Avens (Geum urbanum L.): A Comprehensive Reference
1. Identity: Botanical Classification, Names, and Natural Source
Geum urbanum, also known as wood avens, herb Bennet, colewort, clove root, and St. Benedict's herb (Latin: herba benedicta), is a perennial plant in the rose family (Rosaceae), which grows in shady places — such as woodland edges and near hedgerows — in the temperate regions of Eurasia and North America. The genus name Geum derives from the Greek geno, meaning "an agreeable fragrance," a reference to the characteristic scent of the freshly dug root. This gives rise to another common name, Radix caryophylata, or Clove Root, and its corruption, Gariophilata.
The accepted binomial is Geum urbanum L., where the species epithet urbanum means "city dweller," indicating this wild flower of hedges and woods was once found in urban areas. Common synonyms used historically in the pharmaceutical literature include Geum caryophyllata Gilib. and related subspecific names. Common vernacular names across Europe include benoîte (French), Stadtnelkenwurz (German), nejlikrot (Swedish), hierba de San Benito (Spanish), and kyläkellukka (Finnish).
Geum urbanum is a downy perennial herb with a short, thick rhizome and thin wiry stems, reaching up to 60 centimetres (24 in). The rhizome is purple in cross-section. Wood avens flowers in May or June with small yellow flowers appearing in cymes, which are typical of the Rose Family with five loose petals and five long sepals. The fruits tend to be more noticeable as brown burrs of seeds covered in small hooks.
The avens (Geum urbanum, Linn.), belonging to the order Rosaceae, is a common wayside plant in Great Britain, abundant in woods and hedges in England, Ireland, and southern Scotland, though becoming scarcer in the north. It is common in the greater part of Europe, Russia, and Central Asia.
A closely related species, water avens (Geum rivale), grows in damper and shadier habitats and is used for similar ailments. It is more bitter and less aromatic as it contains less eugenol in the root. Water avens also lacks the fever-reducing ability that wood avens holds.
Parts Used and Common Preparations
The root and leaves are the parts principally used medicinally. The principal constituents are yielded to water and alcohol. The roots of wood avens and water avens have been used as a substitute for clove because of their eugenol content, as an additive to spirits and liqueurs in the food industry, and as cosmetic ingredients in toothpastes and mouthwashes. Common preparation forms include:
- Infusion/Decoction: The roots and rhizomes decoction has been applied for the treatment of diarrhoea, dysentery, dyspepsia, and gastroenteritis, whereas the aerial parts infusion was used in cases of leucorrhoea, haemorrhages, and fever.
- Tincture: Alcoholic extracts prepared at various ratios (1:1 fluid extract or 1:10 tincture).
- Dried Powder: Methods of preparation include dry powder and non-standardized extracts such as dry extract, tincture, fluid extract, decoction, and infusion, typically using 1–12 grams of dried herb top and/or root per day.
- Topical poultice: Roots were traditionally applied externally in infusions or decoctions to reduce bleeding and inflammation of the gums, while poultices from the plant were used for wound healing and skin irritations.
2. Traditional and Historical Use
Medieval and Early Modern Europe
Geum urbanum has a long history of use in traditional European folk medicine primarily as an astringent agent to treat gastrointestinal issues such as diarrhea and indigestion, as well as oral conditions like gingivitis and mouth ulcers. Wood avens was a revered herb of medieval times, both for medicine and for protection against evil spirits.
The Anglo-Saxon "Herbal of Apuleius," a 10th-century translation and adaptation of the pseudo-Apuleian text from late antiquity, includes descriptions of the plant, recommending it for treating wounds and digestive ailments due to its astringent properties. The 12th-century mystic Hildegard von Bingen referenced it in her writings on natural medicine, calling it herba benedicta and praising its protective qualities against poisons and evil influences, often prescribing root infusions for stomach disorders and as a general tonic.
