Aspen

Other Names

Álamo TemblónAmerican AspenAspeAspen PoplarCommon AspenEspeEurasian AspenEuropean AspenFaux-trembleGolden AspenMountain AspenPeuplier Faux-TremblePeuplier tremblePeuplier tremble d'AmériquePopplePopuli CortexPopuli FoliumPopulus aureaPopulus tremulaPopulus tremula ssp. tremuloidesPopulus tremula subsp. tremuloidesPopulus tremuloidesPopulus tremuloides var. aureaPopulus tremuloides var. cercidiphyllaPopulus tremuloides var. intermediaPopulus tremuloides var. magnificaPopulus tremuloides var. rhomboideaPopulus tremuloides var. vancouverianaPopulus vancouverianaQuakiesQuaking AspenQuaking PoplarQuiver-leafQuivering AspenShivering PlantTrembleTremble américainTrembling AspenTrembling PoplarWagging TongueWhite PoplarZitter-Pappel

Synopsis

Aspen (Populus tremula / Populus tremuloides): A Comprehensive Reference

1. Identity and Botanical Classification

Species and Nomenclature

The most commonly used species for herbal remedies are the American aspen (Populus tremuloides Michaux) and the European aspen (Populus tremula L.). Quaking aspens are members of the Order Malpighiales (or Rhizophorales), the Family Salicaceae, and the Tribe Saliceae. Previous scientific synonyms for P. tremuloides include Populus aurea Tidestrom and P. cercidiphylla Britton.

The common name "Aspen" derives from the Old English word aespe. Other common names for P. tremuloides include American Aspen, American Poplar, Canadian Aspen, Golden Aspen, Mountain Aspen, Quaking Aspen, Quaking Poplar, Quiver Leaf, and Popple. In pharmacy and commerce, the European aspen bark is sometimes listed under the Latin names Populi Cortex (bark) and Populi Folium (leaf). Additional names encountered in commerce include Álamo Temblón, Peuplier Faux-Tremble, Trembling Aspen, and Zitter-Pappel.

Botanical Description and Natural Range

Quaking aspen (Populus tremuloides) is a tree largely present in the boreal forests of North America and Eurasia. This broadleaf tree exhibits the largest spatial distribution of all deciduous species in Canada, stretching from Newfoundland and Labrador to British Columbia and Yukon. The American species is a deciduous hardwood native to boreal and montane North America — from Alaska to Newfoundland, south through the Rockies to northern Mexico.

The aspen has a columnar trunk that can reach up to 35 m in height and several meters in diameter. The tree lives on average 80–90 years, rarely up to 150 years. Young aspens have smooth bark, light green or gray-green, which cracks and darkens with age.

Parts Used and Common Preparations

The leaves, bark, and buds of Populus tremuloides are used medicinally. The bark is harvested from side branches or coppiced trees and dried for later use. Preparations of aspen include infusions, tinctures, and salves, often used to treat rheumatic and arthritic pain. In decoction form, one to four grams of aspen bark are boiled to obtain a concentrated liquid that can be taken to relieve joint pain and fever, as well as for stopping diarrhea. The leaf buds are also used as a salve for colds, coughs, and irritated nostrils.

In cosmetic and personal care manufacturing, aspen bark extract is produced as a standardized powder. PhytoCide Aspen Bark Extract Powder is a naturally-derived, water-soluble botanical antimicrobial standardized to 54–60% salicylates for cosmetic use. This product is GMO-free and no ethoxylation, irradiation, sulphonation, hydrogenation, or ethylene oxide is used in processing; the solvent used for extraction is simply water.

2. Traditional and Historical Use

Indigenous North American Use

American aspen has a long history of herbal use. It was widely employed medicinally by many native North American Indian tribes who valued it especially for its antiseptic and analgesic qualities, using it in the treatment of wounds, skin complaints, and respiratory disorders. Quaking aspen was formerly used in traditional medicine by Native American nations of Québec for its various therapeutic functions, either as a vermifuge, to treat venereal disease, as an anti-arthritis agent, or as a cure for colds.

