Siberian Elm (Ulmus pumila L.): A Comprehensive Reference
1. Identity and Botanical Description
Taxonomy and Nomenclature
Ulmus pumila L., the Siberian elm, is a tree native to Asia, also known as the Asiatic elm and dwarf elm, though it is sometimes mistakenly called the "Chinese" elm (Ulmus parvifolia). It belongs to the family Ulmaceae. In Traditional Chinese Medicine, the bark is known as Yú Bái Pí (榆白皮), and in Korean traditional medicine the root bark of related Ulmus species is known as yugeunpi. The genus Ulmus L. is a typical member of the family Ulmaceae naturally distributed throughout the northern hemisphere in Eurasia, North America, and Northern Africa; according to the World Flora Online 2024, 44 species are reported as accepted species, including Ulmus pumila L., which possesses 21 synonyms.
Morphology and Natural Range
U. pumila has been widely cultivated throughout Asia, North America, Argentina, and southern Europe, becoming naturalized in many places, notably across much of the United States. The Siberian elm is usually a small to medium-sized, often bushy, deciduous tree growing to 25 m (82 ft) tall, the diameter at breast height reaching up to 1 m. In the wild, it is primarily found in moist soils along streams from eastern Siberia to China. It is native to Siberia, China, and Korea.
The leaves are alternate, simple, elliptical to ovate, 1 to 2½ inches long, with a singly serrated margin, a nearly equilateral base, dark green and smooth above, paler and smooth below. Flowers are small pale green clusters occurring in early spring before the leaves. The fruit is a thin, wafer-like samara, nearly round, notched at the top, about ½ inch in diameter, initially pale green, later turning light brown when ripe in spring.
Distinction from Slippery Elm
Siberian elm (U. pumila) is botanically and chemically distinct from slippery elm (Ulmus rubra or Ulmus fulva), the North American species most associated with medicinal mucilage in Western herbalism. In the central United States, native U. rubra hybridizes in the wild with the Siberian elm (U. pumila), which was introduced in the early 20th century and has spread widely since; the hybrid group is known as Ulmus × intermedia. Despite their relatedness, the two species have distinct phytochemical profiles and different primary medicinal traditions.
Common Forms and Preparations
The tree is harvested from the wild for local use as a food, medicine, and source of materials. The principal plant parts used medicinally are the inner bark (particularly of the root and stem), the leaves, and the flowers. Preparations documented in the scientific and ethnobotanical literature include:
- Decoction or water extract of inner bark: The inner bark contains special mucilage-containing sacs, and the hot water extract of the inner bark consists of pectic substances with excellent gelling and thickening properties.
- Bark flour and powder: The inner bark is the by-product of the elm tree industry and is the only edible part of a tree trunk; elm inner bark has traditionally been used for making noodles in China, while in western countries it has been used for making bark bread during times of famine.
- Ethanol extracts (root bark, stem bark, leaf): Used in laboratory and preclinical research contexts, typically prepared by macerating the plant material in 80–95% ethanol.
- Cold-water infusions: Preferred by some practitioners to maximize mucilage extraction from the dried bark.
2. Traditional and Historical Use
Traditional Chinese Medicine (TCM)
The dried inner bark of the Siberian elm tree has long been valued in Chinese herbal medicine under the name Yú Bái Pí (榆白皮) for its ability to clear heat, reduce swelling, promote urination, and support detoxification, particularly in conditions involving damp-heat, skin inflammation, and urinary discomfort. Its nature is described in TCM terms as sweet, bland, and slightly cold. In traditional use, Yu Bai Pi is taken to relieve edema, soothe inflamed skin, reduce abscesses, and clear heat-toxin, especially when symptoms involve redness, swelling, weeping sores, or difficulty urinating. It is commonly used both internally and externally for skin ulcers, boils, eczema-like eruptions, and damp-heat conditions affecting the lower burner. It has also been used traditionally for inflammatory conditions and gastric cancer.
Korean Traditional Medicine
The root bark of U. pumila has traditionally been used against infectious diseases in Korea. More broadly within the Korean tradition, closely related elm species occupy a prominent role: the bark of Korean elm species is used in traditional Korean medicine for dysuria, swelling, rhinitis, and inflammatory ulceration of the gastrointestinal tract. Ulmus species are large deciduous trees distributed throughout Korea, and their root and stem bark have been used to treat gastrointestinal diseases and wounds in folk medicine.
