What Are the Uses of Astaxanthin for Skin Care?

In 933, R. Kuhn and others [1] extracted a purplish red crystal from shrimp and crab, which they named ovester. However, it was later discovered in 1938 that it was not an ester, but a new carotenoid closely related to astaxanthin. It was then named astaxanthin and its chemical structure was determined. Astaxanthin is a red pigment that is widely found in living organisms. Although the term “astaxanthin” is not commonly used in daily life, astaxanthin is found in many kinds of human food. The red color of most crustaceans such as shrimp, lobster, and crab is due to the accumulation of astaxanthin. The flesh color of some fish such as salmon is also the result of astaxanthin accumulation. Astaxanthin is a carotenoid with a wide range of applications. Due to its special coloring and physiological functions, it has attracted the attention of researchers and industries in the chemical, food and cosmetic industries at home and abroad in recent years.

1 Sources of astaxanthin

The sources of astaxanthin are mainly divided into chemical synthesis and natural extraction.

1.1 Chemical synthesis

Astaxanthin is the end product of carotenoid synthesis. It is difficult to synthesize artificially, and most of it has a cis-structure. The US FDA only approves astaxanthin with a trans-structure for industrial production. So far, the only company that synthesizes astaxanthin using chemical synthesis is Roche in Switzerland, and the astaxanthin content of its products is 5% to 10%.

1.2 Natural extraction method

1.2.1 Extraction from aquatic product processing waste

The usual method is to crush the shells of shrimp and crab, then acid-digest them, and finally extract them with an organic solvent such as acetone or petroleum ether. A polymerization agent system is used abroad to extract astaxanthin, astaxanthin esters and shrimp red pigment from the waste of crayfish. The yield is as high as 153 μg/g. According to analysis, astaxanthin accounts for more than 90% of the extracted carotenoids. However, the lime content in the waste is not conducive to the extraction of astaxanthin and should be removed as much as possible before extraction. Recently, Norway has used ensiling to treat waste, that is, adding organic or inorganic acids to break the bond between astaxanthin and the protein or skeletal parts, so that it can be freed from the bound state. After ensiling, the recovery rate of astaxanthin has increased by 10%, and the purity has also been greatly improved.

1.2.2 Extraction of astaxanthin from cultivated algae

Many algae can produce astaxanthin, and Haematococcus pluvialis [2] is a very important astaxanthin-producing algae. If there is a lack of nitrogen during the cultivation of this algae, astaxanthin will accumulate in the algae. If Fe2+ is added to the culture medium, the synthesis of astaxanthin will increase significantly, and the cell morphology will change from vegetative cells to cell sacs. Light intensity, duration and the nature of the light affect the accumulation of astaxanthin. Haematococcus pluvialis contains 0.2% to 2.0% astaxanthin, but the long cultivation cycle, the need for light and cell disruption are not conducive to large-scale production.

1.2.3 Extraction of astaxanthin from yeast

At present, red yeast is mainly used abroad as a strain for fermenting astaxanthin. Red yeast has some of the necessary characteristics for being a biological source of astaxanthin: as a major carotenoid in astaxanthin synthesis, it does not require light, can use a variety of sugars as carbon sources for rapid heterotrophic metabolism, has a short culture time, can be cultivated at high density in a fermenter, and the single cells of the bacteria after pigment extraction can be used as bait, feed additives, etc. These advantages have made Rhodotorula glutinis a focus of research. Studies have shown that the ability to synthesize astaxanthin is greatly enhanced when tomato juice is added to the culture medium. However, the astaxanthin content of the wild-type Rhodotorula glutinis is not high enough, only 200 to 300 mg/kg; therefore, current research is mainly focused on the selection of high-yield astaxanthin strains, the development of inexpensive culture media, and the optimization of culture processes.

2. Composition and characteristics of astaxanthin

Astaxanthin (3,3'-dihydroxy-beta,beta'-carotene-4,4'-dione) [3] is a keto-carotenoid with the molecular formula C40 H52 O4 and a relative molecular weight of 596.86. Pure astaxanthin is a purple needle-like crystal with a luster. It has a melting point of 216°C, is insoluble in water, soluble in chloroform and pyridine, and slightly soluble in most organic solvents such as petroleum ether and ethanol. The chemical structure of astaxanthin is composed of four isoprene units linked by conjugated double bonds, with two isoprene units at each end to form a six-membered ring structure (as shown in the figure below).

