Home Ingredients Ash Leaf (Fraxinus excelsior)

Ash Leaf (Fraxinus excelsior)

Fraxinus excelsior L. or Fraxinus angustifolia Vahl (and hybrids), folium
Evidence Level
Preliminary
3 Clinical Trials
5 Documented Benefits
1/5 Evidence Score

Ash leaf is the dried leaf of the European ash (Fraxinus excelsior) or narrow-leafed ash (Fraxinus angustifolia), trees of the olive family. It is taken as a tea or as powdered leaf in capsules. In the EU, ash leaf tea is registered only as a traditional herbal medicine for relief of minor joint aches and to increase urine flow as an add-on in minor urinary complaints, based on more than 30 years of use in Spain. European regulators found no clinical study of ash leaf, and a later review of 1,455 newer papers found none relevant. Research on the leaf itself is limited to lab tests on human immune cells and older rat work. The aspen, ash and goldenrod product Phytodolor uses ash bark, not leaf, and ash seed extracts are a different product. The EU monograph advises against use under 18, in pregnancy or breastfeeding, and by anyone told to limit fluids.

Studied Dose No dose has been tested in a human trial of ash leaf alone. EU traditional-use doses for adults: 20 g dried leaf per liter of water as a decoction, or 10 to 30 g per liter as an infusion, split into 2 to 3 doses a day, with plenty of fluid.
Active Compound Dried leaves of Fraxinus excelsior and/or Fraxinus angustifolia. The European Pharmacopoeia requires at least 2.5% total hydroxycinnamic acid derivatives (as chlorogenic acid). The leaf also contains secoiridoids (oleuropein, ligstroside), verbascoside, flavonoids (about 1.4%, including rutin), mannitol (about 16% to 29%), mucilage, tannins and potassium. Coumarins such as fraxin and esculin occur only in traces. The EMA recognizes no single active constituent.

Benefits

Traditional ash leaf tea for minor joint aches

The European Medicines Agency's herbal monograph accepts ash leaf tea as a traditional herbal medicine for relief of minor joint aches. This rests only on long-standing use: ash leaf teas had been sold in Spain for more than 30 years when the agency reviewed it. The agency found no clinical data, and the monograph advises seeing a doctor if symptoms last beyond 4 weeks or joint pain comes with swelling, redness or fever.

Supported by Trial 1

Traditional urinary flushing use with plenty of fluid

The EU monograph also accepts ash leaf as a traditional herbal medicine to increase the amount of urine and flush the urinary tract as an add-on in minor urinary complaints. It requires adequate fluid intake, rules out use when fluids must be restricted, and advises a doctor if symptoms last beyond 2 weeks or fever, painful urination or blood in the urine appear.

Supported by Trial 2

Clinical research on ash leaf on its own

European regulators found no human pharmacology, efficacy or safety studies of ash leaf. A later periodic review screened 1,455 newer references and judged none relevant, and found no adverse reaction reports in the EU EudraVigilance database. The joint and urine uses therefore have no trial support in people.

Supported by Trial 1

Inflammation signals in human immune cells (lab studies)

Lab work only. Infusions of ash leaf samples from commercial and natural sources reduced reactive oxygen species and cytokine output from human neutrophils, and an infusion and compounds isolated from it, such as ligstroside, lowered TNF-alpha and IL-6 from stimulated human monocytes. Solvent extracts of the leaves also cut TNF-alpha and IL-12 in a human cell line. None of this has been tested in people.

Supported by Trial 1, Trial 3

Urine sodium output in rats (animal study)

Animal work only, known only from secondhand summaries. The EMA, citing a later review of a French rat study, reports that a water extract of spray-dried ash leaf powder had no effect while an alcoholic extract raised urinary sodium concentration. Another review it cites describes dose-dependent rises in sodium, chloride and potassium excretion. No study has measured urine output in people taking ash leaf.

Supported by Trial 2, Trial 3

Mechanism of action

1

Phenolic acids, secoiridoids and flavonoids

Analyses of ash leaf from commercial and natural sources found 64 compounds, led by chlorogenic acid, rutin, verbascoside and the secoiridoids oleuropein and ligstroside. The EMA suggests these flavonoids, iridoids and secoiridoids may together explain the traditional joint use, an idea not yet tested in people.

