IngredientsAlnus rubra Bong. — the red alder — is a deciduous broadleaf tree native to western North America, occurring naturally across Alaska, Yukon, British Columbia, Washington, Oregon, California, Idaho, and Montana. It belongs to the birch family (Betulaceae) and is also commonly known as the Oregon alder. Additional vernacular names documented in the literature include Amerikaanse rode els, aliso Americano, aune d'Oregon, ontano dell'Oregon, Pacific Coast alder, and western alder.
The species epithet rubra means "red," referring both to the red dye produced from the bark and to the color the wood acquires when cut. The name of the tree more broadly derives from the rusty red color that appears when its wood is cut or bruised.
Red alder is the largest species of alder in North America and one of the largest in the world, reaching heights of 20 to 30 metres (66 to 98 ft). The bark is mottled, ashy-gray, and smooth, often colonized by white lichen and moss; the leaves are ovate, 7 to 15 centimetres long, with bluntly serrated edges and a distinct revolute margin — a diagnostic character which distinguishes it from all other alders. The roots bear numerous nitrogen-fixing nodules, which represent a symbiotic association between the tree and beneficial bacteria of the genus Frankia.
The range of red alder extends along the Pacific coast from southern California (latitude 34°N) to southeastern Alaska (60°N), with the species not commonly found east of the Cascade or Sierra Nevada Ranges, although there are isolated populations in northern Idaho.
Red alder bark, root, and leaf extract have a long history of use in traditional medicine and hygiene. The bark is most commonly used medicinally, but the leaf buds, mature leaves, male catkins, and female green catkins are also considered medicinally relevant. Native American tribes from Alaska to Southern California used the bark layers, roots, leaves, twigs, cones, and sap for a variety of purposes; the inner bark was often dried, ground into a powder, and then used as a thickener in soups or mixed with cereals when making bread.
Preparations documented in the ethnobotanical and scientific literature include:
Red alder has highly desirable medicinal properties which have been capitalized on for thousands of years, including by Pacific West Coast Native Americans. Red alder was widely employed medicinally by Native North American Indians, who mainly used the bark to treat a wide range of complaints.
Ethnobotanically, Native Americans used red alder bark in traditional medicine for headaches, congestion, colds, anemia, pain relief (salicin being similar to aspirin), rheumatic pains, internal injuries, and diarrhea; bark poultices also relieved swelling, eczema, sores, and aches.
The Blackfoot Confederacy used an infusion made from the bark of red alder to treat lymphatic disorders and tuberculosis. Red alder was more broadly used by various Native groups to treat poison oak, insect bites, and skin irritations.
The Salinan used an extract of the bark of alder trees to treat cholera, stomach cramps, and stomachaches. Bark infusions were taken as a laxative and to regulate menstruation; the Pomo boiled the bark in water to make a wash to treat skin irritations and sores. Chewing the bark was employed to heal sores and ulcers in the mouth.
Among the Tanaina (Anchorage-area Natives), the inner bark was boiled and the tea was drunk to dispel gas in the stomach and to lower a high fever; the astringent and powerfully bitter bark infusion was also used as a gargle for sore throat, to induce circulation, to check diarrhea, and as eye drops.
The bark of red alder was used by coastal and western North American Indians to relieve indigestion and as a tonic and alterative.
Various layers of the red alder bark yield red, red-brown, brown, orange, and yellow dyes; these were used to color baskets, hides, moccasins, quills, and hair, and Native Americans of the Pacific Northwest extracted a red dye from the inner bark to dye fishnets. The wood of red alder was second only to cedar in its use for woodworking by coastal Native peoples; dishes, spoons, platters, masks, and many other items were crafted from it, and alder wood is considered the best wood for smoking salmon.
The plant is little used in modern herbalism, and there are no established pharmacopeial monographs (such as those of the German Commission E, ESCOP, or WHO) specifically for Alnus rubra as a medicinal species. Current scientific interest is largely concentrated in the laboratory isolation and characterization of its constituent compounds, particularly diarylheptanoids, as detailed below.
Red alder's desirable properties are largely attributed to its bioactive plant phenol metabolites, which include plant defense compounds, bark colorants, and various medicinally relevant substances. Diarylheptanoids are a group of secondary metabolites widely distributed in the Betulaceae family and characteristic of Alnus species.