Native American uses include: root bark tea for excessive menstrual flow; poultices made of the root for cuts and wounds; and a tea made of the inner bark for venereal disease, stomach pain, urinary ailments, worms, colds, and fevers. The Cree and Delaware peoples traditionally simmered aspen bark to create a decoction for treating coughs and symptoms of the common cold.

The inner bark was used as an antiscorbutic, a diaphoretic, a diuretic, an expectorant, a febrifuge, a purgative, and a vermifuge. Records indicate that P. tremuloides was utilized as a medicinal plant by Indigenous groups across the continent; most notably, the crushed leaves, stems, roots, and bark of this species were applied as a poultice to stings and minor wounds.

European Herbal Tradition

The aspen tree (Populus tremula and related species) has a long-standing history in traditional medicine, particularly among Native American and European herbalists. Internal uses in European herbalism include the treatment of rheumatism, arthritis, gout, lower back pains, urinary complaints, digestive and liver disorders, debility, and anorexia, as well as to reduce fevers and relieve the pain of menstrual cramps. Externally, the bark was used to treat chilblains, haemorrhoids, infected wounds, and sprains.

The five-component herbal formula Eviprostat, which contains a Populus tremula extract among other botanical extracts, originated in European folk medicine. In Europe these plants were originally used as folk medicines for benign prostatic hyperplasia (BPH), prostatitis, cystitis, and epididymitis.

Historical Context of Salicin Discovery

Both P. tremuloides and P. tremula produce bark rich in salicin (CAS 138-52-3, C₁₃H₁₈O₇), the glycoside precursor to salicylic acid and, historically, to aspirin. It was Populus and Salix bark that Johann Buchner extracted to isolate salicin crystals in 1828 — a step toward the synthesis of acetylsalicylic acid in 1897.

3. Key Constituents and Active Compounds

Phenolic Glycosides (Salicinoids)

Like other Salicaceae, the genus Populus is characterized by a diversity of phenolics; in particular, the salicin-based phenolic glycosides are found in leaves and bark of all species examined. These phytochemicals consist of glucosides of salicyl alcohol, which are generally further esterified and benzoylated. Tremulacin and salicortin are particularly common in P. tremuloides, but related glycosides are present at varying levels in other species.

Using UHPLC-ESI/TOFMS operating in negative ionization mode, researchers identified nine salicylate-like phenolic glycosides in P. tremula leaves: salicin, salicortin, tremuloidin, tremulacin, 2′-O-acetyl-salicin, 2′-O-acetyl-salicortin, salicyloyl-salicin, 2′-O-cinnamoyl-salicortin, and acetyl-tremulacin.

Salicin is a natural compound found in aspen bark and leaves. It is a glycoside of salicylic acid and has anti-inflammatory and analgesic (pain-relieving) properties. Salicin is the natural precursor of the synthetic drug aspirin. The bark of Populus tremuloides contains salicin, an aspirin-like substance. It is considered anti-inflammatory, analgesic, and slightly sedative. Salicin breaks down in the body to salicylic acid, a substance related to the active ingredient in aspirin.

Additional Phenolic and Flavonoid Constituents

Aspen buds contain glycosides salicin and populin, benzoic and malic acid, tannins, essential oil, carbohydrates, and other compounds. The leaves contain carbohydrates, organic acids, carotenoids, vitamin C, carotene, flavonoids, phenolglycosides, anthocyanins, and tannins.

Phenol glycosides can be used as anthelmintic agents (especially against opisthorchiasis), while tannins, organic acids, essential oils, and bitter substances give the plant choleretic, anti-inflammatory, bactericidal, and spasmolytic properties.

Aspen contains various polyphenolic compounds, such as flavonoids and tannins, which have antioxidant properties that help protect against oxidative stress. Aspen leaves and bark may contain essential oils with aromatic and potentially medicinal qualities; these oils can vary in composition and may include terpenes and volatile organic compounds.

