Benefits
Traditional flavoring herb for May wine, syrups and desserts
Sweet woodruff has a long history in Central and Northern Europe as an aromatic plant, steeped in white wine for May wine (Maibowle) and used in syrups, soft drinks, desserts and herbal preparations. Today its main role is flavor and scent. A recent review found no convincing clinical evidence for any defined woodruff preparation.
Hay-like aroma that develops as the cut herb wilts and dries
Fresh woodruff holds most of its coumarin in bound forms (melilotosides); in one analysis 88% of the coumarin in woodruff was released from these sugar-bound precursors. Wilting and drying free the coumarin and the scent. Lab work also found that long drying lowers coumarin again as it evaporates from the dried herb.
Folk uses for digestion, coughs and unease, not tested in people
In European folk medicine the herb was taken by mouth for digestive complaints, coughs and anxiety, and applied to wounds. No human study of any of these uses was found, so they rest on tradition; a recent review of the plant also found no convincing clinical evidence.
Fewer pro-inflammatory immune cells in mouse cell tests (lab study)
In mouse bone marrow macrophages pushed toward a pro-inflammatory (M1) state, an ethanol extract of the Latvian woodruff line richest in phenolics at 250 and 500 micrograms per mL cut the M1 share from 23% to 16% and 13%. It did not shift cells toward the calming M2 type. These are cell findings, not effects in people.
Paw swelling in rats given an oral leaf extract (animal study)
In an older screening of Italian medicinal plants, summarized in a recent review, an ethanol extract of woodruff leaves given by mouth at 100 mg per kg reduced chemically induced paw swelling in rats by 25%. This is a single animal screening test and has not been followed up in people.
Bacterial adhesion features in lab tests of a leaf extract (in vitro)
In a lab study of six Polish folk herbs against a urinary strain of E. coli, woodruff extract was one of the weaker inhibitors of bacterial growth, yet at 5 mg per mL and above the bacteria lost a red blood cell clumping sign of adhesion fibers, and biofilm fell. Drinking woodruff has not been tested for any urinary outcome.
Mechanism of action
Coumarin released from melilotoside precursors
In the living plant, coumarin is stored mainly as cis- and trans-melilotoside. When cells are damaged by wilting, drying or crushing, glycosidase enzymes split off the sugar and the freed acid closes into coumarin. This is why the scent, and the coumarin dose, depend on harvest time, drying and preparation.
Coumarin metabolism in the human liver
Coumarin is well absorbed, and in most people the liver enzyme CYP2A6 turns most of it into harmless 7-hydroxycoumarin. A minor route through other CYP enzymes forms a reactive epoxide; this route is thought to drive the liver injury seen in a small subset of people, though CYP2A6 gene variants alone did not explain who was affected.
Iridoids and phenolics beyond coumarin
Woodruff also contains iridoid glycosides (monotropein, asperuloside, asperulosidic acid and others), chlorogenic and neochlorogenic acid, and quercetin and kaempferol glycosides such as rutin. These compounds are active in cell and animal studies, but how much a woodruff tea or wine supplies has not been linked to any effect in people.
Coumarin is not a blood thinner
Coumarin shares part of its name with the drug warfarin, sold as Coumadin, but they differ. Warfarin and dicumarol are vitamin K antagonist derivatives, while plain coumarin, the compound in woodruff, is described in a review of its toxicology as having no anticoagulant activity.
Clinical trials
Laboratory study of 70% ethanol extracts of wild, sun-grown and shade-grown woodruff from Latvia: chemical profiling, antioxidant tests and effects on mouse bone marrow-derived macrophages. One author works for a cultivation company that the paper says had no role in the study. (Razzivina et al. 2024, Antioxidants (Basel))
No human participants; macrophages cultured from mouse bone marrow, plus chemical assays.
Coumarin stayed fairly stable across growing conditions, while sun-grown plants had more phenolics (mainly chlorogenic acid and rutin) and stronger antioxidant activity. At 250 and 500 micrograms per mL the extract lowered the share of pro-inflammatory M1 macrophages from 23% to 16% and 13%, without raising M2 cells, and was not toxic to the cells up to 750 micrograms per mL.
Laboratory study of leaf extracts of birch, horsetail, rupturewort, sweet woodruff, nettle and lingonberry against a uropathogenic E. coli strain: growth, surface hydrophobicity, motility, adhesion fibers and biofilm. (Wojnicz et al. 2012, Urol Res)
No human participants; bacterial cultures.
Woodruff extract was among the weakest growth inhibitors of the six, though at 20 mg per mL bacterial survival fell to 37% of control. At 5 mg per mL and above the bacteria lost their red blood cell clumping ability, and like all six extracts it reduced biofilm, but it also increased swimming motility. Lab concentrations do not show any effect of drinking the herb.
Laboratory analysis of harvested woodruff shoots, measuring coumarin, cis-melilotoside and trans-melilotoside by UHPLC-DAD over 72 hours of drying, to examine the traditional pre-drying step for Maibowle. (Herre et al. 2025, Phytochemistry)
Harvested Galium odoratum plant material; no human or animal participants.
Drying was complete after 48 hours. trans-Melilotoside appeared to convert gradually to cis-melilotoside, and coumarin fell during longer drying because it sublimated, which the authors say supports using fresh or briefly air-dried herb with set drying times. Iridoids, chlorogenic acids and two flavonoid glycosides were also isolated. No intake or safety outcome was measured.