Diarylheptanoids — especially oregonin ((5S)-1,7-bis(3,4-dihydroxyphenyl)-5-(β-D-xylopyranosyloxy)-heptan-3-one) — have been identified as major bioactive constituents of red alder. Previous chemical investigations have led to the isolation of triterpenoids, the diarylheptanoid xyloside oregonin, and a procyanidin polymer from Alnus rubra.
The full range of diarylheptanoid compounds documented across closely related alder species and in Alnus rubra-specific studies includes, but is not limited to: hirsutanonol, oregonin, lupenone, taraxerone, taraxeryl acetate, taraxerol, betulin, rubranoside A, rubranoside B, rubranoside C, platyphylloside, pectolinaringenin, lupeol, β-sitosterol, and apigenin.
Diarylheptanoids have been identified as the predominant compounds in alder bark extracts, with oregonin alone constituting 74.67% of total extract content in analyses of closely related Alnus glutinosa.
The bark contains salicin, which probably decomposes into salicylic acid (closely related to aspirin) in the human body; this has historically been considered the basis of its anodyne and febrifuge effects. This phenolic glycoside is shared with other members of the Betulaceae family and with willows (Salix spp.), whose bark has a well-established history of use for pain and fever.
The isolated pentacyclic triterpenes from Alnus species range from oleananes, ursanes, lupanes, and hopanes to fernanes. Among those specifically documented in red alder (Alnus rubra / Alnus oregona):
The genus Alnus is known to contain both condensed tannins (procyanidins/proanthocyanidins) and hydrolysable tannins, as well as flavonoids such as acacetin and apigenin. Reports testify that extracts and isolated compounds from different Alnus species have significant antimicrobial, immunomodulatory, antioxidant, and anti-inflammatory activity. The tannin content of the bark contributes directly to its well-documented astringency.
β-Sitosterol, also present in Alnus bark extracts, can reduce cholesterol, act as an anti-diabetic and cough expectorant, inhibit tumors, and assist tissue repair.
Studies examining oregonin and hirsutanonol isolated from alder bark found these compounds to be potent inhibitors of inducible nitric oxide synthase (iNOS); they showed inhibition of nitric oxide synthesis in dose-dependent manners by murine macrophage-like RAW 264.7 cells stimulated with interferon-gamma plus lipopolysaccharide, with IC50 values of 3.8 and 14.3 μM, respectively; the inhibitory effects were due to suppression of iNOS mRNA expression.
Structurally, hirsutenone, hirsutanonol, oregonin, rubranoside B, and rubranoside C — which possess two 3,4-dihydroxyphenyl rings — were more active against reactive oxygen species (ROS) than other diarylheptanoids with different ring substitution patterns. The scavenging capacity against peroxyl radicals is closely related to the number and arrangement of phenolic hydroxyls, which are essential to the higher antioxidative activity of diarylheptanoids.
Alder extracts acted early in the adipocyte differentiation process and acted as partial agonists toward peroxisome proliferator activated receptor gamma (PPAR-γ) activity; the diarylheptanoid glycoside oregonin was isolated and confirmed to be the active principle exerting the anti-adipogenic effect. This mechanism — partial PPAR-γ modulation — is relevant to the regulation of fat cell formation and differentiation, connecting alder constituents to metabolic research.
The bark contains salicin, which probably decomposes into salicylic acid (closely related to aspirin) in the human body, and this is the basis of its anodyne and febrifuge effects.
The scavenging capacity against peroxyl radicals is closely related to phenolic hydroxyls, and combined theoretical and experimental studies have confirmed that the catechol moiety, acting as a hydrogen-atom donor, is very important for the free radical scavenging effect of these compounds.
Platyphyllenone and platyphyllonol-5-O-β-d-xylopyranoside — both diarylheptanoids from Alnus species — showed high antiviral activity against influenza A virus H9N2 with EC50 values of 29.9 and 56.1 μM, respectively, compared to the positive control zanamivir; betulinic aldehyde exhibited anti-influenza effects against H9N2 avian influenza virus with an EC50 of 12.5 μg/mL. These findings are preclinical and have not been validated in human studies.
Evidence level: Preclinical (in vitro, some in vivo animal models); no clinical human trials identified.
Alder bark extract showed strong and concentration-dependent antioxidant activity in laboratory assays (IC50 0.15–12.21 µg/mL) and anti-inflammatory activity (IC50 5.47–12.97 µg/mL) in studies of closely related black alder. These data are derived from in vitro cell-based and chemical assays. No controlled human clinical trials on the antioxidant effects of red alder preparations have been identified in the peer-reviewed literature.