Research on P. tremula knotwood has identified novel antioxidant compounds: complete characterization of two compounds obtained from acetone extract of P. tremula knotwood was achieved using LC-DAD-MS, MS/MS, IR, and NMR; the new compounds were unequivocally identified as a mixture of the ester isomers of the (E) and (Z) p-coumarate of 1-O-rutinose. The isomers showed the capacity to inhibit lipid peroxidation and to trap peroxyl radicals, and also showed a significant ORAC (oxygen radical absorbance capacity) value of 11.7 μM TE (Trolox Equivalents).

Chemotypic Variation

Studies have measured average percentages of 19 salicinoids from the foliage of different P. tremula clones grown in two different environments. Identified chemotypes include 2′-cinnamoyl, 2′-acetyl, 2′-cinnamoyl/2′-acetyl, and tremuloides-like variants, with salicinoids including salicortin, tremulacin, salicin, tremuloidin, HCH-salicortin, HCH-tremulacin, salicyloylsalicin, and related acetyl and cinnamoyl derivatives. This chemotypic variation means the precise salicinoid content and profile can differ among individual trees and geographic populations.

4. Mechanisms of Action

Salicylate Pathway

Salicin is metabolized by the liver into salicylic acid, the active ingredient in aspirin. These salicylate compounds have antipyretic, analgesic, anti-inflammatory, antirheumatic, and anticoagulant effects in humans and animals. By reducing prostaglandin synthesis, aspen bark decreases inflammation, alleviates pain, and helps lower fever.

Antioxidant and NF-κB Pathways

In laboratory studies of the Eviprostat components (of which the Populus tremula extract is one), the effects of each component on reactive oxygen species (ROS), superoxide anion (O₂⁻), and hydroxyl radical (OH) generated in cell-free systems and human neutrophils were investigated. The P. tremula component (EVI-2) suppressed O₂⁻ levels in the xanthine/xanthine oxidase system, and abolished OH produced in a Fenton-type reaction system.

Closely related Populus species have provided mechanistic insights into anti-inflammatory signaling. In a study of P. deltoides leaf extract: the extract effectively inhibited the expression of inducible nitric oxide synthase (iNOS) and nitric oxide (NO) production in LPS-stimulated RAW 264.7 cells. Proinflammatory TNF-α levels were also reduced. The extract inhibited the phosphorylation of NF-κB and IκBα, and blunted LPS-triggered nuclear translocation of NF-κB p65. In MAPK signaling, it effectively decreased the phosphorylation of p38 and JNK, but not of ERK1/2. While this study was conducted on a related Populus species rather than aspen itself, the shared class of phenolic glycoside constituents makes the findings informative for understanding genus-level mechanisms.

Salicin exhibits anti-irritative properties in topical dermatological applications, shows an anti-aging effect on the skin, and the addition of salicin to collagen film improves material adhesion to the skin, which can be a valuable feature in biomaterial applications.

5. Scientific Evidence by Area of Use

5.1 Musculoskeletal Pain, Rheumatism, and Arthritis

Aspen is used for rheumatoid arthritis, nerve pain, and pain due to pressure on the sciatic nerve (sciatica), but there is no good scientific evidence to support these uses. Aspen is used in combination with other herbs for treating joint pain (rheumatism), prostate discomforts, back trouble (sciatica), nerve pain (neuralgia), and bladder problems.

No large, randomized controlled trials have been conducted evaluating aspen bark alone for musculoskeletal conditions. A 2022 review in the journal Molecules highlighted ongoing investigation into plant-derived salicylates for their potential in managing chronic inflammatory diseases, noting their favorable profile regarding gastrointestinal side effects compared to synthetic NSAIDs when used correctly. However, a significant limitation is the lack of large-scale, modern clinical trials specifically on Populus tremuloides for pain relief.

