PQQ was originally thought to be a bacterial cofactor. Under appropriate conditions, PQQ is able to catalyze continuous redox cycles (the ability to catalyze repeated oxidation and reduction reactions) as well as oxidative deamination (Rucker et al., 2009), so it can act as an antioxidant (Rucker et al. 2009). ). There is strong evidence that PQQ may play an important role in pathways important for cell signaling. PQQ also acts as an antioxidant. The importance of PQQ to mammalian health is evident when PQQ is omitted from the chemically defined diet. PQQ has a variety of physiological effects, such as promoting growth and reproduction, and providing neurological and cardiovascular protection. It also enhances antioxidants, learning, memory, and immune function (Rucker et al., 2009). PQQ disodium salt is thought to have similar physiological and metabolic effects to PQQ.