Sweet woodruff

Sweet Woodruff (Galium odoratum): A Comprehensive Reference

1. Identity, Taxonomy, and Botanical Description

Names and Classification

Galium odoratum (L.) Scop. (synonym: Asperula odorata L.) belongs to the family Rubiaceae and is commonly known as sweet woodruff. It is naturally distributed in Northern and Central Europe, Siberia, Northern Africa, and various regions in the north of Iran. Sweet woodruff is a flowering herbaceous perennial in the coffee family and is native to north Africa, Asia, and Europe. It was formerly placed in the genus Asperula in the family Rubiaceae.

Among its many common names are: sweet-scented bedstraw, herb walter, kiss-me-quick, master of the forest, master of the woods, our lady's lace, Waldmeister, wood rove, and wuderove. It is very popular in Germany where it is called Waldmeister, or Master of the Forest.

Botanical Characteristics

It is a perennial herbaceous plant that grows between 10 and 35 cm in height and has an erect, four-angled stem. The lower leaves are arranged in false whorls of five to seven leaves, whereas the upper leaves are arranged in whorls of eight, narrowing at the base. The flowers are white and form spike-like inflorescences at the top of the stem, but can also be found in the axils of the leaves in the lower whorls. The fruits are 2–4 mm in diameter, produced singly, and each is covered in tiny, hooked bristles, which help disperse them by sticking temporarily to clothing and animal fur.

The plant leaves are notable for their strong fragrance, which resembles the scent of freshly mown hay when the foliage is either crushed or cut. The fresh plant has little scent, but as it dries it becomes very aromatic, retaining the smell for years. It owes its sweet smell to the presence of the compound coumarin.

The genus name comes from the Greek word gala meaning milk, as the flowers were used to curdle milk in cheese making. The leaves and foliage were also used as a fragrant mattress and pillow stuffing, hence the common name bedstraw.

Geographic Distribution

Sweet woodruff (G. odoratum) is native to northern and central Europe, North Africa, and Siberia. It is sparingly naturalized in southern Canada and the northern United States. It was introduced in some locations in the USA including Colorado, Illinois, Minnesota, New York, and Vermont.

Common Forms and Preparations

Sweet woodruff is commercially and traditionally available in several forms:

• The dried herb has been used for centuries as a strewing herb, for potpourri or as a perfume ingredient, as a tonic in tea, and as an ingredient in German May Wine or a punch made with white wine, the herb, and strawberries.
• An infusion of the aerial parts is used in herbal practice for the treatment of insomnia, nervous tension, varicose veins, biliary obstruction, hepatitis, and jaundice.
• Herbalists have also pounded it into a poultice to heal wounds and bruises.
• Dried leaves and flowers can be used for potpourri and as a household insect repellant. It was often used in linen cupboards to protect against moth damage.
• The leaves and stems can be used to make tan or grey-green dyes, while the roots produce a red dye.

2. Traditional and Historical Use

Medieval and Early Modern European Herbalism

Sweet woodruff has been considered a medicinal and aromatic plant since the Middle Ages, mainly in European countries. It was widely used in herbal medicine during the Middle Ages, gaining a reputation as an external application to wounds and cuts and also taken internally in the treatment of digestive and liver problems.

The herb has been used by humans for well over a thousand years. Medieval European records describe sweet woodruff being gathered from woodlands for strewing on floors, stuffing into mattresses, and hanging in homes to repel moths and freshen the air. Monastery herbalists cultivated it in physic gardens for its reputed ability to treat liver and stomach complaints, and as a mild sedative when placed inside pillows.

For historical information on the usage of sweet woodruff, see Rembert Dodoens' A Nievve Herbal, written in 1554 and reprinted in English in 1578. In Britain, sweet woodruff was traditionally favoured more for its scent, which is often described as like freshly-mown hay and vanilla. Consequently it was used as a strewing herb from at least the 1300s onwards.

Traditionally, it has been used as a gentle calming herb, a digestive bitter-aromatic, a mild urinary support plant, and an external herb for swelling, irritated skin, and slow-healing tissues.

