Tetraterpenen

Tetraterpenen (English: tetraterpenes) are a class of isoprenoid compounds built from eight isoprene units and containing 40 carbon atoms (C40). They form a major group of naturally occurring pigments and lipophilic metabolites; the best-known members are the carotenoids, which include beta-carotene, lycopene, lutein and zeaxanthin.

Biosynthesis of tetraterpenes begins with the universal five-carbon building blocks isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), produced by the mevalonate or MEP pathways. Sequential condensations produce geranylgeranyl diphosphate (GGPP, C20), and two GGPP units are then joined by phytoene synthase to form phytoene (C40). Subsequent desaturation, cyclization and functionalization yield the structural diversity of tetraterpenes, including hydrocarbon carotenes and oxygenated xanthophylls.

Tetraterpenes are highly conjugated and hydrophobic, properties that give many of them strong color and antioxidant activity. In plants, algae and photosynthetic bacteria they function in light harvesting, photoprotection and as precursors of signaling molecules and vitamins (for example, beta-carotene as a provitamin A source). Non-photosynthetic microbes and some fungi also produce carotenoid-like tetraterpenes.

Commercially, tetraterpenes are used as natural food colorants, nutritional supplements and cosmetic ingredients. They are chemically and photochemically labile, requiring careful handling and formulation to preserve activity and color. Ongoing research explores their biosynthetic engineering, ecological roles and potential therapeutic applications.