It was called "the Blessed Herb" (Herba benedicta), of which the common name "Herb Bennet" is a corruption, because in former times it was believed that it had the power to ward off evil spirits and venomous beasts. It was worn as an amulet. The Ortus Sanitatis, printed in 1491, states: "Where the root is in the house, Satan can do nothing and flies from it."
A cordial against the plague was made by boiling the roots in wine. English botanist John Gerard recommended a "decoction made in wine against stomach ills and bites of venomous beasts."
In medieval Europe, wood avens was commonly believed to have the power to ward off evil spirits, witches, and malevolent forces. People often wore the herb as an amulet or placed it in their homes to provide spiritual protection.
Traditional Medicinal Applications
Decoctions and infusions from aerial parts, roots, and rhizomes were recommended for the treatment of diarrhea, dysentery, dyspepsia, gastroenteritis, leucorrhoea, haemorrhages, infections, and fever. The infusion was also ingested against rheumatism, gout, infections, and fever.
Preparations derived from roots and rhizomes of Geum urbanum L. are traditionally used for the treatment of ulcers and irritations of mucous membranes of the mouth, stomach, and intestinal tract. Geum urbanum L. root infusions and decoctions have been used externally for reducing the bleeding and inflammation of gums (gingivitis) and mucous membranes.
Historically, the plant featured in plague remedies, valued for its antiseptic properties and incorporated into cordials for protection against infections.
By the 19th century, Geum urbanum received systematic documentation in botanical floras as part of European natural history surveys. Wood avens has been used from ancient times as a medicinal plant but is only rarely applied in modern phytotherapy.
3. Key Constituents and Active Compounds
More than 200 compounds — monoterpenoids, sesquiterpenes, triterpenoids, flavonoids, hydrolysable tannins, and phenylpropanoids — have been isolated from the genus Geum since 1920.
Phenolic Acids and Polyphenols
Geum urbanum contains phenolic compounds including gallic, caffeic, and chlorogenic acids, as well as eugenol, vicianose sugar, carotenoids, flavonoids, tannins (approximately 10.5%), volatile oil, and the sesquiterpene lactone cnicin. From the roots, the rare disaccharide vicianose, the phenylpropanoid gein, catechin, gallic acid, galloylglucose, caffeic acid, chlorogenic acid, and ellagic acid have been identified.
Tannins
The main secondary metabolites of the roots and herbal parts reported so far are gallo- and ellagitannins, procyanidins and other polyphenolics, ascorbic acid, and essential oil components, such as eugenol. The high tannin content is typical for the Rosaceae family. Six ellagitannins have been isolated from the roots of Geum urbanum, including gemin A, pedunculagin, stachyurin, stenophyllanin A, casuarinin, and gemin G.
Constituents include tannins (approximately 15%), essential oils including eugenol, bitter principles, resin, organic acids, and sugars. Polish research in 2013 showed eugenol making up 65–75% of the essential oil in the herb.
Essential Oil: Eugenol and Related Compounds
The essential oil from the root is dominated by eugenol (69.2%), followed by cis-myrtanal (15.3%), and related compounds with a pinane skeleton: trans-myrtanol (3.2%), myrtenal (3.0%), trans-myrtanal (2.9%), and myrtenol (2.1%). These six compounds account for 95.7% of the oil.
The main compound of the essential oil from the underground parts of G. urbanum was eugenol (69.2%), whereas the essential oils from aerial parts of the plant contained large amounts of aliphatic compounds with (Z)-3-hexenol (38.4%) being the dominant constituent of the essential oil from aerial parts of G. urbanum.
Flavonoids
Leaves are notable for flavonoids, which support antioxidant and anti-inflammatory activities. For both Geum species, phenolic compounds such as flavonoids and gallic acid derivatives, and triterpenes such as saponins and their aglycones, have been detected. Both Geum species have also revealed the presence of derivatives of the triterpenoid aglycones asiatic acid and madecassic acid, which were characterized for the first time in the genus Geum.
Quercetin and kaempferol derivatives are present and provide antioxidant support by scavenging free radicals.