2

Mannitol and potassium as proposed contributors to urine flow

Dried ash leaf is rich in mannitol (about 21% in French samples, with a reported range of 16% to 29%) and contains about 1.7% potassium. The EMA proposes mannitol as a possible cause of the leaf's mild diuretic and laxative reputation, while older work credits flavonoids. Neither explanation has been checked in human studies.

3

Coumarins such as fraxin occur only in traces

Fraxin, esculin and related coumarins are best known from ash bark, but the leaf contains only traces (0.01% to 0.05%), and one tested sample that contained coumarin derivatives was judged likely adulterated with other ash species or plant parts. The EMA notes these coumarins lack the chemical structure needed for blood-thinning activity.

Clinical trials

1
Ash Leaf Infusions and Inflammatory Mediators in Human Neutrophils (lab study)
PubMed

Phytochemical profiling (UHPLC-DAD-ESI-MS/MS and HPTLC) of ash leaf samples from commercial and natural sources, with in vitro tests of their infusions on human neutrophils. (Kiss et al. 2020, Phytochem Anal)

Isolated human neutrophils in a dish; no people took ash leaf.

The samples contained 64 identified or partly identified compounds, mainly chlorogenic acid, rutin, verbascoside, oleuropein and ligstroside. One sample contained coumarin derivatives, suggesting adulteration with other ash species or plant parts. All infusions inhibited reactive oxygen species, TNF-alpha, IL-8, IL-1 beta and MCP-1 production. Test-tube results only.

2
Compounds Isolated From Ash Leaf Infusion and Human Monocyte Cytokines (lab study)
PubMed

Bio-guided fractionation of an ash leaf infusion and isolation of its main compounds, tested on monocytes and macrophages isolated from the blood of healthy donors. (Kołtun-Jasion et al. 2023, Int J Mol Sci)

Human monocytes and macrophages stimulated with LPS in a dish; the infusion and fractions were tested at 50 micrograms per ml and pure compounds at 20 micromolar.

The infusion and its 20% and 50% methanol fractions lowered TNF-alpha and IL-6 release compared with LPS alone, with no significant effect on IL-1 beta; the infusion and the 50% fraction did not raise IL-10 receptor expression. All six isolated compounds lowered TNF-alpha, and oleuropein, ligstroside, verbascoside and rutin also lowered IL-6; oleuropein and the phenylpropanoids raised IL-10 receptor expression, while formoside and ligstroside did not. One author, Kiss AK, also led the 2020 neutrophil study. Lab results only.

3
Ash Leaf Solvent Extracts and Cytokines in THP-1 Cells (lab study)
PubMed

Isolation of constituents from Fraxinus excelsior leaves and in vitro testing of n-hexane, ethyl acetate and methanol extracts on a human monocytic cell line. (Qasaymeh et al. 2023, J Pharm Pharmacol)

LPS-stimulated THP-1 human monocytic cells in a dish.

Triterpenes, tyrosol esters, pinocembrin and other compounds were isolated. The extracts, ursolic acid, oleanolic acid and pinocembrin significantly reduced TNF-alpha and IL-12, while the tyrosol esters did not. The extracts reduced cell viability with IC50 values of about 40 to 125 micrograms per ml. These solvent extracts differ from a tea. Lab results only.

Side effects and drug interactions

Common Potential side effects

The EU monograph lists no known side effects, but its assessors found no clinical safety data, and the later EU periodic review (adopted 2022) found no adverse reaction reports for ash leaf products.
Not for people who are hypersensitive to ash leaf, or for anyone told to limit fluids, for example because of severe heart or kidney disease, since the traditional use depends on drinking plenty of liquid.
Not recommended under age 18 or during pregnancy or breastfeeding because of a lack of data. Tests for reproductive toxicity, genotoxicity and cancer risk have not been done; lab tests of a narrow-leafed ash leaf extract showed antimutagenic effects in bacteria, which does not replace that testing.
Ash leaf has a folk reputation as a mild laxative, which the EMA links to its high mannitol content, but no such effect has been reported at the monograph doses.
See a doctor if joint pain comes with swelling, redness or fever, or if urinary symptoms worsen or bring fever, painful urination, cramping or blood in the urine.