The closest analogy in the clinical literature is willow bark (Salix spp.), which shares key salicinoid constituents with aspen and has been more extensively studied. The reference to "anti-inflammatory activity of flavonol glycosides and salicin derivatives from the leaves of Populus tremuloides" appeared in Planta Medica (1990), but no modern human RCT directly evaluating aspen bark monotherapy for joint or back pain has been identified in peer-reviewed literature.

Evidence strength: Preclinical (in vitro/animal) and traditional use only; no robust human clinical trials established for this indication.

5.2 Fever Reduction

The chief historical use of Populus tremuloides is for intermittent fevers. The salicylate compounds responsible for antipyretic action have well-characterized pharmacological mechanisms in pharmaceutical aspirin, and these compounds have antipyretic effects in humans and animals. However, no clinical trials have specifically evaluated aspen bark preparations as an antipyretic in human subjects.

Evidence strength: Mechanistically plausible based on constituent pharmacology; no human clinical trial data specific to aspen bark.

5.3 Benign Prostatic Hyperplasia (BPH) and Urinary Tract Symptoms

Inflammation is a common finding in benign prostatic hyperplasia (BPH). The phytotherapeutic agent Eviprostat is a popular treatment for BPH in Japan and Germany. Eviprostat consists of five components; four are extracted from Chimaphila umbellata, Populus tremula, Pulsatilla pratensis, and Equisetum arvense, and the fifth is germ oil from Triticum aestivum.

An open, multicenter clinical trial was conducted in 100 patients with BPH. Patients received a 12-week oral administration of Eviprostat, 2 tablets per time, 3 times a day. After a 12-week therapy, IPSS, QOL score, Qmax, and Qave were significantly improved. IPSS was averagely decreased by 5.67 (P < 0.001); QOL score was averagely decreased by 1.44 (P < 0.001); Qmax was averagely increased by 1.70 ml/s (P < 0.001); Qave was averagely increased by 1.15 ml/s (P < 0.001); Ru was averagely decreased by 5.07 ml (P = 0.046).

A further study compared the standard Eviprostat tablet to EVI-F, a new formulation containing twice the active ingredient content (including P. tremula extract) designed to reduce the number of tablets per dose by half. Patients with BPH were randomly assigned to either the Eviprostat group (6 tabs/day) or EVI-F group (3 tabs/day) using the envelope method. Clinical efficacy was evaluated by the International Prostate Symptom Score (IPSS) and QOL score at the end of the treatment period, and safety was evaluated by the incidence of side effects.

Eviprostat is a phytotherapeutic agent widely used in the treatment of prostatic hypertrophy and has been used in Japan and Germany for more than 40 years. It is important to note that all BPH/urinary clinical research involves Eviprostat as a multi-herb combination product; no clinical trial has isolated the contribution of the Populus tremula component alone.

Evidence strength: Moderate clinical evidence exists for the multi-herb combination Eviprostat containing P. tremula; the specific contribution of the aspen extract within the combination cannot be determined from available studies.

5.4 Antimicrobial Activity

The continual emergence of pathogen resistance has pushed research into antimicrobial compounds. Researchers investigated compounds from quaking aspen trees (Populus tremuloides) as potential antimicrobial agents, and several extractions using different solvents were performed with antimicrobial activity tested against eight microorganisms. Results revealed that polar extraction solvents including water, ethanol, and methanol gave the best extraction yields (>15.07%). Minimal inhibition concentration (MIC) and minimal bactericidal/fungicidal concentration (MBC/MFC) data demonstrated that water extracts had the best antimicrobial activity by a weak to moderate inhibition of growth of all eight tested microorganisms, in addition to having a bactericidal effect on three of them. The methanol extract also displayed antimicrobial activity but to a lower level than the water extract.

Both ethanol and water/ethanol extracts of Populus buds revealed relatively higher activity against Gram-positive bacteria and fungi than against most Gram-negative ones.