Established Mechanisms of Action
Two major groups of constituents appear to be responsible for medicinal activities in Geum: phenylpropanoids, especially eugenol, and tannins, present in high concentrations.
- Tannins (astringent/anti-inflammatory mechanism): Gallotannins and ellagitannins (e.g., pedunculagin) deliver astringent effects — precipitating proteins to reduce secretions, soothe mucous membranes, and tighten tissues.
- Gemin A (anti-inflammatory at the cellular level): The ellagitannin gemin A significantly affected the functions of stimulated neutrophils by reducing the surface expression of CD11b and inhibiting the release of reactive oxygen species and proteases (elastase, MMP-9), chemokines, and cytokines (interleukins IL-8, IL-1β).
- Eugenol (local anesthetic / antiseptic): Eugenol, the characteristic clove-scented constituent, offers local anesthetic and antiseptic actions by modulating pain receptors and disrupting bacterial cell membranes.
- Antibacterial activity of tannins: Antibacterial activity of Geum extracts is not primarily attributed to their essential oil components; eugenol, as a single substance, showed only minor effects on the germs investigated. Furthermore, antibacterial activity of G. rivale, which contains only low amounts of eugenol, was comparable to that of G. urbanum. Thus, antibacterial effects of the extracts are probably due to tanning compounds found in both species in considerable amounts.
- High-molecular tannins most active: The antibacterial activity of various extracts of fresh and dried G. urbanum roots and rhizomes was assessed against Staphylococcus aureus and Cutibacterium acnes. Fractionation of low- and high-molecular tannins by column chromatography demonstrated the latter to exhibit the highest antibacterial activity.
4. Scientific Evidence by Area of Use
4.1 Gastrointestinal Health
Geum urbanum has historically been used for diarrhea, dyspepsia, and intestinal inflammation, with the tannin content providing a plausible mechanistic basis. Roots and rhizomes are traditionally applied to treat stomach complaints as a tea against ulcers and irritations of mucous membranes of the mouth and intestinal tract. G. urbanum plants, especially their roots, are rich in tannins — a characteristic of many species of the Rosaceae family — and have been applied together with the closely related Geum rivale for the treatment of diarrhea, digestive disorders, and hemorrhoids, mainly due to the occurrence of astringent, antiseptic, and antimicrobial gallo- and ellagitannins.
Evidence strength: The evidence for gastrointestinal uses rests principally on traditional and ethnopharmacological data, supported by the known chemistry of tannins (protein-precipitating, mucosa-tightening effects), but no controlled clinical trials in human populations have been published. The mechanistic rationale is plausible, but evidence is pre-clinical and traditional.
4.2 Oral Health: Gingivitis, Periodontitis, and Mucositis
One of the better-investigated areas concerns oral inflammation. In order to confirm the purposefulness of the traditional topical use of Geum urbanum root preparation in gum inflammation, researchers investigated the effects of phytochemically characterized (HPLC-DAD-MSn) extracts of different polarity on oxidative burst, on elastase, metalloproteinase 9 (MMP-9), interleukin 8 (IL-8) and 1β (IL-1β), tumour necrosis factor (TNF-α) release, expression of adhesion molecules (CD62L and CD11b), and delayed apoptosis in formyl-methionyl-phenylalanine (f-MLP)/cytochalasin A (CA) or lipopolysaccharide (LPS)-stimulated neutrophils.
The modulating effect on the functions of neutrophils of the extracts, and of its main constituent gemin A, supports the traditional use of this plant material in cavity inflammation including mucositis, gingivitis, and periodontosis.
A study supported the traditional use of Geum urbanum L. root, which contains ellagic acid derivatives, in cavity inflammation including mucositis, gingivitis, and periodontal disease.
Evidence strength: Current evidence is in vitro and ex vivo (stimulated human neutrophils). These studies provide mechanistic support for traditional topical oral use but do not constitute controlled clinical evidence. No published randomized controlled trials in human patients with gingivitis or periodontitis using standardized Geum urbanum preparations have been located.