Important Drug interactions

The EU monograph lists no reported interactions, and none have been studied in people.
Warfarin and other blood thinners: the EMA notes that ash leaf contains only traces of coumarins and that these lack the structure needed for anticoagulant activity; no interaction has been reported, but tell your prescriber about any herbal tea you take.
Prescription diuretics (water pills) and lithium: any added effect on urine flow is theoretical and unstudied; ask the prescriber before combining them.

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Frequently asked questions about Ash Leaf (Fraxinus excelsior)

Is Phytodolor the same as an ash leaf supplement?

No. Phytodolor (STW1) is a combination of aspen leaf and bark, ash bark and goldenrod extracts, so it contains ash bark rather than ash leaf. Pooled trials of the blend in people with musculoskeletal pain favored it over placebo, but those results belong to the three-herb product and say nothing about ash leaf tea or capsules.

How is ash leaf different from ash seed extract?

Ash seed extracts, sold under names such as Glucevia and FraxiPure, are made from the seeds and fruits of the same tree; one contained 6.8% nuzhenide. They were tested, with the maker's staff among the authors, for blood sugar responses, a different use from the leaf's traditional joint and urinary uses. Findings for the seed extract do not apply to the leaf.

Does ash leaf contain the coumarin fraxin?

Only in traces. Fraxin and esculin are best known from ash bark; analyses of the leaf found 0.01% to 0.05% coumarins. In one study, one tested sample that contained coumarin derivatives was judged likely adulterated with other ash species or plant parts, so a coumarin-rich product may not be pure leaf.

Why does ash leaf tea come with advice to drink extra fluid?

Its traditional urinary use is to increase urine flow and flush the urinary tract, which only works with adequate fluid intake, so the EU monograph asks users to drink enough. For the same reason, it rules out ash leaf for anyone told to restrict fluids, for example because of severe heart or kidney disease.

What is Ash Leaf?

Ash leaf is the dried leaf of the European ash (Fraxinus excelsior) or narrow-leafed ash (Fraxinus angustifolia), trees of the olive family. It is taken as a tea or as powdered leaf in capsules.

What is Ash Leaf used for?

NutraSmarts does not list Ash Leaf under a health category. What the research covers: The European Medicines Agency's herbal monograph accepts ash leaf tea as a traditional herbal medicine for relief of minor joint aches.

What is the recommended dosage of Ash Leaf?

No dose has been tested in a human trial of ash leaf alone. EU traditional-use doses for adults: 20 g dried leaf per liter of water as a decoction, or 10 to 30 g per liter as an infusion, split into 2 to 3 doses a day, with plenty of fluid. Always follow the product label and check with a healthcare provider for personal advice.

Is Ash Leaf safe, and does it have side effects?

Side effects and cautions reported for Ash Leaf include: The EU monograph lists no known side effects, but its assessors found no clinical safety data, and the later EU periodic review (adopted 2022) found no adverse reaction reports for ash leaf products. It may also interact with some medications. Ash Leaf is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does Ash Leaf interact with any medications?

Possible interactions include: The EU monograph lists no reported interactions, and none have been studied in people. Warfarin and other blood thinners: the EMA notes that ash leaf contains only traces of coumarins and that these lack the structure needed for anticoagulant activity; no interaction has been rep… If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Ash Leaf?