In applied cosmetic settings, challenge testing has been carried out: a Double Challenge Test was completed using 2% PhytoCide Aspen Bark Extract Powder in a generic cream base formulation. Samples were inoculated with E. coli, P. aeruginosa, S. aureus, A. brasiliensis, and C. albicans. During the first 28-day incubation period, samples were periodically collected and tested for the presence of these microorganisms; following this initial 28 days, the cream samples were then re-inoculated and sampled over an additional 28-day period.

Evidence strength: In vitro evidence (laboratory and cosmetic challenge testing) for antimicrobial activity is present; no in vivo clinical trials in humans for infection treatment.

5.5 Antioxidant Activity

Populus extract has high therapeutic potential because of its antioxidant, anti-inflammatory, hepatoprotective, antitumor, and antimicrobial properties. The antioxidant capacity of P. tremula knotwood compounds has been quantified in vitro, with novel phenyl disaccharides isolated showing significant ORAC values. The Populus tremula extract component of Eviprostat (EVI-2) was shown to suppress superoxide anion levels in the xanthine/xanthine oxidase system and to abolish hydroxyl radicals produced in a Fenton-type reaction system.

Evidence strength: In vitro evidence for antioxidant activity; no controlled human trials.

5.6 Urinary and Diuretic Effects

Aspen bark has historically been used as a diuretic and as a treatment for gonorrhea. It is used internally in the treatment of urinary complaints and digestive and liver disorders. The individual components of Eviprostat, including P. tremula extract, are known to have diuretic, antiseptic, and anti-inflammatory effects. These claims are grounded in traditional use and the multi-herb Eviprostat combination product literature; no standalone human clinical trials on aspen for urinary tract conditions have been identified.

Evidence strength: Traditional use and indirect evidence from combination-product studies; no standalone clinical trial data.

6. Body Systems and Health Areas of Association

Musculoskeletal system: The stem bark is anodyne, anti-inflammatory, antiseptic, astringent, diaphoretic, diuretic, febrifuge, nervine, and stimulant, supporting traditional use for rheumatism, arthritis, gout, and back pain.
Immune/Inflammatory system: By reducing prostaglandin synthesis, aspen bark decreases inflammation, alleviates pain, and helps lower fever.
Urogenital system: Traditional uses include benign prostatic hypertrophy (BPH), cystitis, and urinary ailments.
Gastrointestinal system: An infusion of the bark is said to be helpful for chronic diarrhea, and the bark has been used historically for digestive and liver disorders.
Integumentary (skin) system: Salicin exhibits anti-irritative properties in topical dermatological applications and shows an anti-aging effect on the skin.
Respiratory system: An infusion of the inner bark is considered a remedy for coughs and an appetite stimulant.

7. Dosage Forms and Reported Dosages

Aspen preparations are largely homemade, so they are not standardized. The following dosages are reported in herbal and clinical reference sources:

Decoction (oral): One to four grams of aspen bark boiled to obtain a concentrated liquid, taken to relieve joint pain and fever, as well as for stopping diarrhea.
Eviprostat (multi-herb combination, oral): In the reported BPH clinical trial, patients received 2 Eviprostat tablets per dose, 3 times a day (6 tablets/day), for 12 weeks. An updated formulation (EVI-F) containing double the active ingredient content was tested at 3 tablets/day.
Cosmetic/topical (standardized bark extract): Recommended use levels for PhytoCide Aspen Bark Extract Powder in cosmetic formulations are 0.2%–3.0% of the finished product.

The appropriate dose of aspen for internal use depends on several factors such as the user's age, health, and several other conditions. No standardized therapeutic dosage range for oral aspen bark preparations in isolation has been established in peer-reviewed human clinical trials.

8. Safety Considerations and Interactions

Aspirin Cross-Reactivity

Aspen contains chemicals that are similar to aspirin. It may cause a reaction in people who are allergic to aspirin. Salicylates in aspen can cause allergic reactions in people who are sensitive to aspirin.

