Coumarin (Molecule of the Month for April 2019)
Coumarin is a colorless crystalline solid, with a sweet odor resembling the scent of vanilla and bitter taste. It is found in many plants, where it may serve as a chemical defense against predators. Coumarin is derived from coumarou, the French word for the tonka bean. The word tonka for the tonka bean is taken from the Galibi (Carib) tongue spoken by natives of French Guiana (one source for the plant); it also appears in Old Tupi, another language of the same region, as the name of the tree. Coumarin is found naturally in many plants, notably in high concentration in the tonka bean (Dipteryx odorata). It also occurs in vanilla grass (Anthoxanthum odoratum), sweet woodruff (Galium odoratum), sweet grass (Hierochloe odorata) and sweet-clover (genus Melilotus), which are named for the sweet (i.e., pleasant) smell of the compound. Coumarin is found naturally also in many edible plants such as strawberries, black currants, apricots, and cherries.
Coumarin has appetite-suppressing properties, which may discourage animals from eating plants which contain it. Though the compound has a pleasant sweet odor, it has a bitter taste, and animals tend to avoid it. Coumarin is often found in artificial vanilla substitutes, despite having been banned as a food additive in numerous countries since the mid-20th century. It is still used as a legal flavorant in soaps, rubber products, and the tobacco industry, particularly for sweet pipe tobacco and certain alcoholic drinks. Coumarin is moderately toxic to the liver and kidneys, with a median lethal dose (LD50) of 275 mg/kg, a low toxicity compared to related compounds. Though it is only somewhat dangerous to humans, coumarin is hepatotoxic in rats, but less so in mice.
Coumarin was banned as a food additive in the United States in 1954, largely because of the hepatotoxicity results in rodents. 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, but some natural additives containing coumarin, such as the flavorant sweet woodruff are allowed "in alcoholic beverages only" under 21 CFR 172.510. In Europe, popular examples of such beverages are Maiwein, white wine with woodruff, and Żubrówka, vodka flavoured with bison grass.
Formal Chemical Name (IUPAC)
Update by Karl Harrison
(Molecule of the Month for April 2019 )
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