Astaxanthin, the antioxidant pigment superior to beta-carotene.

Belonging to the family of carotenoids, theastaxanthin is a liposoluble pigment classified within the large family of terpenes and phytochemical compounds. Its structure was first discovered by Professor Basil WEEDON in 1975. He then determined that, unlike other carotenoids, astaxanthin does not convert into vitamin A in the body. This peculiarity has paved the way for in-depth studies of this molecule. Indeed, an excess of vitamin A in the body is harmful to health.

Astaxanthin typically originates from unicellular algae with its primary natural source being the micro-algae Haematococcus pluvialis. Found in a solid form, it displays a red or orange colour. Present in certain seafood, its colour explains the orange-red colouration of crustaceans (shrimp, lobsters, crabs, lobsters...) and fish (salmon, trout...).

The potent and unique antioxidant power of astaxanthin rests on its ability to cross the cell membrane. Indeed, it possesses both lipophilic and hydrophilic properties. It can combine with the cell membrane from both the inside and the outside. Due to its chemical structure, its polar groups overlap the polar regions of the cell membrane, while the central non-polar area of the molecule inserts itself into the internal non-polar region of the membrane.

Thus, astaxanthin can take a transmembrane alignment in biological membranes, assisting in maintaining the membrane structure and reducing membrane fluidity. This property allows it to act as a cellular shield to combat free radicals, thereby protecting the entire cells of the organism.

The presence of hydroxyl (OH) and ketone (C=O) groups on each ionone grouping is the reason for its higher antioxidant activity. The oxo function is capable of stabilising carbon radicals through resonance, which may explain the powerful antioxidant properties of astaxanthin without pro-oxidant contributions. This means it can never cause destructive oxidation in the body, which is a health benefit.

Astaxanthin traps singlet oxygen, a source of oxidative stress. It captures free radicals and neutralises them, without harming somatic cells. A powerful antioxidant, the astaxanthin molecule is similar to beta-carotene. The differences lie in the chemical and biological properties.

Furthermore, a study compared the inhibitory action of astaxanthin and beta-carotene on the production of lipid peroxides, which are responsible for the formation of free radicals. The results showed that astaxanthin was twice as effective as beta-carotene. This difference is linked to their chemical structure.

The conjugated polyene fraction and terminal cyclic fractions of astaxanthin trap radicals both on the surface of the membrane and within the membrane, whereas for beta-carotene, only its polyene chain is responsible for trapping radicals near the membrane surface and within the membrane. Thus, astaxanthin has a stronger action than beta-carotene on inhibiting the formation of lipid peroxides.

Further studies have also been conducted to measure the antioxidant power of astaxanthin. They estimate that the action of astaxanthin on singlet oxygen is:

• 6,000 times superior to Vitamin C;

• 790 times superior to coenzyme Q10;

• 110 times superior to Vitamin E;

• 5 times superior to beta-carotene.

• 65 times superior to Vitamin C;

• 54 times superior to beta-carotene;

• 21 times superior to synthetic astaxanthin;

• 14 times superior to Vitamin E.