Pyrroloquinoline quinone disodium salt (PQQ disodium salt, CAS 122628-50-6) is the water-soluble sodium salt form of pyrroloquinoline quinone, a redox cofactor and a novel vitamin-like compound. Its chemical structure features a planar, ortho-quinone fused with a pyrrole and a quinoline ring system, which is crucial for its electron transfer capabilities. PQQ is recognized as a potent antioxidant and a redox cofactor for several bacterial dehydrogenases. In mammalian systems, it is extensively studied for its role in promoting mitochondrial biogenesis, supporting cognitive function, and providing neuroprotective effects. Due to these properties, it is widely used as a key ingredient in dietary supplements, nutraceuticals, and functional foods aimed at enhancing energy metabolism and cellular health. Its status as a nutritional factor places it in the category of vitamins/coenzymes for research and commercial purposes. Beyond human nutrition, PQQ is also investigated in cosmetic formulations for its anti-aging and skin-protective benefits, leveraging its antioxidant activity. It is generally considered safe for consumption at recommended levels and is a subject of ongoing research into its full range of biological activities and health applications.