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Vitamin K
Chemical Structures
Food Sources
Vitamin K in the Body

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Vitamin K Crystals
Vitamin K2 Crystals
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Vitamin K

There are three forms of the fat soluble vitamin K. The first two, vitamin K1 (phylloquinone) and vitamin K2 (a group of compounds called menaquinones) are found naturally and the third, vitamin K3 (menadione) is a synthetic compound which is converted to vitamin K2 in the intestine. Vitamin K1 is 2-methyl-3-phytyl-1,4-naphthoquinone and is found in plants. The Menaquinones differ in the number of isoprene units in the side chain and in their degree of unsaturation, and are synthesised by bacteria in the human and animal intestines.


Chemical Structures

The Chemical Structure of Vitamin K1

Fig.1 The Chemical Structure of Vitamin K1 (phylloquinone)
3D Structure of Vitamin K1

The base structure of Vitamin K3

Fig.2 Menadione - The Base Structure of Vitamin K3


Principal Sources in Food

Principal dietary sources of vitamin K are:
  • Green leafy vegetables such as:
    • Spinach
    • Broccoli
    • Cabbage
  • Soya Beans
  • Liver
  • Green tea
  • Egg yolks
  • Oats
  • Whole wheat
  • Potatoes
  • Tomatoes
  • Asparagus
  • Butter
  • Cheese
Other sources include:
  • Some meats
  • Milk
  • Most Fruits
  • Many Vegetables

Vitamin K in the Body

Vitamin K is essential for blood clotting, as it is involved in production of the protein prothrombin, which converts soluble fibrinogen in the blood to insoluble fibrin which makes up the greater part of blood clots. Deficiency of vitamin K is rare due to the bacterial synthesis in the gut.



The vitamin K compounds are relatively stable to heat and reducing agents, but are sensitive to acid, alkali, light and oxidising agents.


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