This herb was used to cure wounds, and some people mixed it with wine to reduce heartburn. Sweet woodruff was widely used as an external application to wounds and cuts.

The flowering tops and aerial parts are traditionally used to treat circulation and venous disorders, jaundice, hemorrhoids, and nervous agitation, and the crushed leaves have been topically used to reduce swelling.

It is traditionally used to treat digestive and bladder disorders, hepatitis, and nervousness. Some of its therapeutic values are listed in the French and Polish Pharmacopoeia, but their properties are not yet fully elucidated as research is ongoing.

The German Maibowle (May Wine) Tradition

May wine, also known as Maiwein or Maibowle, is a traditional German beverage originating from Central Europe, legally defined in the European Union as an aromatized wine obtained from white wine with added Galium odoratum (sweet woodruff, or Waldmeister in German), having an alcohol content of 7–18% vol.

The tradition traces its roots to medieval Europe, with the first documented mention in 854 AD by the monk Wandalbertus, who described a woodruff-infused wine as a medicinal tonic; sweet woodruff was valued as a strewing herb for its fresh, hay-like scent from coumarin compounds and believed to aid digestion and vitality. Since at least the 13th century, sprigs of the herb have been steeped in Rhenish white wine with sugar and strawberries to create a fragrant punch served on Walpurgis Night and May Day.

In the Middle Ages, it was known as an herbal medicine since the dried leaves contain coumarin and infusions were used as a spring tonic and even as an aphrodisiac. In Germany, the flowers are used to flavor young Riesling, called Maiwein (May Wine).

Household, Textile, and Craft Uses

Woodruff consists of purpurin, anthraquinone, and alizarin, which makes it appropriate for dyeing textiles, clothing, and paintings. Woodruff can be dried and stored in clothing, linens, and bedding in order to ward off insects and moths.

3. Key Constituents and Active Compounds

Primary Phytochemicals

The plant contains coumarin (0.4–1%), asperuloside (0.05–0.3%), monotropein (0.04%), tannins, iridoids, anthraquinones, flavonoids, and traces of nicotinic acid.

A 2025 comprehensive phytochemical analysis (published in Phytochemistry) identified thirteen isolated compounds in G. odoratum:

• Flavonoid glycosides: quercetin 3-O-[α-l-rhamnosyl-(1→6)-β-d-glucosyl]-7-O-β-D-glucoside and kaempferol 3-O-[α-l-rhamnosyl-(1→6)-β-d-glucosyl]-7-O-β-D-glucoside, which were for the first time isolated from G. odoratum.
• Iridoids and coumarin precursors: monotropein, geniposidic acid, scandoside, asperulosidic acid, deacetylasperuloside, and asperuloside, as well as 3-O-caffeoylquinic acid (neochlorogenic acid) and 5-O-caffeoylquinic acid (chlorogenic acid), which were already known from this species, were isolated from a methanolic extract of G. odoratum.
• Coumarin subtypes: the coumarins in this plant are of the unsubstituted coumarin, umbelliferone, and scopoletin types.
• Flavonoid glycosides: flavonoid glycosides like rutin have also been recognized in this plant.

The pharmacological potential is attributed to versatile nutraceuticals, mainly polyphenolic compounds such as coumarin, asperuloside, rutin, quercetin, monotropein, scandoside, and kaempferol, in addition to approximately 96 compounds in the essential oil, mainly thymol (30.6%) and isothymol (22.8%).

Coumarin: Formation, Stability, and Drying Dynamics

A 2025 study demonstrated for the first time that coumarin decreases during drying due to sublimation, which supports the use of fresh or minimally air-dried material in traditional recipes with specific drying times. This finding has direct implications for the preparation of herbal products and the interpretation of historical recipes that specify semi-wilted or briefly dried plant material.

Results revealed that while coumarin levels remain stable regardless of environmental conditions (sun-grown vs. shade-grown), phenolic content and antioxidant activity increase significantly under sun-grown conditions, with chlorogenic acid and rutin identified as major contributing compounds.

