Astaxanthin

Astaxanthin is a red-pigmented carotenoid (C₄₀H₅₂O₄) produced naturally by micro-algae, yeast, and certain marine organisms. It is widely taken as a dietary supplement because its potent antioxidant properties can protect cellular membranes from oxidative damage, supporting overall health and performance.

• Molecular Formula and Weight: Astaxanthin is a xanthophyll carotenoid with the molecular formula C₄₀H₅₂O₄ and a molecular weight of 596.84 g mol⁻¹.
• IUPAC Name: Its IUPAC name is (3R,3′R,5R,5′R)-3,3′-dihydroxy-β,β′-carotene-4,4′-dione.
• Molecular Structure: The molecule consists of a linear 13-conjugated double-bond polyene chain flanked by two β-ionone rings each bearing a hydroxyl group at C-3 and a keto group at C-4, giving it polar ends and a non-polar central region.
• Amphiphilic Properties: This amphiphilic architecture enables insertion into lipid bilayers with the polar ends oriented toward aqueous phases, stabilizing membrane integrity.
• Stereoisomers: The compound exists as three stereoisomers; the natural form is the 3S,3′S,5R,5′R (all-trans) isomer, which shows the highest bioactivity.
• Solubility: Its solubility is low in water (<0.1 µg/mL) but high in organic solvents (e.g., ethanol, acetone) and in lipid carriers, which drives the need for fat-based formulation in supplements.

• Primary Source: Commercial astaxanthin is principally derived from the micro-alga Haematococcus pluvialis, cultured under high-light, nutrient-limited conditions that trigger carotenoid accumulation.
• Alternative Sources: Alternative natural sources include shrimp, krill, and salmon, though the yields are low and extraction is cost-inefficient.
• Synthetic Production: Industrially, astaxanthin is also produced synthetically (e.g., algal-fermented yeast Phaffia rhodozyma or chemically via condensation of C₁₀-C₁₀ units).
• Natural vs. Synthetic: The natural (algal) form is chemically identical to the synthetic, but the former contains the all-trans stereoisomer, which is considered more bio-active.
• Extraction Methods: High-quality supplements employ supercritical CO₂ extraction, preserving the all-trans configuration and minimizing solvent residues.
• Quality Criteria: Quality criteria include: ≥ 70 % trans-isomer purity, absence of heavy metals, and verification of antioxidant activity (e.g., ORAC > 250,000 µmol TE/100 g).
• Certifications: Third-party certifications (e.g., USP, NSF) help ensure potency and purity for consumer use.