Contact Dermatitis

There is at least one previous report of allergic contact dermatitis from salicyl alcohol in aspen bark; a second case was documented with concomitant allergy to salicylaldehyde. An elk researcher who had handled leaves from various trees presented with eczema of the hands, face, flexures, trunk, and extremities; patch testing showed sensitivity to salicyl alcohol, salicylaldehyde, balsam of Peru, aspen wood dust, and an extract prepared from the bark of Populus tremula. Analysis found salicyl alcohol and salicylaldehyde in the bark extracts at approximately 0.9 micrograms per milligram in aspen bark.

Skin reactions, such as rashes, can occur after handling aspen leaves or bark.

Gastrointestinal Effects

Aspen contains chemicals that are similar to aspirin, and this may make stomach ulcers worse. Willow, aspen, and birch have not been demonstrated to cause peptic ulcer or gastrointestinal bleeding at usual therapeutic doses. However, they can cause nausea, which is usually easily remedied by taking them with food.

Drug Interactions

Aspen contains chemicals that are similar to aspirin. There is some concern that taking aspen along with aspirin might increase the effects and side effects of aspirin. Caution should be exercised when using aspen, particularly for individuals with bleeding disorders or taking anticoagulants.

There is, however, no established reason to avoid combining natural aspen salicylates with aspirin or anticoagulant medications out of concern for increased risk of bleeding, and natural salicylates cannot be substituted for aspirin in reducing the risk of atherosclerotic complications, as far as is known.

Gout and Blood Coagulation Disorders

Aspen contains aspirin-like chemicals that may make gout worse. Aspen contains chemicals similar to aspirin that may make some blood disorders associated with low prothrombin levels (hypoprothrombinemia) worse.

Pediatric Use and Reye's Syndrome

There is no information available about natural salicylates and Reye's syndrome; for the sake of greatest safety, they should be avoided in children with influenza until more information is available.

Pregnancy and Lactation

There is not enough reliable information to know if aspen is safe to use when pregnant or breastfeeding.

9. Commercial Cosmetic and Topical Applications

Aspen bark can be considered a potential source of salicin and salicylates. Due to the high content of salicylates, American aspen (Populus tremuloides) bark water-soluble extracts are commercialized as cosmetic components with skin conditioning and antimicrobial properties. The CAS number 90083-05-9 designates the bark extract — a cosmetic ingredient standardized for salicin content (54–60%, PhytoCide by Active Micro Technologies), used as a natural antimicrobial preservative.

The application of the microwave-assisted extraction technique for the isolation of salicin and related compounds from the bark of European aspen (Populus tremula) can enhance the concentration of biologically active compounds in water extracts and promote its use as a source of valuable products for cosmetics and pharmaceutics.

The cosmetic ingredient listing in this context is Populus Tremuloides Bark Extract (INCI name). It is derived from the bark of the aspen tree which is rich in salicylates that may function as the plant's natural defense mechanism against invading parasites.

10. Summary of Evidence Landscape

Aspen (Populus tremula / Populus tremuloides) has a well-documented ethnobotanical history spanning multiple indigenous North American cultures and European herbal traditions, centered on the salicylate content of its bark. The phytochemistry is well characterized at the analytical level, with at least nine distinct salicinoid phenolic glycosides identified in P. tremula leaves. Aspen bark contains bioactive constituents such as salicin, populin, and flavonoids, which are believed to offer anti-inflammatory and antioxidant effects. While comprehensive clinical trials are limited, in vitro and animal studies have demonstrated the potential of aspen extracts to modulate inflammatory pathways and reduce oxidative stress.

The most clinically developed application is the multi-herb Eviprostat formulation, which has been studied in BPH patients in Japan and Germany, but the specific contribution of the aspen component cannot be isolated from available trials. For musculoskeletal pain, fever, and urinary conditions — the traditional core indications — more evidence is needed to rate the effectiveness of aspen for these uses.

References

Health Conditions

Health conditions that Aspen may help support.

No conditions available.

Body Systems

Body systems that Aspen may help support.

No body systems available.