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Alder Buckthorn / Glossy Buckthorn (Frangula alnus; syn. Rhamnus frangula)
Materia Medica
Family: Rhamnaceae
Accepted name: Frangula alnus Mill.
Important synonym: Rhamnus frangula L.
Common names: Alder Buckthorn, Glossy Buckthorn, Frangula
Medicinal part: Dried bark of stems and branches — Frangulae cortex
Growth habit: Deciduous shrub or small tree
Native range: Europe to Central Siberia and Xinjiang, plus northwestern Africa
Primary medicinal role: Short-term stimulant laxative for occasional constipation
Actions & Energetics
Frangula bark is a stimulant laxative. Its medicinal action is attributed mainly to hydroxyanthracene derivatives standardized as glucofrangulin A equivalents.
- Primary action: Stimulates colonic motility and alters water/electrolyte transport in the large intestine
- Modern indication: Short-term treatment of occasional constipation
- Use pattern: Intermittent, short-term use rather than daily long-term bowel support
- Evidence level: EMA well-established use based on bibliographic evidence, clinical experience, and anthranoid-laxative data; recent single-ingredient trials are limited
Botanical Description
Frangula alnus is a deciduous shrub or small tree. Young bark is relatively smooth and gray-brown to dark brown, often with conspicuous pale horizontal lenticels. Unlike common buckthorn (Rhamnus cathartica), glossy buckthorn does not typically end its twigs in a true terminal thorn.
Leaves are alternate, oval to obovate, generally smooth-edged, and characteristically glossy above. Their lateral veins curve upward toward the leaf margin. Small greenish-white flowers occur in clusters from the leaf axils. Fruits ripen through green and red stages to dark purple-black.
Name Confusion & Look-Alikes
Alder buckthorn is not an alder. Frangula alnus belongs to the Rhamnaceae, while true alders such as black alder (Alnus glutinosa) belong to the Betulaceae.
It should also be distinguished from common buckthorn (Rhamnus cathartica), another invasive buckthorn in Illinois. The older medicinal name Rhamnus frangula is a synonym of Frangula alnus, not a reference to common buckthorn.
Traditional Indications
Frangula bark has a long European history as a stimulant laxative. Modern EMA guidance narrows that traditional use to short-term occasional constipation.
The berries are not the standard medicinal drug and should not be substituted for properly prepared bark.
Preparations & Dosage
Standardized Bark Preparations
The current EMA monograph doses frangula preparations by their hydroxyanthracene content rather than by a fixed household spoonful of bark. For adolescents over 12, adults, and older adults, the single dose is a preparation equivalent to 10–30 mg hydroxyanthracene derivatives, calculated as glucofrangulin A, once daily at night.
The correct individual dose is the smallest amount needed to produce a comfortable, soft-formed stool.
Herbal Tea
EMA permits an infusion prepared from an amount of comminuted bark providing no more than 30 mg hydroxyanthracene derivatives in 150 mL boiling water. Because wild bark varies in active constituents, this should not be converted into an improvised gram dose unless the material has been properly standardized.
Frequency & Duration
Do not use for more than one week. EMA notes that it is usually sufficient to take the medicine only two or three times during that week.
Fresh Bark
The EMA monograph concerns dried, comminuted bark and standardized preparations. Freshly stripped bark is not equivalent to the pharmacopoeial medicinal material and should not be used as a home laxative.
Children & Adolescents
Use in children under 12 years is contraindicated. The EMA dose range applies to adolescents over 12, adults, and elderly patients.
Classical Formulations
Frangula bark has historically appeared in compound laxative formulas, but the current EMA monograph specifically evaluates frangula bark preparations rather than establishing one universal classical compound formula. Combination products require their own formulation-specific assessment.
Constituents
The medicinal bark contains hydroxyanthracene derivatives, especially glucofrangulin A and B, together with frangulins and emodin-related anthranoid compounds.
These constituents are responsible for the stimulant-laxative action and are also why medicinal products are standardized rather than dosed simply by appearance or a random quantity of wild bark.
Modern Research
Mechanism & Constipation
Hydroxyanthracene derivatives are converted in the colon to active metabolites. They increase large-intestinal motility and influence water and electrolyte movement, shortening transit time and increasing fluid in the bowel.
EMA classifies frangula bark as having well-established use for occasional constipation, but notes that recent studies of frangula bark alone are lacking. The conclusion also draws on long clinical experience and evidence from related anthranoid laxatives such as senna.
Hydroxyanthracene Safety Research
Hydroxyanthracene-containing laxatives have been the subject of modern genotoxicity and long-term-safety reviews. These concerns support limiting exposure to the smallest effective amount for the shortest necessary period rather than casual chronic use.
