PQQ is a redox cofactor that plays a significant role in mitochondrial function and cellular energy metabolism. It is a small quinone molecule found in various foods—notably fermented soybeans, spinach, green tea, and kiwi. However, the modern diet may not provide sufficient amounts of this essential nutrient, leading many to seek out PQQ supplements. PQQ has garnered attention not only for its role in energy production but also for its potential neuroprotective and antioxidant properties.