Mongolian and Central Asian Traditions
Ulmus pumila was used by Mongolians in the Ordos plateau as a wild vegetable. Local people cooked the immature fruit of Ulmus pumila in salted water. Nomadic Mongolians had not developed vegetable planting techniques historically, and so relied on the simple collective method of gathering uncultivated vegetables from the wild.
Food Use Traditions
Elm inner bark has traditionally been used for making noodles in China; in western countries it was used for making bark bread during times of famine. Today people attach importance to bark bread not only for the daily diet but also for following a sustainable, environmentally friendly, and healthy food system.
3. Key Constituents and Active Compounds
Overview of Phytochemical Classes
A 2024 phytochemical study of the leaves of U. pumila isolated a total of 32 compounds, including six flavonols, five dihydroflavones, three dihydroflavonols, three megastigmane glycosides, two triterpenoids, four sugars, one phenylpropanoid, two phenolic glycosides, two aromatic glycosides, one phenolic, one lignan glycoside, one steroid glycoside, and one fatty acid. Previous phytochemical investigations of U. pumila have mainly focused on the bark of this plant, revealing the presence of flavonoids, triterpenoids, and sesquiterpenoids.
Previous phytochemical investigations on the genus Ulmus have identified diverse types of compounds, including flavonoids, terpenoids, lignans, coumarins, and glycosides.
Flavonoids
Chromatographic separations of U. pumila extract have resulted in the isolation and purification of eight compounds: catechin, epicatechin, kaempferol-3-O-β-D-glucoside, kaempferol-3-O-β-D-galactoside, quercetin-3-O-β-D-glucopyranoside, quercetin-3-O-β-D-galactopyranoside, kaempferol-3-O-rutinoside, and kaempferol-3-O-robinobioside, as identified through spectroscopic analysis. A separate study isolated a new flavonoid, (−)-epicatechin-7-O-β-D-apiofuranoside, from Ulmus pumila. U. pumila L. was reported to possess large amounts of phenols and flavonoids with potent antioxidant activities.
Triterpenoids
Previous studies on the constituents of the root bark of this species led to the characterization of two potentially cytotoxic sesquiterpenoids, namely mansonones E and F, as well as various bioactive triterpenoids. Four triterpenoids — oleanolic acid, friedelin, maslinic acid, and arjunolic acid — were also isolated from the methanol extract of U. pumila L. Phytochemical examination of the stem bark and leafy branches of Ulmus pumila L. yielded 13 compounds: Friedelin, 3β-acetoxyurs-11-en-13β,28-olide, 3β-O-acetyl ursolic acid, 3β-O-acetyl oleanolic acid, β-sitosterol, stigmasterol, betulinic acid, methyl ursolate, methyl oleanolate, kaempferol-3-O-rutinoside, quercetin-3-O-β-D-glucopyranoside, quercetin-3-O-β-D-galactopyranoside, and caffeic acid.
Pectic Polysaccharides (Mucilage)
Four different monosaccharides were found in the pectic polysaccharides of U. pumila (PPU), including galacturonic acid, galactose, rhamnose, and glucose. FT-IR spectra indicated that the pectic polysaccharides were probably low methoxyl pectin. GC-MS and NMR analysis suggested the major monosaccharide was α-1,4-linked galacturonic acid with α-1,2-linked rhamnose as the backbone and glucose or galactose residues as branches. This mucilaginous polysaccharide fraction is structurally analogous to (though not identical with) the mucilage of slippery elm (U. rubra), and contributes to the soothing, demulcent properties attributed to elm bark preparations across Asian and Western traditions.
Other Constituents
According to earlier studies, U. pumila is known to contain steroidal chemicals such as β-sitosterol, phytosterol, and stigmasterol; terpenoid chemicals such as friedelin, epifriedelanol, and taraxerol; phenolics such as tannin; and polysaccharides such as starch. A phytochemical study on the stem bark extract of U. pumila L. led to separation of Icariside E4, which strongly inhibited nitric oxide generation in LPS-activated macrophages.
