[1] Coumarin is a colorless crystalline solid with a sweet odor resembling the scent of vanilla and a bitter taste.

While coumarin is not an anticoagulant, its 3-alkyl-4-hydroxy derivatives, such as the fungal metabolite dicoumarol, inhibit synthesis of vitamin K, a key component in blood clotting.

[2] A related compound, the prescription drug anticoagulant warfarin, is used to inhibit formation of blood clots, deep vein thrombosis, and pulmonary embolism.

[5][6] Also in 1820, Nicholas Jean Baptiste Gaston Guibourt (1790–1867) of France independently isolated coumarin, but he realized that it was not benzoic acid.

[7] In a subsequent essay he presented to the pharmacy section of the Académie Royale de Médecine, Guibourt named the new substance coumarine.

[citation needed] In humans, the enzyme encoded by the gene UGT1A8 has glucuronidase activity with many substrates, including coumarins.

Some of the 4-hydroxycoumarin anticoagulant class of chemicals are designed to have high potency and long residence times in the body, and these are used specifically as rodenticides ("rat poison").

[31] European health agencies have warned against consuming high amounts of cassia bark, one of the four main species of cinnamon, because of its coumarin content.

[32][33] According to the German Federal Institute for Risk Assessment (BFR), 1 kg of (cassia) cinnamon powder contains about 2.1 to 4.4 g of coumarin.

One teaspoon of cassia cinnamon powder therefore contains 5.8 to 12.1 mg of coumarin, which may be above the tolerable daily intake value for smaller individuals.

[37] Coumarin is currently listed by the Food and Drug Administration (FDA) of the United States among "Substances Generally Prohibited From Direct Addition or Use as Human Food," according to 21 CFR 189.130,[38][39] but some natural additives containing coumarin, such as the flavorant sweet woodruff are allowed "in alcoholic beverages only" under 21 CFR 172.510.

[40] In Europe, popular examples of such beverages are Maiwein, white wine with woodruff, and Żubrówka, vodka flavoured with bison grass.

In conclusion, researchers stated, "The results suggest that coumarins have an influence on the development of the brain which can lead to mild neurologic dysfunctions in children of school age.