The MitoTox™ Complex I Activity Kit (MT-OX1) is designed for screening the direct inhibitory effect of compounds on Complex I activity and does this using enzyme immunocaptured from bovine heart mitochondria. Bovine heart mitochondria are provided in this kit as they are a rich source of Complex I. The phospholipids provided in the kit are essential for rotenone-sensitive Complex I activity, rotenone being a well-known inhibitor of Complex I.