4.3 Antimicrobial Activity
Ethnopharmacological data suggest antimicrobial and radical scavenging properties of the extracts. In laboratory investigations, the methanol extracts of the roots and aerial parts of G. urbanum and their fractions were investigated for antibacterial and radical scavenging activity, revealing that G. urbanum L. is a prospective medicinal plant deserving further, more detailed studies.
A 2022 study published in Chemistry & Biodiversity (Bunse et al.) characterized secondary metabolites and evaluated the antimicrobial potential of different root and rhizome extracts. Among the findings, rare ellagitannin-sulfates were characterized by LC/MSn. The antibacterial activity of various extracts of fresh and dried G. urbanum roots and rhizomes against Staphylococcus aureus and Cutibacterium acnes was assessed and compared to that of G. rivale. Low- and high-molecular tannins were fractionated, demonstrating the latter to exhibit the highest antibacterial activity.
A separate PMC-published study evaluated resistance to MRSA, reporting that antimicrobial activity against Gram-positive bacteria of ethyl acetate extracts of roots and aerial parts was proven, with the aerial parts extract showing a minimal inhibitory concentration (MIC) of 39 µg/mL and the roots extract showing 313 µg/mL against MRSA. The EtOAcAP extract was proven to be an effective antistaphylococcal agent with favorable skin tolerance, showing strong antineoplastic activity and antibiofilm effect at sub-MICs, outlining new prospects for its development as a natural product for specific skin applications.
Evidence strength: All antimicrobial evidence is in vitro. No clinical trials in humans have assessed G. urbanum preparations for infectious conditions. Results are preliminary and require confirmation in animal and human studies.
4.4 Antioxidant Activity
More recent studies, especially on G. urbanum, have reported anti-inflammatory, antimicrobial, antioxidant, neuroprotective, and hypotensive effects. Antioxidant activity has been measured using established assays (DPPH, ABTS, FRAP). Geum urbanum rhizome extract showed high antioxidant activity in comparative assessments. The polyphenolic content — gallic acid, ellagic acid, quercetin derivatives, and procyanidins — provides a credible mechanistic basis.
Evidence strength: Antioxidant properties are well-supported at the in vitro level and are consistent with the phytochemical profile. No human clinical trials on antioxidant endpoints have been published.
4.5 Neuroprotective Activity and Parkinson's Disease Research
An ethanolic extract of Geum urbanum was investigated for its ability to inhibit α-Synuclein fibrillation, a process central to the pathology of Parkinson's disease. The aim was to investigate the inhibitory activity of an ethanolic extract of Geum urbanum against α-Synuclein fibrillation and to examine the structural changes of α-Synuclein in the presence of the extract. Lewy bodies and Lewy neurites primarily consist of fibrillated α-Synuclein. The anti-fibrillation and anti-aggregation activities of the plant extract were monitored by thioflavin T fibrillation assays and size exclusion chromatography, while structural changes were followed by circular dichroism, Fourier transform infrared spectroscopy, intrinsic fluorescence, small angle X-ray scattering, and electron microscopy.
Studies revealed that Geum urbanum (GU) extracts not only stabilize α-Syn fibrils but also promote their disaggregation in a concentration-dependent manner. At a high concentration (0.25 mg/mL), the extracts inhibited fibril formation for up to 40 hours, with the lag phase of fibrillation increasing proportionally with extract concentration.
The in vitro neuroprotective activity of G. urbanum extracts was also investigated via inhibition of acetylcholinesterase (AChE) and tyrosinase. AChE inhibitory activities of Geum urbanum aqueous extract were 27.03±1.5%, 36.48±1.7%, and 79.11±3.9% at concentrations of 0.75 mg/mL, 1.5 mg/mL, and 3 mg/mL respectively, with an IC50 of 2.293±0.14 mg/mL, while AChE inhibitory activities of Geum urbanum ethanol extract were 54.74±2.7%, 73.53±5.1%, and 86.77±5.1%, with an IC50 of 0.513±0.03 mg/mL.
