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
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
Watch out for coumarin: Cassia cinnamon (Cinnamomum cassia) contains coumarin, a chemical that may harm your liver when consumed in large amounts for prolonged periods or with liver conditions.1
Food-level amounts are generally safe: Cinnamon consumed in amounts used in foods is likely safe.
—Jamie Johnson, Verywell Health, 17 Oct. 2025
For example, cinnamon contains powerful antioxidant and anti-inflammatory compounds, including cinnamaldehyde, eugenol, cinnamic acid, and coumarin, that may help lower inflammation and protect cells against oxidative stress.
—Jillian Kubala, Health, 14 Oct. 2025
The scientists started with a molecule derived from the natural compound coumarin, and chemically linked it to the component of penicillin that kills bacteria by destroying their cell walls.
—Ben Coxworth, New Atlas, 13 June 2025
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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
Watch out for coumarin: Cassia cinnamon (Cinnamomum cassia) contains coumarin, a chemical that may harm your liver when consumed in large amounts for prolonged periods or with liver conditions.1
Food-level amounts are generally safe: Cinnamon consumed in amounts used in foods is likely safe.
—Jamie Johnson, Verywell Health, 17 Oct. 2025
For example, cinnamon contains powerful antioxidant and anti-inflammatory compounds, including cinnamaldehyde, eugenol, cinnamic acid, and coumarin, that may help lower inflammation and protect cells against oxidative stress.
—Jillian Kubala, Health, 14 Oct. 2025
The scientists started with a molecule derived from the natural compound coumarin, and chemically linked it to the component of penicillin that kills bacteria by destroying their cell walls.
—Ben Coxworth, New Atlas, 13 June 2025
Cite this Entry
“Coumarin.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/coumarin. Accessed 14 Dec. 2025.
Copy CitationMedical 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
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