Astaxanthin, an antioxidant superior to beta-carotene?

Belonging to the carotenoid family, astaxanthin is a liposoluble pigment whose structure was first discovered by Professor Basil WEEDON in 1975. He determined that unlike other carotenoids, astaxanthin does not convert into vitamin A in the body, an interesting feature considering that an excess of vitamin A in the body can be harmful. Astaxanthin is obtained from unicellular algae, most often from the micro-algae Haematococcus pluvialis. In cosmetics, its INCI name is indeed Haematococcus Pluvialis Extract. It is also present in certain crustaceans and fish (shrimp, lobsters, crabs, lobsters, trout...) and is responsible for their red colouration.

Today, we find astaxanthin in many products where it is incorporated for its excellent antioxidant properties. These properties are based on the ability of this pigment to cross the cellular membrane. Indeed, the chemical structure of astaxanthin includes hydrophilic and lipophilic regions, which allows it to combine with the cellular membrane, from both the inside and outside. Thus, its polar groups overlap the external polar regions of the cellular membrane, while the non-polar central area of the molecule inserts itself into the internal non-polar region of the membrane.

Astaxanthin can therefore adopt a transmembrane alignment in biological membranes, assisting in maintaining membrane structure and reducing its fluidity. This enables it to act as a cellular shield to combat the spread of free radicals.

The astaxanthin is often compared to beta-carotene, with which it shares a similar linear polyenic chemical structure, with conjugated double bonds, giving them a high affinity for free radicals. However, the presence of polar functional groups at the ends of the astaxanthin significantly alters its biological properties. Unlike beta-carotene, astaxanthin can stably integrate into phospholipid membranes, with its polar ends interacting with intra- and extracellular aqueous environments, and its lipophilic central chain integrating into the membrane core. This arrangement gives the molecule an effective and lasting antioxidant shield role within the cell membranes themselves, unlike beta-carotene which cannot insert itself there.