Subclass of Phenolics

Coumarins

Fragrant benzopyrone compounds with anticoagulant, antispasmodic, and vaso-protective activity.

Overview

About Coumarins

Coumarins are benzopyrone compounds — a benzene ring fused to a lactone — formed when a hydroxycinnamic acid cyclizes onto itself. The parent compound gives new-mown hay and sweet woodruff their characteristic scent, which appears only as the plant dries and the bound precursor is released.

The group carries a reputation it only partly deserves. Coumarin itself is not an anticoagulant; the anticoagulant is dicoumarol, a fungal spoilage product formed when coumarin-rich sweet clover moulds — a distinction worth getting right before reading anything else about the class.

Where Coumarins Occur

Concentrated in a handful of families, notably the umbellifers, citrus and legumes:

Sweet woodruff, tonka bean, cassia cinnamon

coumarin itself

Angelica, ammi and hogweed (Apiaceae)

imperatorin, xanthotoxin, bergapten

Grapefruit and bergamot

bergapten and the furanocoumarins

Horse chestnut and many barks

aesculin, scopoletin, fraxin

Sweet clover, when spoiled

dicoumarol

Furanocoumarins & Phototoxicity

The furanocoumarins carry an extra fused furan ring and are the members that most affect people. On skin, they intercalate into DNA and, on ultraviolet exposure, cross-link it — producing phytophotodermatitis, the burn-like blistering that follows handling giant hogweed, wild parsnip or lime juice in sunlight.

That same reaction is used deliberately: PUVA therapy pairs a psoralen with UVA light to treat psoriasis and vitiligo. Furanocoumarins are also the mechanism behind the grapefruit-juice drug interaction, irreversibly inhibiting intestinal CYP3A4 and raising blood levels of a long list of medicines.

Pharmacological Importance

Beyond the phototoxic members, the class supplies genuinely useful constituents: aesculin and related coumarins support venous tone and capillary integrity in horse chestnut preparations, scopoletin is antispasmodic, and osthole has a broad preclinical anti-inflammatory literature.

The coumarin scaffold has also been productive in drug design — warfarin descends directly from dicoumarol.

Toxicity & Safety

Coumarin itself is hepatotoxic in susceptible individuals, which is why regulators cap it in food and why cassia cinnamon — high in coumarin — carries intake guidance that Ceylon cinnamon does not.

Furanocoumarin-bearing herbs and oils demand sun avoidance after use, topically and internally. And the persistent belief that coumarin-containing plants thin the blood should be resisted: it confuses the plant compound with the fungal metabolite and with the synthetic drug derived from it.

Constituents

All Coumarins

38 total Filter coumarins

Open in filterable index

Source Plants

Herbs Containing Coumarins

35 herbs

Plants in the materia medica documented to carry coumarins, with the compounds each one is listed for. The bar counts how many DISTINCT coumarins are on record for a plant, relative to the best-documented — it measures breadth of record, not potency, so a plant with one well-studied compound can outrank a richer source that has simply been analysed less. Where a measured concentration is on record it is quoted inline; most entries have none yet.