It is a fat-soluble vitamin that is stable to air and moisture but decomposes in sunlight. It is found naturally in a wide variety of green plants, particularly leaves, since it functions as an electron acceptor during photosynthesis, forming part of the electron transport chain of Photosystem I.
|Jmol-3D images||Image 1|
|Molar mass||450.7 g mol−1|
It is often called vitamin K1, phytomenadione or phytonadione. Sometimes a distinction is made with phylloquinone considered natural and phytonadione considered synthetic.
A stereoisomer of phylloquinone is called vitamin k1 (note the difference in capitalization).
Its best-known function in animals is as a cofactor in the formation of coagulation factors II (prothrombin), VII, IX, and X by the liver. It is also required for the formation of anticoagulant factors protein C and S. It is commonly used to treat warfarin toxicity, and as an antidote for coumatetralyl.
Vitamin K is also required for bone protein formation.