Annonacin (Ann)

Annonacin is a chemical found in some fruits such as the custard apple and soursop (and others from the family Annonaceae). It is a member of the class of compounds known as acetogenins. Some reports concluded that regular consumption in rats (3.8 and 7.6 mg per kg per day for 28 days) caused brain lesions consistent with Parkinson's disease.
Along with other acetogenins, annonacin is reported to block mitochondrial complex I (NADH-dehydrogenase), which is responsible for the conversion of NADH to NAD+ and the build-up of a proton gradient over the mitochondrial inner membrane. This effectively disables a cell's ability to generate ATP via an oxidative pathway, ultimately forcing a cell into apoptosis or necrosis.