25-Hydroxy Cholesterol

25-Hydroxy Cholesterol is a sterol derivative featuring a cyclopentanoperhydrophenanthrene nucleus with hydroxyl groups at C-3 and C-25 positions. The introduction of the 25-hydroxyl substituent introduces steric hindrance and alters hydrogen bonding capacity compared to parent cholesterol. This positional isomer exhibits distinct physicochemical properties due to the exocyclic hydroxyl's spatial orientation relative to the steroid A-ring. Its unique polarity enables separation from cholesterol via normal-phase chromatography. Serves as an HPLC reference standard for quantifying cholesterol oxidation byproducts in pharmaceutical synthesis.