4. Scientific Evidence by Area of Use
4.1 Anti-Inflammatory Activity
In vitro evidence: Ulmus pumila L. has been reported to have antioxidant, anti-inflammatory, antimicrobial, and anti-adipogenic activities. Selenized pectic polysaccharides from U. pumila (Se-PPU) inhibited LPS-induced nitric oxide production in RAW 264.7 cells, and increasing selenium content enhanced the anti-inflammatory properties of PPU.
Animal (in vivo) evidence: In a Mongolian study, treatment with ethanolic and ethyl-acetate fractions of U. pumila L. reduced inflammatory symptoms, showing protective effects in a carrageenan-induced paw edema model in rats. These preliminary findings were reported to support its traditional medicinal use as a candidate for the treatment of inflammatory symptoms.
Strength of evidence: The anti-inflammatory evidence for U. pumila specifically is currently limited to in vitro cell-culture experiments and a small number of rodent models. No human clinical trials have been published. The results are considered preliminary.
4.2 Antimicrobial Activity
In vitro evidence (MRSA): In a published study (PMC3817893), root bark of Ulmus pumila was extracted with ethanol and then antimicrobial effects were tested on clinically isolated 12 MRSA strains and 1 standard MRSA strain. U. pumila showed antibacterial activities against all MRSA strains. The minimum inhibitory concentration (MIC) of U. pumila root bark against all MRSA strains revealed a range from 125 to 250 μg/mL. At sub-MIC concentrations (64–125 μg/mL), real-time PCR analysis showed inhibition of the genetic expressions of virulence factors such as mecA, sea, agrA, and sarA in standard MRSA. The results suggest the ethanol extract of U. pumila root bark may have antibacterial activity against MRSA related to its phytochemicals such as phenolics, steroids, and terpenoids, but further studies are needed to identify the specific active constituents.
In vitro evidence (gram-negative bacteria): Ethanol extracts of Ulmus pumila leaves and flowers were tested against gram-negative bacteria; U. pumila displayed antibacterial activity against P. vulgaris, E. coli, K. pneumoniae, and E. cloacae. With these results and previous activity against gram-positive bacteria, the authors noted much potential for Ulmus pumila to be developed into a broad-spectrum antibacterial agent.
Strength of evidence: All antimicrobial data are from in vitro disc-diffusion and MIC assays. No animal models or human clinical trials have been conducted to validate these findings. The evidence is preliminary.
4.3 Antioxidant Activity
In a study on the bark of Ulmus pumila L., enzyme-assisted extraction (using cellulase, pectinase, and β-glucosidase) at optimized conditions (pH 4.63, 52.6 °C, 62 min) yielded the highest polyphenol content at 16.04 mg gallic acid per gram of dry matter. U. pumila extract showed potent antioxidant activity as indicated by declined malondialdehyde and elevated reduced glutathione, catalase, and superoxide dismutase levels in Alzheimer's disease model rats' brains.
Strength of evidence: Antioxidant activity has been demonstrated both in vitro (DPPH, ABTS, and related assays) and in rodent models as a secondary outcome measure in neuroprotection studies. No independent human antioxidant trials have been published for this species specifically.
4.4 Neuroprotective Activity and Alzheimer's Disease Model
Animal study: A published study investigated the neuroprotective activity of Ulmus pumila L. leaves alcoholic extract in an AlCl₃-induced Alzheimer's disease model in rats. Rats were orally treated with AlCl₃ (17 mg/kg) for 4 weeks, followed by U. pumila extract (150 mg/kg body weight) for another 6 weeks. Treatment with U. pumila extract resulted in a significant regulation in neurotrophic factors — brain-derived neurotrophic factor (BDNF) and transforming growth factor-β (TGF-β) — and the pro-inflammatory cytokine TNF. It also induced an elevation in serum levels of monoamine neurotransmitters: norepinephrine, dopamine, and serotonin, and a decline in brain acetylcholinesterase activity. Histological improvement was detected in the cerebral cortex, the hippocampus, and striatum of the treated rats. Phytochemical analysis revealed high contents of flavonoids and phenolics. The extract and isolated compounds exerted prominent activity in an in vitro acetylcholinesterase inhibition assay.
