Cyclopiazonic acid (CPA) is a toxic fungal secondary metabolite. Chemically, it is an indole tetramic acid.
CPA was originally isolated from Penicillium cyclopium and subsequently from other P. cyclopium, Penicillium griseofulvum, Penicillium camembertii, Aspergillus flavus and Aspergillus versicolor.
Cyclopiazonic acid only appears to be toxic in high concentrations.
Biologically, Cyclopiazonic acid is a specific inhibitor of Ca2+-ATPase in the intracellular Ca2+ storage sites.