Evidence level: Preclinical (in vitro cell and animal models); no clinical human trials identified.
There are many reports testifying that extracts and isolated compounds from different Alnus species have significant antimicrobial, immunomodulatory, antioxidant, and anti-inflammatory activity. Key mechanistic work has been conducted using macrophage cell lines (see Section 4.1). Alder bark extract also showed promising anti-angiogenic activity, inhibiting vessel growth (IC50 23.39 µg/egg) and the release of an endogenous phosphatase alkaline enzyme (IC50 44.24 µg/embryo), leading to the conclusion that it is a promising source of antioxidant, anti-inflammatory, and angio-modulator compounds. All such findings remain at the level of cellular and lower-organism models.
Evidence level: Preclinical (in vitro); no clinical human trials identified.
Antimicrobial activity of fourteen diarylheptanoids isolated from the bark of black and green alder was reported against twelve bacterial species (five Gram-positive and seven Gram-negative) and eight fungal strains; the most sensitive bacterial species were Klebsiella pneumoniae and Pseudomonas aeruginosa (Gram-negative), and Streptosporangium longisporum and Bacillus subtilis (Gram-positive); among fungal strains, the most sensitive were Fusarium equiseti, F. tricinctum, Candida albicans, and Saccharomyces cerevisiae.
Oregonin and its aglycone were shown to be associated with the antibiotic activity exhibited by a red alder bark methanol extract. In a study evaluating six European tree bark species, all extracts enhanced wound closure and decreased ROS production in HaCaT cells, with alder and bird cherry bark extracts showing the strongest effects, and the antimicrobial assay revealed potent activity against Gram-positive pathogens, with alder bark extract showing the greatest efficacy. Note: this study used Alnus glutinosa (black alder) rather than Alnus rubra specifically, and all findings remain in vitro.
Evidence level: Preclinical (animal tumor models and in vitro); no clinical human trials identified.
Recent clinical studies have verified that red alder contains betulin and lupeol, compounds shown to be effective against a variety of tumors. However, it is important to contextualize this statement: the data on betulin and lupeol in cancer are predominantly preclinical. Lupane-type triterpenes such as betulin, betulinic acid, and lupeol have shown multiple bioactivities against different cancer cell lines and hold encouraging antitumor effects, including activity against lung, liver, stomach, colorectal, and breast cancers, but further research in vitro and in vivo, and human clinical trials, are required to elucidate their mechanisms of action and their whole therapeutic potential.
Oregonin and hirsutanonol are considered potential cancer chemopreventive agents based on in vitro data. Oregonin and hirsutanonol are potential cancer chemopreventive agents, though this designation applies specifically to preclinical results. Betulinic acid has been emphasized as a highly selective anti-melanoma agent and, as of publication of reviewed literature, was undergoing phase II clinical trials as a topical application, though this relates to betulinic acid across plant sources rather than to red alder preparations specifically.
Evidence level: Preclinical (cell models); limited in vitro human blood sample data; no completed controlled clinical trials identified.
Oregonin, an open-chain diarylheptanoid isolated from Alnus incana bark, possesses remarkable antioxidant and anti-inflammatory properties, inhibits adipogenesis, and has been proposed for use in the prevention of obesity and related metabolic disorders. Using ethnobotanical and bioassay screening techniques, two Boreal Forest plants — namely Alnus incana ssp. rugosa (Speckled Alder) and Populus balsamifera — were identified as potently inhibiting adipogenesis; a classical bioassay-guided fractionation approach using triglyceride accumulation in the 3T3-L1 adipocyte model cell line as the assay identified oregonin and salicortin as the respective active glycosides. These findings are directly relevant to red alder given its high oregonin content, but the work was performed on a related alder species, not Alnus rubra itself.
The effects of oregonin, isolated from the bark of grey alders growing in Latvia, have been tested in vitro on blood samples from volunteers with clinically confirmed metabolic syndromes. This represents preliminary ex vivo human data, but it is not a controlled clinical trial and its translational significance is uncertain.
Evidence level: Preclinical (in vitro cell models); traditional use well-documented; no clinical human trials identified.
Red alder (Alnus rubra) has been used traditionally by Indigenous peoples of the Pacific Northwest for a variety of medicinal purposes, including the treatment of scratches, abrasions, and other minor skin injuries. The historical use is documented in sources such as "Plants Used by the Indians of Mendocino County, California" (Chesnut, 1902) and "Native American Ethnobotany" (Moerman, 1998), which report its external application for wounds, sores, and skin irritations; however, scientific validation for these uses is limited.
