Also Known As: Vitamin K1, Phylloquinone, Mephyton
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, particularly leaves, since it functions as an electron acceptor during photosynthesis, forming part of the electron transport chain of Photosystem
Vitamin K is a group of structurally similar, fat-soluble vitamins that are needed for the posttranslational modification of certain proteins required for blood coagulation and in metabolic pathways in bone and other tissue. They are 2-methyl-1,4-naphthoquinone (3-) derivatives. This group of vitamins includes two natural vitamers: vitamin K1 and vitamin K2.
Vitamin K1 is also known as vitamin Kj, phylloquinone or phytomenadione (also called phytonadione). Vitamin K1 is required for blood coagulation and is synthesized by plants, is found in green leafy vegetables, and can be found in soybean oil.
Vitamin K2 is involved in bone metabolism. Vitamin K2 homologs (menaquinones) are characterized by the number of isoprenoid residues comprising the side chain. Menaquinones are abbreviated MK-n, where n represents the number of isoprenoid side chains. Thus, menaquinone-4 abbreviated MK-4, has 4 isoprene residues in the side chain. Bacteria can produce a range of vitamin K2 forms, including the conversion of K1 to K2 (MK-7) by bacteria in the small intestines. No known toxicity exists for vitamins K1 and K2.
Three synthetic types of vitamin K are known: vitamins K3, K4, and K5. Although the natural K1 and K2 forms are nontoxic, the synthetic form K3 (menadione) has shown toxicity.