ABSTRACT
Vitamin K has garnered much attention in recent years due to the ux of newer oral anticoagulant medications that could be substituted for warfarin, a vitamin K antagonist (VKA). Concurrently, research in the last few years has also helped in better understanding of the various other physiological roles of this vital trace element. Danish biochemist Henrik Dam is credited with the discovery of vitamin K. He observed that chickens fed with low-fat and sterol-free diets developed a syndrome of spontaneous subcutaneous and intramuscular hemorrhage.1 The quest for isolating the ingredient that caused this deciency syndrome led him to discover that it was fat soluble. Doisy delineated the biochemistry of vitamin K: vitamin K1 (phylloquinone) present in green plants, and vitamin K2 (menaquinones) produced by bacterial action.2 In 1943, Dam and Doisy shared the Nobel Prize in Physiology or Medicine for the discovery of vitamin K and its chemical nature. Naphthoquinone is the functional group of all compounds with the vitamin K cofactor activity, so that the mechanism of action is similar for all K vitamins. The different lipophilicity of the various side chains leads to differences in intestinal absorption, transport, tissue distribution, and bioavailability. Synthetic derivatives called vitamin K3 are water soluble and bypass the natural utilization in the body.
