Coumarins in Plants

Properties and Effects

Coumarin, the simplest compound in its class, has a distinctive hay-like scent. In fresh plants, it exists as a glycoside bound to sugar, odorless until the plant wilts or dries, when the glycoside breaks down to release its characteristic aroma. Approximately one hundred coumarin compounds are known. Previously used in the food industry for flavoring, coumarin is no longer employed due to potential carcinogenic risks. Some coumarins offer health benefits, including anti-inflammatory effects, edema prevention, improved blood circulation, spasm relief, calming properties, and bactericidal action. However, high concentrations can damage the liver and heart and may have narcotic effects. Coumarins like esculetin, umbelliferone, and herniarin are used in sunscreens for their UV-absorbing properties, protecting against skin reddening.

Under bacterial influence, coumarin can transform into dicoumarol, which inhibits blood clotting by displacing vitamin K from enzyme complexes, preventing thrombosis. Modified forms of dicoumarol are used in cases of thrombosis risk. Some coumarins are strongly photosensitizing, causing herbal dermatitis. Contact with certain plants under sunlight can lead to red spots and blisters on the skin within hours, which may turn into dark spots after one or two days. Aflatoxins, a type of coumarin produced by molds on foods like grains, legumes, hazelnuts, and walnuts, are highly toxic, damaging the liver and posing carcinogenic risks. Avoiding moldy foods is essential to prevent exposure.