Bafilomycin C1 is a member of a potent family of macrocyclic lactones. Bafilomycin C1 shares a similar mode of action and activity as its more accessible A1 analogue. Bafilomycin C1 is broadly active against bacteria, fungi, insects, nematodes and cestodes. Bafilomycin C1 has attracted interest as a potential agent for treating osteoporosis. The presence of the fumarate group provides an ideal ligand for affinity chromatography of V-ATPase.