coumarin

noun

cou·​ma·​rin ˈkü-mə-rən 

: a toxic white crystalline lactone C₉H₆O₂ with an odor of new-mown hay found in plants or made synthetically and used especially in perfumery and as a parent compound in anticoagulant agents

also : a derivative of this compound

Examples of coumarin in a Sentence

Recent Examples on the Web

Over time, large amounts of coumarin can cause liver damage.14 Talk with your healthcare provider and do not exceed 1 gram per day without medical guidance. —Carrie Madormo, Verywell Health, 19 Jan. 2026

But Cassia cinnamon also contains a compound called coumarin, which can cause liver damage if it's consumed in large amounts. —Sarah Bradley, Health, 11 Dec. 2025

The scent features a molecule that can only be activated in sunlight, allowing for notes of coumarin to come out during the day. —Emily Burns, Footwear News, 4 Dec. 2025

When scientific studies proved that coumarin caused liver damage in animals, the US Food and Drug Administration moved to ban the tonka bean as a food ingredient in 1954. —JSTOR Daily, 15 Nov. 2025

Word History

Etymology

French coumarine, from coumarou tonka bean tree, from Spanish or Portuguese; Spanish cumarú, from Portuguese, from Tupi *kumarú, *kumbarú

First Known Use

1830, in the meaning defined above

Medical Definition

coumarin

noun

cou·​ma·​rin ˈkü-mə-rən 

: a toxic white crystalline lactone C₉H₆O₂ with an odor of new-mown hay found in plants or made synthetically and used especially in perfumery and as the parent compound in various anticoagulant agents (as warfarin)

also : a derivative of this compound