phylloquinon

Phylloquinon, also known as phylloquinone or vitamin K1, is a fat-soluble vitamin and the primary form of vitamin K obtained from plants. Its chemical structure features a naphthoquinone ring with a long phytyl side chain. Phylloquinon is the major plant-derived vitamin K and is complemented in the body by menaquinones (vitamin K2) produced by gut bacteria.

Functionally, phylloquinon serves as a cofactor for the enzyme gamma-glutamyl carboxylase, enabling the carboxylation of specific glutamate residues in vitamin K–dependent proteins. This modification allows these proteins to bind calcium, which is essential for blood coagulation. Key vitamin K–dependent proteins include coagulation factors II (prothrombin), VII, IX, and X, as well as proteins C and S. In addition to coagulation, phylloquinon is involved in bone metabolism and may influence vascular health, though details of these roles are less well defined.

Dietary sources and metabolism: Phylloquinon is abundant in leafy green vegetables such as spinach, kale, and broccoli, and is present in some vegetable oils. It is absorbed with dietary fat, transported via chylomicrons, and stored primarily in the liver. The gut microbiota also produces menaquinones, but phylloquinon remains the predominant plant-derived form.

Intake, safety, and deficiency: General recommendations for adults are about 120 micrograms per day for men and 90 micrograms per day for women, though values vary by country. Deficiency is rare but can occur with fat malabsorption or in newborns, who typically receive vitamin K at birth to prevent hemorrhagic disease. Phylloquinon interacts with anticoagulants such as warfarin, and large increases can affect anticoagulation control. There is no established upper intake limit, and toxicity from phylloquinon is rare.