Cyclopiazonic acid is a toxic fungal secondary metabolite

Secondary metabolite

Secondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of an organism. Unlike primary metabolites, absence of secondary metabolities does not result in immediate death, but rather in long-term impairment of the organism's...

. 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

Aspergillus flavus

Aspergillus flavus is a fungus. It is a common mold in the environment, and can cause storage problems in stored grains. It can also be a human pathogen, associated with aspergillosis of the lungs and sometimes causing corneal, otomycotic, and nasoorbital infections. Many strains produce...

and Aspergillus versicolor.

Cyclopiazonic acid only appears to be toxic in high concentrations.

Biologically, Cyclopiazonic acid is a specific inhibitor of Ca²⁺-ATPase

SERCA

SERCA, or sarco/endoplasmic reticulum Ca2+-ATPase, or SR Ca2+-ATPase, is a calcium ATPase-type P-ATPase.-Function:SERCA resides in the sarcoplasmic reticulum within muscle cells...

in the intracellular Ca²⁺ storage sites.