Filipin III is a pentaene macrolide antibiotic and the predominant isomer of four isomeric polyene macrolides isolated from cultures of S. filipinensis. Due to Filipin III′s ability to fluoresce and bind to cholesterol, the compound has been used to detect cholesterol in membranes through freeze fracture electron microscopy and through decreased fluorescence of Filipin III upon binding. It has also been used in tobacco cells and observed to activate ligand-independent signaling responses. Through Filipin III′s cholesterol sequestering activity, it can disrupt the lipid rafts in both normal and transformed keratinocytes resulting in inhibition of the AKT pathway. Filipin III is the major component of 8 isomeric components in filipin.