Mechanisms of Action

Chlorogenic acid and coumarin are well known for their potent antioxidant properties and are capable of neutralizing free radicals and reducing oxidative stress. Rutin, a flavonoid, is recognized for its ability to stabilize capillaries and reduce inflammation, whereas asperuloside has been associated with anti-inflammatory and immunomodulatory effects.

The synergistic action of these compounds may explain why G. odoratum extracts exhibit antioxidant activity and effectively reduce M1 macrophage polarization, thereby offering the potential for modulating inflammatory responses.

Tannins can accelerate wound healing through different mechanisms such as antioxidant, astringent, antibacterial, and angiogenic activity.

The broad pharmacological potential of G. odoratum is partly due to the high concentrations of coumarin, making it a commercially grown plant to produce coumarins, since this phytochemical has antitumor, bacteriostatic, antipsoriasis, cytotoxic, hepatoprotective, analgesic, antipyretic, and anti-cancerous reported activities. Moreover, coumarin has been used in the development of many therapeutic drugs used as anticoagulants.

Due to its antioxidant, neuroprotective, and anti-inflammatory properties, G. odoratum is recognized for antispasmodic, sedative, and anticoagulant effects and is used for digestive support.

4. Scientific Evidence by Area of Use

4.1 Anti-Inflammatory Activity

Preclinical (animal) evidence: In an in vivo evaluation of anti-inflammatory effect in rats, G. odoratum inhibited carrageenan-induced rat paw edema by 25%, which was favorably compared with the reference standard, indomethacin.

In vitro (cell) evidence: In a 2024 study published in the journal Antioxidants, the influence of sunlight exposure on the phytochemical composition and anti-inflammatory potential of G. odoratum extracts was assessed. The extracts from cultivated and wild-grown plants were analyzed via chromatographic and mass spectrometric methods, and the total phenolic content, antioxidant activity, and effects on macrophage polarization were assessed. The extracts exhibited anti-inflammatory activity, effectively reducing the M1 macrophage population involved in inflammatory responses.

A study on G. verum highlighted its ability to reduce proinflammatory cytokines such as IL-6 and CXCL8, emphasizing its potential as a therapeutic agent for managing inflammatory conditions. Similarly, G. odoratum was found to contain bioactive compounds that modulate immune responses by decreasing the production of proinflammatory cytokines, further supporting its application in inflammatory treatments.

Evidence strength: Preliminary. Evidence is restricted to animal and cell-based models. No human clinical trials on the anti-inflammatory effects of G. odoratum have been published.

4.2 Antioxidant Activity

Chlorogenic acid and coumarin are well known for their potent antioxidant properties and are capable of neutralizing free radicals and reducing oxidative stress.

Studies have investigated the protective effect of G. odoratum essential oil in reducing the damage of DNA caused by oxidation in cultured human lymphocytes. This represents one of the few studies involving human-derived cells, though it is ex vivo rather than a clinical trial.

Evidence strength: Preliminary; largely in vitro and ex vivo. No clinical antioxidant endpoint trials in humans have been reported.

4.3 Wound Healing and Burn Healing

Preclinical evidence: A study was conducted to evaluate the burn wound healing and antioxidant activity of methanolic and aqueous extracts of Galium odoratum in rats. Second degree burn wounds were induced in six groups of six rats each. Groups 1 and 2 received eucerin and silver sulfadiazine as control and reference standard, and groups 3, 4, 5, and 6 were given methanolic and aqueous extracts of 15% and 30% (w/w in eucerin base), respectively. The topical treatment was done daily for 14 days. The percentage of wound contraction and histology parameters of healed wounds were observed. There was statistically significant improvement in wound contraction of animals treated with extracts in comparison to control (p < 0.001). The healed wounds in extract-treated animals contained less inflammatory cells and had better re-epithelialization.

Evidence strength: Preclinical only (rat model). No human clinical wound healing trials have been reported for G. odoratum.

4.4 Antimicrobial and Antiviral Activity

The antimicrobial, antiviral, and antifungal activities of G. odoratum were documented; its ethanolic extract has an antimicrobial inhibition zone comparable to that of Gentamicin, mainly against Gram-positive bacteria.

