Pyrroloquinoline quinone (PQQ), with the chemical formula C14H6N2O8 and a molecular weight of 330.206, is an aromatic ortho-quinone compound. It is reddish-brown in appearance, readily soluble in water, and decomposes easily under light. Its isoelectric point is 2.75, and its melting point is 250°C.

PQQ is relatively stable to heat and exhibits a unique green fluorescence. Under weakly acidic and neutral conditions, it readily dissociates into anions, which can combine with many compounds such as water, alcohols, aldehydes, ketones, ammonia, amines, boric acid, and cyanides to form corresponding adducts. In living organisms, PQQ exists in three forms—quinone (PQQ), semiquinone (PQQ), and hydroquinone (PQQH2)—depending on the binding of electrons and hydrogen ions. Its high redox potential ensures efficient electron transfer, making it a highly efficient coenzyme. Besides naturally occurring forms, PQQ can also be biosynthesized in vivo by specific gene clusters.

Application

Stimulating Microbial Cell Growth: PQQ stimulates microbial growth in two ways: first, it shortens the lag phase of bacterial cells, similar to essential growth factors, accelerating cell growth and increasing cell yield with increasing concentration; second, it shortens the lag phase without affecting the cell growth rate.

Stimulating Plant Cell Growth: By shortening the growth arrest phase, PQQ stimulates plant growth. It also promotes plant growth by enhancing the synthesis of auxins and cytokinins, thus promoting molecular-level gene regulation and improving plant cell metabolism.

Stimulating Human Cell Growth: Low concentrations of PQQ (0.003–30 μM) significantly enhance DNA synthesis in human fibroblasts and significantly increase cell density.