Astaxanthin

Astaxanthin is a ketocarotenoid pigment produced predominantly by the microalga Haematococcus pluvialis and accumulated through the food chain in crustaceans, salmon, and trout, accounting for their characteristic pink-red coloration. Its molecular structure — a polyene chain with carbonyl and hydroxyl groups on both ionone rings — enables it to span the full width of the lipid bilayer and scavenge singlet oxygen and free radicals more potently than many other carotenoids, including β-carotene. Unlike certain antioxidants, it does not act as a pro-oxidant at high concentrations under physiological conditions. Proposed mechanisms relevant to longevity include Nrf2 activation, NF-κB inhibition, mitochondrial protection, and modulation of inflammatory cytokines. Rodent studies show improvements in oxidative stress, immune parameters, and some cardiovascular markers; human RCTs are small and generally short-term, reporting modest effects on lipid oxidation biomarkers, skin aging, exercise-induced muscle damage, and inflammation. Synthetic astaxanthin (dominant in aquaculture) and natural algal-derived forms differ in esterification and stereochemistry, which may affect bioavailability. Evidence for direct human longevity benefit remains preliminary.