This does not mean that one properly used short course of a standardized frangula medicine is proven to cause cancer. It means chronic or unnecessary exposure is not appropriate.
Adverse Effects
Possible effects include abdominal pain, cramping, spasm, and liquid stools, particularly with excessive dosing or in people with an irritable colon.
Long-term stimulant-laxative use can cause water and electrolyte imbalance. EMA also notes possible albuminuria, haematuria, and reversible pseudomelanosis coli with prolonged use. Yellow to red-brown urine discoloration may occur from metabolites and is generally harmless.
Interactions & Contraindications
Frangula bark must not be used with intestinal obstruction or stenosis, intestinal atony, appendicitis, inflammatory bowel disease such as Crohn’s disease or ulcerative colitis, abdominal pain of unknown cause, or severe dehydration with water and electrolyte depletion.
Chronic laxative-induced potassium loss can increase risk with medicines sensitive to low potassium, including cardiac glycosides such as digoxin and certain antiarrhythmic drugs. Extra caution is warranted with other medicines that promote potassium loss, including some diuretics and corticosteroids.
Pregnancy & Breastfeeding
EMA contraindicates frangula bark medicines during pregnancy and breastfeeding. This is separate from ordinary dietary fiber and reflects the stimulant-laxative pharmacology and limited reproductive-safety basis for medicinal use.
Illinois Legal Status
Glossy buckthorn (Frangula alnus) is currently listed as an exotic weed under Illinois administrative rules. The Illinois rules require a Department of Natural Resources permit for buying, selling, offering for sale, distributing, or planting listed exotic-weed seeds, plants, or plant parts unless a specific exemption applies.
Illinois law also provides penalties for violations and allows exotic weeds offered for sale contrary to the Act to be confiscated and destroyed. For a business handling dried glossy-buckthorn bark, the important point is that the rule expressly includes plant parts; medicinal use does not automatically remove the material from the exotic-weed law.
This section describes the current Illinois rule and is not legal advice. Commercial handling should be checked against the current Illinois Department of Natural Resources permit and exemption requirements.
Habitat & Cultivation
- Native range: Europe to Central Siberia and Xinjiang; northwestern Africa
- Introduced range: Widely naturalized in parts of North America, including Illinois
- Growth habit: Shrub or small tree
- Habitat: Moist woods, wetlands, fens, bog margins, forest edges, and disturbed ground
- Ecology: Can form dense stands that suppress native vegetation
Because glossy buckthorn is legally listed as an exotic weed in Illinois, cultivation or intentional propagation there is not an appropriate herbal-garden recommendation without the required authorization.
Propagation
Biologically, the species reproduces readily by seed and can resprout after cutting. Birds and other wildlife disperse the fruits. In Illinois, do not propagate or plant glossy buckthorn unless legally authorized under the applicable exotic-weed rules.
Harvesting & Drying
The medicinal drug is the dried bark of stems and branches. A random piece of freshly stripped bark should not be treated as equivalent to standardized medicinal frangula bark.
In Illinois, harvesting, possessing for commercial distribution, selling, or otherwise handling material from this listed exotic weed can raise permit questions because the law covers plant parts. Legal status should be checked before commercial collection or distribution.
Food Use
Glossy-buckthorn fruit is not a routine human food and is not the recognized medicinal part. Wildlife consumption does not establish human food safety. Frangula bark is a pharmacologically active laxative drug material, not a culinary ingredient.
History, Folklore & Spiritual Use
Frangula bark has a long place in European laxative practice. The older botanical name Rhamnus frangula remains common in pharmacopoeias and medicinal literature even though current taxonomy accepts Frangula alnus.
In North America, the species’ history is very different: it escaped cultivation and became a serious invasive shrub in wetlands and other natural communities. Modern materia medica therefore has to consider both pharmacology and local ecological law.
Materia Medica Summary
Alder Buckthorn / Glossy Buckthorn (Frangula alnus; syn. Rhamnus frangula) is a Rhamnaceae shrub or small tree whose dried bark is a recognized stimulant laxative for short-term occasional constipation.
EMA dosing is standardized to 10–30 mg hydroxyanthracene derivatives calculated as glucofrangulin A, taken once daily at night, for no more than one week and usually only two or three times within that week. Use is contraindicated under age 12 and during pregnancy or breastfeeding. Long-term use risks fluid and electrolyte disturbances. In Illinois, glossy buckthorn is a listed exotic weed, and state rules restrict buying, selling, distribution, and planting of the plant and its parts without the required permit or applicable exemption.