Geum urbanum, a European traditional medicinal plant, is used against tremor, a symptom of Parkinson's disease. Ethanolic extraction of Geum urbanum has shown anti-amyloidogenic activity against α-Syn.
Evidence strength: Entirely in vitro. These findings are intriguing and provide a rationale for further investigation, but no animal model studies or human clinical trials relating to Parkinson's disease or cognitive function have been conducted with this plant.
4.6 Antineoplastic (Anti-Cancer) Activity
A study evaluated the in vitro antineoplastic and antiviral potential and in vivo toxicity of twelve extracts with different polarity obtained from Geum urbanum L. In vitro cytotoxicity was determined by ISO 10993-5/2009 on bladder cancer (T-24 and BC-3C), liver carcinoma (HEP-G2), and normal embryonic kidney (HEK-293) cell lines. Antineoplastic activity was elucidated through assays of cell clonogenicity, apoptosis induction, nuclear factor kappa B p65 (NFκB p65) activation, and total glutathione levels.
The ethyl acetate extract of aerial parts (EtOAc-AP) exhibited the strongest antineoplastic activity on bladder cancer cell lines (IC50 = 21.33–25.28 µg/mL) by inducing apoptosis and inhibiting NFκB p65 and cell clonogenicity. EtOAc and n-butanol extracts showed moderate antiviral activity against human adenovirus type 5 and human simplex virus type I. Seventy-four secondary metabolites (gallic and ellagic acid derivatives, phenolic acids, flavonoids, etc.) were identified in EtOAc-AP by UHPLC–HRMS.
The ethyl acetate extract of aerial parts (EtOAc-AP) exhibited the strongest antineoplastic activity on bladder cancer cell lines by inducing apoptosis and inhibiting NFκB p65 and cell clonogenicity, thus helping the development of health-promoting phytopreparations.
Evidence strength: Exclusively in vitro and early-stage. These findings are preliminary and do not establish clinical efficacy. No human oncology trials exist.
4.7 Hypotensive and Cardiovascular Activity
Geum urbanum has been documented to possess anti-inflammatory, antimicrobial, antioxidant, neuroprotective, hypotensive, and other pharmacological effects in laboratory settings. The hypotensive (blood-pressure lowering) effects documented in the literature are derived from in vitro and animal-model research. Geum urbanum also exhibits cardioprotective properties in experimental contexts.
Evidence strength: Pre-clinical only. No human trials on blood pressure outcomes have been reported.
4.8 Anti-Diabetic Activity
A 2021 study published in Frontiers in Pharmacology (Günther et al., PMC-indexed) investigated an avens root extract discovered by target-based screening, finding it to exhibit antidiabetic activity in the hen's egg test model and in Drosophila melanogaster, two pre-clinical model systems. This work is in its very early stages and no human trial data exist.
Evidence strength: Very preliminary, animal/invertebrate model only. Clinical relevance is entirely unknown.
5. Body Systems and Health Areas Associated with Avens
- Gastrointestinal system: Diarrhea, dyspepsia, dysentery, gastroenteritis, gastric ulcers, irritable gut mucosa, hemorrhoids
- Oral cavity: Gingivitis, mucositis, periodontitis, bleeding gums, mouth ulcers
- Immune and inflammatory: Anti-inflammatory (neutrophil modulation, NF-κB inhibition in vitro), fever
- Antimicrobial: Gram-positive bacteria (including MRSA, S. aureus, C. acnes), antifungal (historical)
- Neurological: α-Synuclein aggregation inhibition, acetylcholinesterase inhibition (in vitro), historical use for tremor
- Cardiovascular: Cardioprotective and hypotensive effects in pre-clinical models
- Dermatological: Wound healing, skin irritations (topical use); antistaphylococcal skin applications
- Systemic antioxidant: Radical scavenging activity across multiple in vitro assays
- Metabolic/endocrine: Antidiabetic activity in preliminary pre-clinical models
6. Dosage Forms and Dosages Reported in Sources
No standardized clinical dosage has been established through controlled trials. The following dosages are those reported in reference sources and traditional herbalism literature:
- Dried root/herb (general): 1–12 grams of dried herb top and/or root per day, as reported in Wichtl (2004), the British Herbal Pharmacopoeia (BHP 1983), and Grieve (1971).
