Lanolin, also known as wool wax or wool grease, is a natural wax extracted from the sebaceous secretions of sheep's wool. It is classified as a simple lipid distinct from glycerides. This complex emollient mixture (~25-30% bound water) excels in occlusive moisturization, closely mimicking human sebum composition for dermatological applications.
Chemical Composition
Lanolin comprises approximately 97% high molecular weight esters and polyesters of sterols and triterpene alcohols (35-44%) combined with fatty acids (C7-C41, mainly palmitic C16:0, stearic C18:0, C20-C32), along with 11% free components including aliphatic alcohols (25%), sterols/cholesterol (two-thirds of alcohols), free acids, and hydrocarbons. More than 8,000–20,000 ester variants arise from around 200 acids and 100 alcohols (e.g., cholesterol, lanosterol), resulting in an average molecular weight of ~508.9 g/mol (C34H68O2 representative).
Physical Properties
Lanolin appears as an amber-yellow, unctuous solid (melting range 36–42°C, density ~0.94 g/cm³), insoluble in water yet dispersible in a 2:1 ratio with water. It softens at 38–40°C with high plasticity due to gauche CH₂ conformers. Solubility is high in chloroform and ether, sparing in alcohol. XLogP3 of 16.3 and TPSA of 26.3 Ų indicate extreme lipophilicity without hydrogen-bond donors.
Biosynthesis and Processing
Lanolin is secreted by sheep sebaceous glands as a water-repellent coat. Commercial extraction involves washing raw wool followed by centrifugal separation, refining (bleaching and deodorizing), and producing anhydrous lanolin (up to 99.8% lipids). Hydroxylation processes can yield water-soluble glycols for specific applications.