In a multi-species bark extract study, alder bark extract enhanced wound closure and decreased ROS production in human keratinocyte (HaCaT) cell cultures; the authors highlighted the potential therapeutic application of such extracts in skin disorder treatment and as a validation of traditional medicinal practices. This study examined Alnus glutinosa specifically.
Evidence level: Traditional use only; preclinical rationale via salicin content; no clinical human trials identified.
An infusion of the bark has been used in the treatment of many complaints such as headaches, rheumatic pains, internal injuries, and diarrhea; externally, a poultice of the bark has been applied to eczema, sores, and aches. The presence of salicin provides a plausible pharmacological rationale for analgesic and antipyretic effects, but no clinical trials have been performed to establish efficacy or dose.
Evidence level: Traditional use only; no clinical human trials identified for red alder specifically.
The Blackfoot Confederacy used an infusion made from the bark of red alder to treat lymphatic disorders and tuberculosis. Red alder is also said to produce constituents which aid in clearing the lymph nodes, and is traditionally used by the Coast Salish peoples for this medicinal purpose. No peer-reviewed clinical studies have evaluated these applications in human populations.
Based on ethnobotanical records and preclinical science, red alder has been associated with the following body systems:
No standardized dosages for red alder (Alnus rubra) preparations have been established in pharmacopeial monographs or regulatory guidance documents (such as those of the German Commission E, ESCOP, or WHO). The preclinical literature uses the following concentrations and doses specifically:
No human clinical dosage information for red alder bark or extract has been identified in the peer-reviewed literature. Traditional preparations were administered as infusions, decoctions, and poultices without defined quantitative dose records.
Alder pollen is a major allergen. People allergic to alder often also react to birch pollen because of shared allergens. An extract from Alnus rubra pollen is formally used in allergy testing. Cross-reactivity between alder and birch pollen is well established within the Betulaceae family; individuals sensitized to one species should exercise caution with respect to the other.
The bark of red alder contains salicin, which is metabolized to salicylic acid in the body. The bark contains salicin, which probably decomposes into salicylic acid (closely related to aspirin) in the human body. Theoretical interactions with anticoagulant medications, non-steroidal anti-inflammatory drugs (NSAIDs), or aspirin — similar to those described for willow bark — may apply, though no pharmacokinetic or clinical interaction studies specific to red alder have been identified in the peer-reviewed literature.
People allergic to alder often also react to birch pollen because of shared allergens; oral allergy syndrome (OAS) is common among individuals sensitized to Betulaceae pollen. This is relevant for individuals consuming alder bark preparations orally.
No formal toxicological studies (including acute toxicity, subchronic toxicity, genotoxicity, reproductive toxicity, or carcinogenicity assessments) specific to Alnus rubra bark extracts or preparations have been identified in the peer-reviewed literature. No maximum tolerable doses, no-observed-adverse-effect levels (NOAELs), or established safe upper limits have been published for human consumption of red alder bark-derived products. The preclinical evidence base, while promising for several compound classes, remains almost entirely in vitro or in animal models, and no human clinical trials have established a safety profile.
Bark infusions were historically taken as a laxative and to regulate menstruation. This traditional use suggests potential uterotonic activity, raising theoretical concerns for use during pregnancy. No controlled data on safety in pregnant or lactating individuals, or in children, exist in the peer-reviewed literature.
Red alder (Alnus rubra) has a substantive and well-documented history of traditional medicinal use among multiple Indigenous North American peoples. Diarylheptanoids have become a focus of research following reports of their antioxidant, antifungal, and anti-cancer activities. Scientific investigations have validated several traditional applications and revealed diverse pharmacological properties, including anticancer, antioxidant, antibacterial, antifungal, anti-inflammatory, hepatoprotective, and wound-healing effects. However, as of the current literature, essentially all of this evidence is preclinical — derived from in vitro cell assays and, less commonly, animal models. No published controlled human clinical trials evaluating red alder bark extracts or preparations for any indication have been identified. The plant is characterized as little used in modern herbalism, and its constituent compounds (particularly oregonin, lupeol, betulin, and betulinic acid) represent active areas of phytochemical research with promising but as-yet unproven translational utility.
Health conditions that Red alder may help support.
Body systems that Red alder may help support.
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