FILIPIN is a complex of polyene macrolides obtained from Streptomyces filipinensis. The complex consists of four components: filipin I (4%), II (25%), III (53%), and IV (18%). Filipin III alters membrane function by interfering with membrane sterols, inhibits mitochondrial respiration, and is proposed as an antifungal agent. It is widely used as a marker for detection and quantification of cholesterol in cellular membranes.