Sterolien

Sterolien is the Dutch term for sterols, a class of lipids that share the cyclopentanoperhydrophenanthrene ring system and a hydroxyl group at position 3. They occur as free sterols or as sterol esters and are essential components of eukaryotic cell membranes, where they influence fluidity and permeability. They also serve as precursors to bile acids and steroid hormones.

In animals, cholesterol is the principal sterol. In plants, sitosterol, campesterol, and stigmasterol are predominant; fungi produce ergosterol. Sterol esters are common storage forms in seeds and in lipoproteins, where fatty acids are esterified to the hydroxyl group.

Biosynthesis occurs mainly via the mevalonate pathway, starting from acetyl-CoA; HMG-CoA reductase is a key regulatory enzyme. Sterol metabolism intersects with lipid transport and distribution in tissues.

Dietary aspects: plant sterols reduce intestinal cholesterol absorption and can modestly lower blood cholesterol in some individuals; cholesterol intake from animals affects risk of cardiovascular disease. However, sterols do not replace medical treatment as needed.

Analytical and ecological notes: sterol profiles are used in lipidomics, ecology, and paleobiology as taxonomic or biomass indicators. The composition of sterols varies across taxa and environments, reflecting biological and ecological processes.