antioxidant, colouring and other important properties are significantly lower than the natural astaxanthin, natural astaxanthin efficient extraction and preparation of astaxanthin is the focus of the development of astaxanthin in the future, in particular, the use of yeast, algae and other microorganisms industrial fermentation production of astaxanthin, the production cycle is short, promising.

Therefore, screening high-yielding strains, improving the fermentation process, introducing gene improvement technology at the right time, increasing the yield and reducing the cost will greatly help the further development and application of astaxanthin.

Astaxanthin in the field of functional food applications, foreign countries are mainly located in its efficacy to strengthen the immune, anti-cancer, anti-aging, retinal protection, anti-inflammatory, prevention of oxidative damage to blood low-density lipoprotein cholesterol (LDL-C), research and development of the production of a number of health care nutritional food containing astaxanthin, dietary supplements and so on.

And China is still in the primary stage. With the in-depth study of the functional properties of astaxanthin, production technology to improve the perfect, while combining our traditional “medicine and food” concept, the use of astaxanthin development of functional nutritional food, will have excellent prospects for the application of far-reaching development significance.