The important property of astaxanthin is its antioxidant properties [4]. Biological oxidation is the process by which organic substances such as sugars, lipids and proteins undergo a series of oxidative decomposition in the body, ultimately generating carbon dioxide and water and releasing energy. Biological oxidation is essential for life. Under normal circumstances, oxidation reactions are regulated and controlled by the body, but when free radicals are produced, peroxidation reactions occur. Free radicals are atoms or groups of atoms with unpaired electrons, such as the superoxide anion radical (O2 · ), hydroxyl radical (OH · ), hydrogen radical (H · ), and methyl radical (CH3 · ). Radicals are very active and highly reactive, and can trigger chain reactions that cause lipid peroxidation in biological membranes, thereby destroying the structure and function of the membrane. They can cause protein denaturation and cross-linking, inactivate enzymes and hormones, reduce the body's immune capacity, destroy the structure of nucleic acids, cause metabolic abnormalities, etc.[5].

Astaxanthin molecules have long conjugated double bonds, hydroxyl groups and unsaturated ketones at the ends of the conjugated double bond chains, among which the hydroxyl and ketone groups form an α-hydroxy ketone. These structures all have relatively active electronic effects, which can provide electrons to free radicals or attract the unpaired electrons of free radicals. It can be seen that the structural characteristics of astaxanthin make it extremely reactive with free radicals, which removes free radicals and has an antioxidant effect.

Studies have shown that astaxanthin has an antioxidant property that is more than 10 times higher than β-carotene. It also has a lipid peroxidation inhibition property that is more than 1000 times higher than vitamin E. It is well known that β-carotene can be hydrolyzed to obtain two vitamins A. Although astaxanthin is not a vitamin A breakdown product, it still has similar properties to vitamin A. Therefore, astaxanthin, which is characterized by its strong antioxidant properties, should also have some of the biological functions of β-carotene, vitamin E and vitamin A. In summary, astaxanthin has very strong vitamin-like properties. Some researchers have demonstrated the excellent biological functions of astaxanthin, such as inhibiting the oxidation of polyunsaturated fatty acids, protecting against ultraviolet rays, provitamin A activity, improving eyesight, immunity, pigment formation and nerve connections, and improving fertility.

3 Applications of astaxanthin

3.1 Astaxanthin in the feed industry

Astaxanthin can be used as a feed additive for abalone, sturgeon, salmon, rainbow trout, red sea bream, crustaceans and ornamental fish, as well as various poultry and pigs. [6] Its main functions are: (1) to increase nutritional and commercial value as a natural pigment. Astaxanthin added to feed accumulates in fish and crustaceans, making the adults red, bright in color, and rich in nutrients. The general content is many times higher than that of adults. After meat and poultry are fed with astaxanthin-added feed, the amount of egg yolk increases, and the skin, feet, and beaks appear golden yellow, which greatly improves the nutritional and commercial value of eggs and meat. Eating these products is beneficial to human health. (2) As a natural hormone to improve reproductive ability [7]. Astaxanthin can be used as a natural hormone to promote fertilization of fish eggs, reduce embryonic mortality, promote individual growth, increase maturation speed and reproductive power. (3) As an immune enhancer to improve health. Astaxanthin is stronger than β-carotene in terms of its ability to scavenge free radicals and eliminate free radicals. It can promote the production of antibodies and enhance the immune function of animals. (4) Improves the color of skin and muscles. Adding 50mg/kg astaxanthin to the feed of ornamental fish such as red swordtail, pearl Mary fish and flower Mary fish can effectively improve the body color of the fish and enhance its ornamental value.

3.2 Application of astaxanthin in cosmetics

Natural seaweed extract—astaxanthin is the strongest antioxidant vitamin in nature and has the reputation of being the “super vitamin E”. Its antioxidant activity is 550 times that of vitamin E, which can effectively protect the skin from ultraviolet (UVA, UVB) damage. When the skin is exposed to light, it consumes putrescine[6]. It is used as a potential photoprotectant to prevent photoaging of the skin and prevent skin cancer. Its super ability to eliminate free radicals can prevent skin cells from being damaged by free radicals, reducing the production of wrinkles and freckles. In addition to its many medicinal and additive uses, astaxanthin is currently widely used as a new cosmetic ingredient in creams, emulsions, lip balms, skin care products and other types of cosmetics due to its excellent properties.