NutraSmarts rates the evidence for Ash Leaf as Preliminary (1 out of 5). It is backed by 3 study summaries and 14 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(14 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. European Medicines Agency, Committee on Herbal Medicinal Products (HMPC). Community herbal monograph on Fraxinus excelsior L. or Fraxinus angustifolia Vahl, folium (EMA/HMPC/239271/2011). European Medicines Agency. 2012;Final, adopted 27 March 2012. EMA/HMPC/239271/2011..SourceUsed to support: Not PubMed-indexed; official EU monograph. Lists ash leaf only under traditional use, as herbal tea for oral use: relief of minor articular pain, and to increase the amount of urine to flush the urinary tract as an adjuvant in minor urinary complaints, based exclusively on long-standing use. Adult doses: 20 g per 1,000 ml as a decoction or 10 to 30 g per 1,000 ml as an infusion, in 2 to 3 doses daily; see a doctor if symptoms persist beyond 4 weeks (joints) or 2 weeks (urinary). Contraindicated in hypersensitivity and when reduced fluid intake is advised; not recommended under 18 or in pregnancy and lactation; no interactions reported; no undesirable effects known; reproductive toxicity, genotoxicity and carcinogenicity not tested.
  2. European Medicines Agency, Committee on Herbal Medicinal Products (HMPC). Assessment report on Fraxinus excelsior L. or Fraxinus angustifolia Vahl, folium (EMA/HMPC/239269/2011). European Medicines Agency. 2012;Final, 27 March 2012. EMA/HMPC/239269/2011..SourceUsed to support: Not PubMed-indexed; the EMA's scientific review. Describes the leaf constituents (coumarins in traces of 0.01% to 0.05%, secoiridoids, flavonoids about 1.4% with rutin 0.5%, phenolic acids 3.2%, mucilage 15.3%, mannitol 21.0% with a reported range of 16.4% to 28.6%, potassium 1.7%) and Spanish products on the market since 1975. Summarizes limited lab and rat data, including a rat study, reported through a 2007 review, in which an aqueous leaf extract had no effect and an alcoholic extract raised urinary sodium. Reports no clinical pharmacology, efficacy or safety data, so no well-established use; suggests flavonoids, coumarins, iridoids and secoiridoids may explain the joint use and mannitol the mild diuretic and laxative effects; notes the coumarins found lack the structure for anticoagulant activity.
  3. European Medicines Agency, Committee on Herbal Medicinal Products (HMPC). Addendum to Assessment report on Fraxinus excelsior L. or Fraxinus angustifolia Vahl, folium (EMA/HMPC/690227/2021). European Medicines Agency. 2022;Adopted 26 January 2022. EMA/HMPC/690227/2021..SourceUsed to support: Not PubMed-indexed; EU periodic review covering 2010 to 2021. A literature search found 1,455 new references, none judged relevant to the assessment, and no adverse reaction reports for ash leaf products were found in EudraVigilance or the other pharmacovigilance databases checked. The committee decided no revision of the monograph was needed.
  4. Kiss AK, Michalak B, Patyra A, Majdan M. UHPLC-DAD-ESI-MS/MS and HPTLC profiling of ash leaf samples from different commercial and natural sources and their in vitro effects on mediators of inflammation. Phytochem Anal. 2020;31(1):57-67. doi: 10.1002/pca.2866.PubMedUsed to support: Lab study: 64 compounds were identified or partly identified in commercial and wild ash leaf samples, mainly chlorogenic acid, quercetin-3-O-rutinoside (rutin), verbascoside, oleuropein and ligstroside; one sample contained coumarin derivatives, suggesting adulteration with other Fraxinus species or plant parts. All leaf infusions inhibited reactive oxygen species, TNF-alpha, IL-8, IL-1 beta and MCP-1 production by human neutrophils. Not a human study.
  5. Kołtun-Jasion M, Sawulska P, Patyra A, Woźniak M, Dudek MK, Filipek A, Kiss AK. Bio-Guided Isolation of Compounds from Fraxinus excelsior Leaves with Anti-Inflammatory Activity. Int J Mol Sci. 2023;24(4):3750. doi: 10.3390/ijms24043750.PubMedUsed to support: Lab study: an ash leaf infusion and its 20% and 50% methanol fractions (50 micrograms per ml) lowered TNF-alpha and IL-6 release from LPS-stimulated monocytes and macrophages from healthy blood donors, without a significant effect on IL-1 beta. All six isolated compounds (20 micromolar) lowered TNF-alpha; oleuropein, ligstroside, verbascoside and rutin also lowered IL-6, and oleuropein and phenylpropanoids raised IL-10 receptor expression, while the infusion, the 50% fraction, formoside and ligstroside did not. The abstract's summary is broader than these full-text results. Not a human study.