In vitro enzyme inhibition: U. pumila extract and isolated compounds exerted prominent activity in the in vitro acetylcholinesterase inhibition assay, with kaempferol-3-O-β-glucoside being the most potent compound showing an IC₅₀ of 29.03 ± 0.0155 μM. A molecular docking study indicated high affinity of kaempferol-3-O-β-robinobioside on the acetylcholinesterase binding site, with an estimated binding free energy of −8.26 kcal/mol.
Strength of evidence: This evidence is entirely preclinical (one rodent model and in vitro assay data). No human clinical trials exist for U. pumila in neurological or cognitive conditions. The evidence is preliminary and hypothesis-generating only.
4.5 Anticancer / Cytotoxic Activity
Ulmus pumila L. leaves showed cytotoxicity against a human breast cancer cell line, indicating chemotherapeutic potential through induction of apoptosis. Betulinic acid isolated from U. pumila exhibited cytotoxic potential against MCF-7, HCT-116, and A549 cell lines with IC₅₀ values of 22.39 ± 0.09 μM, 22.29 ± 0.05 μM, and 42.33 ± 0.06 μM, respectively. The remaining triterpenoids showed cytotoxic potential against HCT-116 and MCF-7 cell lines with IC₅₀ values ranging from 48.91 ± 0.12 to 78.98 ± 0.07 μM. The demonstrated cytotoxic potential of betulinic acid was suggested as a lead compound for anticancer therapy.
Strength of evidence: All anticancer data are from in vitro cell-line experiments only. No animal tumor models or human studies have been conducted on U. pumila specifically. This constitutes the earliest, weakest level of preclinical evidence.
4.6 Anti-Adipogenic Activity
An active extract of Ulmus pumila has been reported to inhibit adipogenesis through regulation of cell cycle progression in 3T3-L1 cells (Ghosh et al., 2012). This in vitro finding suggests a potential role in metabolic regulation, but has not been extended to animal or human studies.
Strength of evidence: Single in vitro cell-culture study. Evidence is preliminary and requires extensive further investigation.
4.7 Food and Nutritional Applications
Elm bark (Ulmus pumila L.) flour has been characterized as a nutritious and sustainable edible material for developing the macromolecular network in the food matrix. Studies have investigated the effects of elm bark flour and water addition on the technological and sensory characteristics of gluten-free whole foxtail millet bread. Results showed that elm bark flour improved gelatinization characteristics and rheological properties of gluten-free dough. The porous and network structure of the gluten-free bread was confirmed by FTIR and X-ray diffraction, yielding higher specific volume (1.98 ± 0.13 cm³/g) and decreased hardness from 97.43 to 11.56 N.
5. Body Systems and Health Areas
- Gastrointestinal system: Traditional use across Chinese and Korean medicine for GI tract inflammation, gastric conditions, and damp-heat disorders. The mucilaginous pectic polysaccharides in the inner bark provide demulcent and soothing activity on mucosal surfaces.
- Urinary system: In Traditional Chinese Medicine, Yú Bái Pí is used to clear heat, promote urination, reduce swelling, and detoxify; it is commonly applied for edema and difficult urination.
- Integumentary system (skin): Traditional use includes internal and external application for skin ulcers, boils, eczema-like eruptions, and damp-heat conditions.
- Immune / inflammatory system: Anti-inflammatory activity demonstrated in vitro and in rodent models via inhibition of nitric oxide production and suppression of pro-inflammatory mediators.
- Nervous system: Preclinical studies have investigated acetylcholinesterase inhibition and neuroprotection in an Alzheimer's disease rat model, with regulation of BDNF and monoamine neurotransmitter levels observed.
- Antimicrobial / infectious disease: In vitro activity against MRSA and gram-negative bacteria such as E. coli, K. pneumoniae, P. vulgaris, and E. cloacae.
- Metabolic: Anti-adipogenic effects shown in cell culture; potential relevance to metabolic syndrome research is speculative at this stage.
6. Dosage Forms and Dosages Reported in Studies
No standardized therapeutic dosages for human use have been established for Ulmus pumila in any recognized pharmacopoeia or regulatory monograph. The following dosages and forms appear in the primary scientific literature:
- Animal model (neuroprotection): Rats were orally treated with AlCl₃ (17 mg/kg) for 4 weeks followed by U. pumila extract at 150 mg/kg body weight for another 6 weeks.
