It is a group of substances having similar biological activity.The first compound of this group was isolated from alfalfa and other from putrified fish meal.It is essential because of its role in synthesis of prothrombin and other blood clotting factors.
Chemical characterstics of vitamin K
Vitamin K1 (isolated from alfalfa) is called phylloquinone.
Vitamin K2 obtained from putrefied fish meal exists as a chemical series.
The naturally occuring substances in pure form are light yellow solids or oils,insoluble in water but soluble in fat solvents. Vitamin K compounds have characterstics absorption spectra in the ultraviloet and are sensitive to alkali,light and ionizing radiation.
Digestion and absorption of Vitamin K
More than half of the human requirement of vitamin K is met by the synthesis by symbiotic bacteria in the lower intestinal tract of the human body.
Extended treatment with anti-bacterial drugs that alter the enteric flora increases the dietary Vitamin K requirement in man since the useful symbiotic bacteria are destroyed.
Functions of Vitamin K
Prothrombinogen and other blood clotting factors are formed in the liver with the help of vitamin K. These factors are necessary for the clotting of blood. For newborn infants and especially those born premature, a single dose of 1 mg of vitamin K1 immediately after birth is often a routine measure to prevent haemorrhagic disease.
Deficiency of Vitamin K
Its deficiency interferes with the formation of prothrombinogen and thus reduces the clotting tendency of blood.In other words, the blood clotting time is prolonged.
A premature infant is sensitive to lack of this vitamin.
Sources of Vitamin K
It is widely distributed in nature. The green leafy vegetables,tomatoes, cauliflower,egg-yolk, soyabean oil and liver are good source.