An anthraquinone derivative in G. odoratum showed an inhibitory effect against thymidine kinase of herpes simplex virus 1 (HSV-1). Only a few studies showed some potential antiviral activity of plant extracts containing asperuloside. It has not yet been demonstrated that asperuloside alone can be used against viral infections.

Evidence strength: Weak; antimicrobial data are in vitro, and antiviral evidence is preliminary. No clinical infection trials have been conducted.

4.5 Sedative and Central Nervous System Effects

A proven effect is the locomotor activity-decreasing potential in a dose-dependent manner, giving this plant species a significant sedative effect acting on the central nervous system without affecting muscle tone and coordination. This effect was observed in preclinical (animal) models.

Evidence strength: Preclinical only. Traditional reports of sedative and calming effects in humans lack clinical verification.

4.6 Digestive Support

G. odoratum is used for urinary and stomach disorders and as a spasmolytic, expectorant, and against liver and bile diseases. These uses are based on traditional and ethnopharmacological records rather than controlled clinical trials. Sweet woodruff is reported to have anti-inflammatory and antibacterial activities, although the literature reveals no clinical data regarding the use of sweet woodruff for any condition.

Evidence strength: Traditional use only; no human clinical data.

4.7 Venous and Circulatory Disorders

Aerial parts and flowering tops are used as a treatment for nervous agitation, jaundice, hemorrhoids, circulation and venous disorders traditionally, and the crushed leaves have been used topically to reduce swelling and to accelerate wound healing.

Evidence strength: Traditional use only. The anticoagulant and circulatory effects attributed to the herb are likely related to its coumarin content, but direct clinical studies on G. odoratum for venous disorders are absent from the literature.

5. Body Systems and Health Areas of Association

• Hepatobiliary system: Traditionally used to treat digestive and bladder disorders, hepatitis, and nervousness.
• Nervous system: The leaves are described as antispasmodic, cardiac, diaphoretic, diuretic, and sedative. An infusion is used in the treatment of insomnia and nervous tension.
• Integumentary system (skin and wound healing): Sweet woodruff gained a reputation as an external application to wounds and cuts during the Middle Ages.
• Musculoskeletal and venous circulation: Traditionally used for varicose veins and hemorrhoids, attributable to rutin's capillary-stabilizing properties.
• Urinary system: In current use it is valued mainly for its tonic, diuretic, and anti-inflammatory effects.
• Immune and inflammatory: The extracts exhibited anti-inflammatory activity, effectively reducing the M1 macrophage population involved in inflammatory responses. The G. odoratum extracts contain compounds such as chlorogenic acid, coumarins, rutin, and asperuloside, which are likely responsible for the total phenolic content, antioxidant activity, and anti-inflammatory effects on M1 macrophages.

6. Dosage Forms and Reported Dosages

There is no proven safe or effective dose of sweet woodruff. Nonetheless, a tea of sweet woodruff made by pouring 3 cups of boiled water over herb (1 ounce of dry herb or 1½ ounces of fresh herb) and letting the tea steep for 10 minutes has been used traditionally.

Regarding safe limits for the coumarin content in beverages: studies suggest the safety limit for preparation of spiced wine is less than 5 ppm of coumarin, which corresponds to 3 to 3.5 g of fresh woodruff per liter of beverage.

In the animal burn-healing study, groups received methanolic and aqueous extracts of 15% and 30% (w/w in eucerin base) as topical preparations.

For the preparation of one liter of woodruff syrup, no more than approximately 20 grams of fresh woodruff leaves should be used, according to Austrian food safety guidance (AGES).

In general, preparations in clinical and ethnobotanical contexts include dried herb infusions/teas, alcoholic tinctures, and topical poultices. No standardized dosage for a dietary supplement product has been established in authoritative pharmacopeial monographs for G. odoratum at this time.

7. Safety Considerations and Known Interactions

Coumarin Content and Hepatotoxicity

The most important longer-range concern involves coumarin exposure and liver sensitivity. Modern toxicology reviews on natural coumarins note that the main adverse effect concern is hepatotoxicity in susceptible individuals or at excessive intake.

