Coumarin is a chemical compound (specifically, a benzopyrone) found in many plants, notably in high concentration in the tonka bean (Dipteryx odorata), vanilla grass (Anthoxanthum odoratum), woodruff (Galium odoratum), mullein (Verbascum spp.), and sweet grass (Hierochloe odorata). The name comes from a French word, coumarou, for the tonka bean. It has a sweet scent, readily recognised as the scent of newly-mown hay, and has been used in perfumes since 1882.
Although coumarin has no anticoagulant activity, it is transformed to the natural anticoagulant dicoumarol by a number of species of fungi. This proceeds through production of 4-hydroxycoumarin, then further (in the presence of naturally occurring formaldehyde) into the actual anticoagulant dicoumarol, a fermentation product and mycotoxin.[1]