Astaxanthin /æstəˈzænθɪn/ is a keto-carotenoid.[3][4] It belongs to a larger class of chemical compounds known as terpenes (as a tetraterpenoid) built from five carbon precursors, isopentenyl diphosphate, and dimethylallyl diphosphate. Astaxanthin is classified as a xanthophyll (originally derived from a word meaning “yellow leaves” since yellow plant leaf pigments were the first recognized of the xanthophyll family of carotenoids), but currently employed to describe carotenoid compounds that have oxygen-containing components, hydroxyl (-OH) or ketone (C=O), such as zeaxanthin and canthaxanthin. Indeed, astaxanthin is a metabolite of zeaxanthin and/or canthaxanthin, containing both hydroxyl and ketone functional groups.
Like many carotenoids, astaxanthin is a lipid-soluble pigment. Its red-orange colour is due to the extended chain of conjugated (alternating double and single) double bonds at the centre of the compound. This chain of conjugated double bonds is also responsible for the antioxidant function of astaxanthin (as well as other carotenoids) as it results in a region of decentralized electrons that can be donated to reduce a reactive oxidizing molecule.
Astaxanthin is a blood-red pigment and is produced naturally in the freshwater microalgae Haematococcus pluvialis and the yeast fungus Xanthophyllomyces dendrorhous (also known as Phaffia). When the algae is stressed by lack of nutrients, increased salinity, or excessive sunshine, it creates astaxanthin. Animals who feed on the algae, such as salmon, red trout, red sea bream, flamingos, and crustaceans (i.e. shrimp, krill, crab, lobster, and crayfish), subsequently reflect the red-orange astaxanthin pigmentation to various degrees.
The structure of astaxanthin by synthesis was described in 1975.[5] Astaxanthin is not converted to vitamin A in the human body so it is completely nontoxic if given orally.[clarification needed]
Astaxanthin can also be used as a dietary supplement intended for human, animal, and aquaculture consumption. The industrial production of astaxanthin comes from plant- or animal-based and synthetic sources. The U.S. Food and Drug Administration has approved astaxanthin as a food coloring (or color additive) for specific uses in animal and fish foods.[6] The European Commission considers it food dye and it is given the E number E161j.[7] Astaxanthin from algae, synthetic and bacterial sources, is generally recognized as safe (GRAS) by the FDA.[8][9] The European Food Safety Authority has set an Acceptable Daily Intake of 0.2 mg per kg body weight in 2019. [10] As a food color additive astaxanthin and astaxanthin dimethyldisuccinate are restricted for use in Salmonid fish feed only.[11]
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