Based on available data, coumarin-induced hepatotoxicity is restricted to a small subset of patients, probably due to the activation in these individuals of alternative metabolic pathways involving specific CYP450 isoforms.

There is a large body of data on the toxicity of coumarin in experimental laboratory animals. Coumarins have hepatotoxic and carcinogenic properties in vivo in rodents and other mammalian species. These included adenomas and carcinomas of the liver, lungs, and bile ducts, and adenomas of the kidney and liver in rats and mice, respectively. Carcinomas were found only at doses higher than 100 mg/kg body weight per day.

In Australia, coumarin itself was authorized for the treatment of lymphedema in 1993, but in 1996 the Australian regulatory authorities suspended the drug due to the appearance of ten cases of hepatotoxicity with two fatalities.

Regulatory Status of Coumarin in Foods

Coumarin was banned as a food additive in the United States in 1954, largely because of the hepatotoxicity results in rodents. Coumarin is currently listed by the FDA among "Substances Generally Prohibited From Direct Addition or Use as Human Food" under 21 CFR 189.130, but some natural additives containing coumarin, such as the flavorant sweet woodruff, are allowed "in alcoholic beverages only" under 21 CFR 172.510.

Maximum levels for coumarin in foodstuffs are regulated in Annex III of the Flavourings Regulation 1334/2008 in the EU. Although the coumarin content in sweet woodruff or its plant parts is variable, coumarin is the substance identified as a concern by EFSA in its Compendium of Botanicals list.

Tolerable Daily Intake (TDI) for Coumarin

The German Federal Institute for Risk Assessment (BfR) and the European Food Safety Authority (EFSA) have calculated a tolerable daily intake (TDI) of 0.1 mg of coumarin per kg of body weight per day. This means that a person weighing 60 kg can consume 6 mg of coumarin per day for the rest of their life without fear of adverse effects.

Based on the analysis of cases of liver damage in humans and applying a safety factor of 5, the BfR set a coumarin dose of 5 mg/person/day that would exclude any possible risk of hepatotoxicity.

To avoid exceeding the TDI set by EFSA, the French Agency (ANSES) recommends keeping coumarin intake through food supplements below 4.8 mg per day for a 60 kg adult. ANSES also advises people with a history of liver disease to avoid consumption of coumarin-containing food supplements.

Anticoagulant Risk Distinction

The presence of dicoumarol in plants is relatively rare apart from molded sweet clover; therefore, the risk of an accidental anticoagulant effect with hemorrhage after ingesting dietary plants rich in coumarin (such as sweet woodruff) is considered low. The parent compound coumarin present in sweet woodruff is structurally distinct from the potent anticoagulant drugs derived from dicoumarol. Nevertheless, because coumarin derivatives are the basis of anticoagulant drug development, caution may be warranted in people taking anticoagulant medications, though direct interaction studies with G. odoratum in humans are absent from the published literature.

Pregnancy and Lactation

There is some concern over the toxic potential of the plant's coumarin content; therefore, use during pregnancy and lactation is to be avoided.

Topical Use

Although woodruff has traditional use on skin, coumarin-related compounds and plant sensitizers can still cause irritation.

Summary of Evidence Gap

Sweet woodruff is reported to have anti-inflammatory and antibacterial activities, although the literature reveals no clinical data regarding the use of sweet woodruff for any condition. All pharmacological data beyond its traditional record derive from in vitro cell studies and animal experiments. This represents a fundamental limitation: the absence of randomized controlled trials or systematic clinical reviews means that no therapeutic claim can be substantiated in humans at this time.

References

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• Kahkeshani et al. (2013). Antioxidant and burn healing potential of Galium odoratum extracts. Research in Pharmaceutical Sciences, 8(3), 197–203. PMC.
• Herre et al. (2025). Comprehensive analysis of natural products of Galium odoratum (Rubiaceae), focusing on the formation of coumarin during the drying process. Phytochemistry. PubMed.
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