Category: vitamin
Aliases: Vitamin K3, 2-methyl-1,4-naphthoquinone, Menaphthone
Synthetic naphthoquinone lacking the isoprenoid side chain. Serves as a circulating precursor for tissue menaquinone-4 (MK-4): extrahepatic UBIAD1 prenyltransferase geranylgeranylates menadione to MK-4 in pancreas, testis, and brain. Menadione itself is redox-active and undergoes semiquinone cycling that can deplete glutathione and generate hydrogen peroxide — this is why synthetic K3 caused hemolytic anemia and kernicterus in neonates and was withdrawn from human OTC use (FDA ban 1963). Still used in animal feed and as a research tool.
PO: 0.45h