3.2.1 Used in facial skin care creams

The structural characteristics of astaxanthin make it very reactive with free radicals and remove them [8], providing an antioxidant effect. Used in skin care products, it can prevent and delay skin aging and reduce the appearance of wrinkles and freckles. Example of a formulation used in skin care creams for whitening and anti-aging (w/%): powdered natural astaxanthin 0.2, soluble eggshell membrane 0.5, cetyl phosphate betaine 0.5, squalane 10.0, white wax 5.0, cetyl alcohol 4.0, Span 60 2.0, Tween 60 2.0, glycerin 5.0, fragrance 0.1, para 0, cetyl phosphate betaine 0. 5, squalane 10. 0, white wax 5 . 0, cetyl alcohol 4. 0, Span 60 2. 0, Tween 60 2. 0, glycerin 5. 0, flavor 0. 1, methylparaben 0. 1, deionized water to 100. This formula makes the skin moist, supple and elastic. Long-term use can reduce wrinkles, remove pigmentation and whiten, and delay skin aging.

3.2.2 Use in sunscreen cosmetics

Ultraviolet radiation is an important cause of photoaging of the epidermis and skin cancer. Astaxanthin can effectively scavenge free radicals produced in the body by ultraviolet radiation and regulate and reduce these photochemical damages. Astaxanthin also has a special effect on transglutaminase, which can consume putrescine when the skin is exposed to light, indicating that astaxanthin's strong antioxidant activity can be used as a potential photoprotective agent to prevent photoaging of the skin and prevent skin cancer. Example formula for use in sunscreen lotions to protect against UV rays (w/%): powdered natural astaxanthin 0.5, cetyl/stearyl alcohol 8, white oil 4.5, isopropyl palmitate 4.5, dimethicone 1.5, sPP-200 2.5, monoglycerides 2.5, Lanolin 1.5, Polyethylene glycol 6000 0.5, Coconut oil 4, sPP-200 2.5, Fragrance, Preservative 0.1, Deionized water to 100. It can provide long-lasting protection against ultraviolet radiation, resist oxidation, eliminate free radicals, and provide excellent protection against tanning, sunburn, and aging. It can inhibit and lighten melanin for a long time, providing long-lasting whitening effects on the skin.

3.2.3 Colorant for cosmetics

Astaxanthin can be used as a fat-soluble pigment. It has a bright red color and strong antioxidant properties. In cosmetics, it can not only effectively maintain color, flavor and shelf life, but also be used as a long-lasting colorant, such as in lipsticks and lip glosses.

3.2.4 Cosmetics for special purposes

Astaxanthin is used in cosmetics not only as an excellent antioxidant and coloring agent, but also as an auxiliary agent with outstanding therapeutic effects [9]. It has many unique uses: (1) As a common antibacterial peroxide, it has the effect of delaying aging. Astaxanthin can quench a variety of reactive oxygen species produced by strong light and excessive oxidation, prevent the damage of reactive oxygen species to cells, and its antioxidant capacity is significantly higher than other carotenoids. (2) Anti-cancer activity: Astaxanthin can inhibit the peroxidation of organisms in the body, thereby inhibiting the mutagenic process of cancer cells and playing an anti-cancer role. (3) Prevention of atherosclerosis and related diseases: Due to the antioxidant properties of astaxanthin, the oxidation of unsaturated fatty acids in the blood is inhibited, the deposits on the walls of blood vessels are reduced, and the formation of atherosclerosis is inhibited. (4) Maintaining the health of the eyes and central nervous system: The retina contains a high concentration of polyunsaturated fatty acids and a high concentration of oxygen, and the central nervous system is rich in unsaturated fatty acids and iron, all of which are extremely susceptible to oxidative damage. Astaxanthin can pass through the blood-cerebrospinal fluid barrier and quench damaging reactive oxygen species. (5) Improves immunity. Astaxanthin has the best activity in inducing cell division and an important immunomodulatory effect, and can be used as an immune enhancer.

4 Prospects

Astaxanthin, as a cosmetic ingredient with unique functions and a wide range of applications, has attracted widespread attention in the cosmetics industry at home and abroad. Cosmetics with astaxanthin as a functional ingredient have become a research topic in the international daily chemical industry, and their application prospects are very broad. The research and development of new cosmetics in China is also changing with each passing day, and the market competition is fierce. Natural and environmentally friendly cosmetic additives have become the main research direction today. Therefore, with the rapid development of science and technology and the trend of people advocating naturalness, it is necessary to make full use of domestic astaxanthin resources, research and develop new, high-end astaxanthin functional cosmetics to meet the growing needs of consumers and improve the health of the nation. The potential economic benefits and social effects are also obvious.

References

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