- Root infusion/tea: 2 g dried root per 300 mL water, taken twice daily.
- Tincture: 2–5 mL, three times daily between meals.
- Fluid extract (1:1): 20–40 drops, one to three times a day.
- Tincture (1:10): 50–100 drops, one to three times a day, before meals.
- Powder: 1–4 g per day, in three divided doses.
- Topical: Fresh plant, crushed, applied in the form of poultices.
No standardized extract forms (e.g., specific ratios of ellagitannins or eugenol) have been established for commercial or clinical use based on published clinical trial data, as no such trials exist.
7. Safety, Adverse Effects, and Drug Interactions
Acute Toxicity
An ethyl acetate extract of aerial parts of Geum urbanum induced no signs of acute toxicity in liver and kidney specimens of H-albino mice in doses up to 210 mg/kg. This suggests a reasonable safety margin for the extract at tested concentrations in this pre-clinical model, though direct extrapolation to human dosing is not established.
Gastrointestinal Adverse Effects
Overuse (e.g., greater than 4 g/day of powder) may cause nausea or constipation via excess tannins. The high tannin content, which is the principal pharmacologically active component, is also the basis for the most likely adverse effect at higher doses.
Allergic and Hypersensitivity Reactions
Rare contact dermatitis from eugenol has been reported; a patch test before topical use is advisable. Eugenol is a known allergen in dental products and some cosmetics; individuals sensitized to eugenol or related clove-containing preparations are at elevated risk.
Salicylate sensitivity may trigger asthma or hives in sensitive individuals, due to low levels of salicylic acid present in the plant.
Drug Interactions
Blood thinners such as warfarin could have a potentiated anticoagulant effect when used concurrently; INR monitoring has been suggested if used together. This interaction has not been documented in controlled clinical studies and represents a theoretical concern based on the phytochemistry rather than confirmed case reports.
High tannin content in the preparation may interfere with the absorption of certain medications — particularly iron salts, alkaloid-based drugs, and some antibiotics — when taken concurrently, a well-established pharmacokinetic interaction class for tannin-rich botanicals, though no specific interaction studies involving G. urbanum preparations have been published.
Pregnancy and Lactation
There are no robust clinical data regarding use during pregnancy and breastfeeding; avoidance or minimal use under professional guidance is generally recommended. Regulatory guidance (Health Canada) advises consulting a healthcare practitioner prior to use if pregnant or breastfeeding.
Regulatory Status and Formal Monograph Coverage
Geum urbanum is listed as a natural health product ingredient by Health Canada, with permitted forms including dry, powder, and non-standardized extracts such as tinctures, fluid extracts, decoctions, and infusions. Health Canada lists no mandatory contraindications or known adverse reactions in its monograph for standard use. No published EMA (European Medicines Agency) Community Herbal Monograph for Geum urbanum has been located in the open literature, and the German Commission E did not produce an approved monograph for this plant. The plant is listed in the VOLKSMED database as a traditional Austrian herb: the species is listed in the VOLKSMED database as a traditional Austrian herb with anti-inflammatory activity.
Overall Evidence Summary
The scientific literature on Geum urbanum remains largely pre-clinical. Herbalists use wood avens to treat various diseases, but there is no evidence from clinical trials that it makes any difference to patient outcomes. The body of in vitro and mechanistic work is growing, particularly around oral inflammation (gingivitis/periodontitis), antimicrobial activity, and neuroprotection via α-Synuclein inhibition, and some of this work does provide biologically plausible support for traditional uses. However, no randomized controlled clinical trials in humans have been published for any indication as of the most recent searches. Evidence for all uses must therefore be characterized as preliminary, traditional, or mechanistically suggestive rather than clinically proven.
References
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