Coenzyme pyrroloquinoline quinone (PQQ) is an important molecule in biology, chemistry and engineering. It has 14 kinds of carbon atoms, and there are 14 peaks in DMSO-d6 on the 13C-NMR measurement. The disodium salt of PQQ (Na2PQQ), used as food, is not dissolved in DMSO. A 13C-NMR assignment of Na2PQQ in deuterium oxide has not been reported. As for the measurement with a high sensitivity detector (cryo detector), 28 peaks could be observed in deuterium oxide. A quantum chemical calculation revealed that it has two states in equilibrium with the acetal structure by the addition of water to the quinone moiety.