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|Section2= }} 4-Hydroxycoumarins are a class of vitamin K antagonist (VKA) anticoagulant drug molecules derived from coumarin (chromen-2-one) by adding a hydroxy group at the 4 position to obtain "4-hydroxycoumarin" (or "4-hydroxychromen-2-one"; formally then renumbered as 2-hydroxychromen-4-one), then adding a large aromatic substituent at the 3-position (the ring-carbon between the hydroxyl and the carbonyl). The large 3-position substituent is required for anticoagulant activity. The primary mechanism of the 4-hydroxycoumarin drugs is the inhibition of vitamin K epoxide reductase. These compounds are not direct antagonists (in the pharmaceutical sense) of vitamin K, but rather act to deplete reduced vitamin K in tissues. For this reason vitamin K antagonizes their effect, and this has led to the loose terminology of vitamin K antagonism. ==Origin== Although 4-hydroxycoumarin itself is not an anticoagulant, it is an important fungal metabolite from the precursor coumarin (also not an anticoagulant), and its production leads to further fermentative production of the natural anticoagulant dicoumarol. This happens in the presence of naturally occurring formaldehyde, which allows attachment of a second 4-hydroxycoumarin molecule through the linking carbon of the formaldehyde, to the 3-position of the first 4-hydroxycoumarin molecule, to give the semi-dimer the motif of the drug class. Dicoumarol appears in spoiled sweet clover silages and is considered to be a fermentation product and mycotoxin.〔Bye, A., King, H. K., 1970. The biosynthesis of 4-hydroxycoumarin and dicoumarol by Aspergillus fumigatus Fresenius. Biochemical Journal 117, 237-245.〕 After its identification in 1940, it became the historical prototype of this drug class. See warfarin for this history. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「4-Hydroxycoumarins」の詳細全文を読む スポンサード リンク
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