- Animal model (immunomodulation, U. davidiana var. japonica bark water extract): B6 mice were given 5 g/kg of bark water extract once daily for 14 days.
- In vitro antimicrobial (MRSA): The MIC of U. pumila root bark ethanol extract against MRSA strains was in a range from 125 to 250 μg/mL.
- In vitro anti-inflammatory (pectic polysaccharides): Selenized PPU from U. pumila was shown to inhibit LPS-induced nitric oxide production in RAW 264.7 macrophage cells at concentrations studied using sodium selenite concentrations of 0.2 and 0.4%.
- Extraction for polyphenol yield: Enzyme-assisted extraction of U. pumila bark yielded the highest polyphenol content of 16.04 mg gallic acid per gram of dry matter under optimized conditions.
All dosages above are from preclinical research contexts and cannot be translated directly into human supplementation recommendations.
7. Safety Considerations and Interactions
Formal human safety data for Ulmus pumila as a dietary supplement are absent from the peer-reviewed literature. No controlled safety trials, case-control studies, or systematic adverse-event reports specific to U. pumila preparations have been indexed in PubMed/PMC at the time of this writing. The following observations are based on available evidence:
- Distinguishing from slippery elm (U. rubra): Ulmus pumila is not the same species as slippery elm (Ulmus rubra), which has a separate regulatory and monographic status. Slippery elm preparations were used in Native American traditional medicine for gastrointestinal and urinary tract disorders and topically for skin diseases; the active ingredients appear to be mucilages, but the inner bark is also rich in tannins and resins which are astringents. Users and clinicians should not assume safety data from one Ulmus species applies to another.
- Tannin and phenolic content: U. pumila root bark phytochemical analysis showed a relatively high content of phenolics, steroids, and terpenoids. The researchers suggested the antibacterial activity may be related to these chemicals. High tannin content in herbal preparations is generally associated with potential for gastrointestinal irritation at elevated doses and may theoretically interfere with absorption of iron and certain pharmaceutical compounds.
- Presence of cytotoxic sesquiterpenoids: Previous studies on the root bark of U. pumila led to characterization of two potentially cytotoxic sesquiterpenoids, namely mansonones E and F. The significance of these compounds at doses achievable through food or supplement preparations has not been assessed in safety studies.
- Invasive species and contamination risk: In some areas, this tree is considered weedy and borderline invasive. Material sourced from environmental collections may carry risks associated with pesticide exposure, heavy metal uptake in disturbed soils, or misidentification, particularly confusion with U. parvifolia (lacebark elm).
- Lack of human clinical safety data: No published human clinical trials, toxicological studies, or pharmacokinetic studies have been conducted for U. pumila-specific preparations. The preclinical in vitro and rodent data, while promising for investigation, cannot be used to establish human safety profiles.
- Potential drug interactions: Given the presence of flavonoids that inhibit acetylcholinesterase in vitro (notably kaempferol-3-O-β-glucoside with an IC₅₀ of ~29 μM), theoretical interactions with cholinergic medications cannot be excluded but have not been demonstrated in any clinical context. Similarly, the tannin and polyphenol content carries a theoretical potential for interactions with drugs known to be affected by polyphenol co-administration (e.g., certain antibiotics, iron supplements), but this has not been formally studied for U. pumila.
8. Summary of Evidence Strength
The preponderance of scientific research on Ulmus pumila as a medicinal or supplemental ingredient is currently at the preclinical stage. Deciduous trees of Ulmus species have been reported in preclinical contexts to exhibit antibiotic, antifungal, antioxidant, anti-inflammatory, hepatoprotective, neuroprotective, antiangiogenic, and antiviral effects, attributed largely to their flavonoid richness. However, as of the available published literature, no completed randomized controlled trials, cohort studies, or systematic reviews in human populations have been published specifically for U. pumila. Traditional use across Chinese, Korean, and Mongolian cultures provides historical context for biological plausibility but does not constitute clinical proof of efficacy or safety. Researchers have called for additional studies to identify the specific active constituents and confirm effects at physiologically relevant concentrations in humans.
References
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