Phylloquinone is a polycyclic

Polycyclic compound

In organic chemistry, a polycyclic compound is a cyclic compound with more than one hydrocarbon loop or ring structures . In general, the term includes all polycyclic aromatic compounds, including the polycyclic aromatic hydrocarbons, the heterocyclic aromatic compounds containing sulfur,...

 aromatic ketone

Ketone

In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...

, based on 2-methyl-1,4-naphthoquinone, with a 3-phytyl

Phytane

Phytane is a diterpenoid alkane. In contrast to pristane, which is formed from the decarboxylation of phytol, it has one extra carbon.Phytanyl is the corresponding substituent. Phytanyl groups are frequently found in phospholipids in membranes of thermophilic Archaea...

 substituent

Substituent

In organic chemistry and biochemistry, a substituent is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon...

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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.

Terminology

It is often called vitamin K₁ 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).

Mechanism

Its best known mechanism of action is as a cofactor in the formation of coagulation factors II (prothrombin), VII, IX and X by the liver. Vitamin K₁ is commonly used to treat warfarin

Warfarin

Warfarin is an anticoagulant. It is most likely to be the drug popularly referred to as a "blood thinner," yet this is a misnomer, since it does not affect the thickness or viscosity of blood...

 toxicity, and an antidote for coumatetralyl

Coumatetralyl

Coumatetralyl is an anticoagulant of the warfarin type. Symptoms of overexposure relate to failure of the blood clotting mechanism and include bleeding gums and failure of blood clotting after skin wounds. After one exposure the toxicity of coumatetralyl is relatively low, however if overexposure...

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It is also required for the formation of anticoagulant factors protein C and S.
Vitamin K is also required for bone protein formation.

Phylloquinone is an electron acceptor in the electron transport chain of chloroplasts.