  6. Qasaymeh RM, Rotondo D, Seidel V. Phytochemical study and immunomodulatory activity of Fraxinus excelsior L. J Pharm Pharmacol. 2023;75(1):117-128. doi: 10.1093/jpp/rgac076.PubMedUsed to support: Lab study: triterpenes, tyrosol esters, pinocembrin and other compounds were isolated from Fraxinus excelsior leaves. n-Hexane, ethyl acetate and methanol leaf extracts, ursolic acid, oleanolic acid and pinocembrin significantly reduced TNF-alpha and IL-12 release from LPS-stimulated THP-1 cells; tyrosol esters did not. Not a human study.
  7. Casadebaig J, Jacob M, Cassanas G, Gaudy D, Baylac G, Puech A. Physicochemical and pharmacological properties of spray-dried powders from Fraxinus excelsior leaf extracts. J Ethnopharmacol. 1989;26(2):211-6. doi: 10.1016/0378-8741(89)90069-x.PubMedUsed to support: Rat study of spray-dried powders from aqueous and alcoholic ash leaf extracts; the PubMed record has no abstract and the paper was not read. The EMA assessment report, citing a 2007 review rather than the paper, says the aqueous extract had no effect while the alcoholic extract significantly increased urinary sodium concentration in conscious rats; the Kostova and Iossifova review, also cited by the EMA, describes significant dose-dependent rises in sodium, chloride, potassium and urea excretion with such powders. The secondhand accounts differ. Animal work only.
  8. Kostova I, Iossifova T. Chemical components of Fraxinus species. Fitoterapia. 2007;78(2):85-106. doi: 10.1016/j.fitote.2006.08.002.PubMedUsed to support: Review of the chemistry of the Fraxinus genus up to mid-2004: coumarins, secoiridoids, phenylethanoids, flavonoids and lignans, with reported anti-inflammatory, antimicrobial, antioxidant, liver-protecting and diuretic activities of extracts and constituents. The EMA notes it is not always clear which plant part a given compound came from.
  9. Bouguellid G, Russo C, Lavorgna M, Piscitelli C, Ayouni K, Wilson E, Kim HK, Verpoorte R, Choi YH, Kilani-Atmani D, Atmani D, Isidori M. Antimutagenic, antigenotoxic and antiproliferative activities of Fraxinus angustifolia Vahl. leaves and stem bark extracts and their phytochemical composition. PLoS One. 2020;15(4):e0230690. doi: 10.1371/journal.pone.0230690.PubMedUsed to support: Lab study of narrow-leafed ash leaf and stem bark extracts: ethanol extracts showed moderate to strong antimutagenic (Salmonella test) and antigenotoxic (umu test) effects, and some extracts were selectively toxic to cancer cell lines in a dish. Verbascoside, calceolariosides, oleuropein and ligstroside were identified. Not a human study.
  10. Uehleke B, Brignoli R, Rostock M, Saller R, Melzer J. Phytodolor® in musculoskeletal disorders: re-analysis and meta-analysis. Forsch Komplementmed. 2011;18(5):249-56. doi: 10.1159/000332820.PubMedUsed to support: Reanalysis of raw data from 11 randomized trials of the three-herb product Phytodolor (STW1) in people with musculoskeletal pain: more rated it good or very good than placebo (69.1% vs 48.9%), with no difference in the knee osteoarthritis subgroup and none versus NSAIDs; minor adverse events only. The product uses ash bark, not ash leaf, so none of this applies to ash leaf.
  11. Gundermann KJ, Müller J, Kraft K. STW1 and Its Versatile Pharmacological and Clinical Effects in Rheumatic Disorders: A Comprehensive Report. Evid Based Complement Alternat Med. 2020;2020:7841748. doi: 10.1155/2020/7841748.PubMedUsed to support: Review, partly funded by the maker Steigerwald, with one author its employee: states that STW1 (Phytodolor) is a fixed combination of extracts from aspen leaves and bark (Populus tremula), common ash bark (Fraxinus excelsior) and goldenrod herb (Solidago virgaurea). Cited for the product's composition, showing it does not contain ash leaf.
  12. Visen P, Saraswat B, Visen A, Roller M, Bily A, Mermet C, He K, Bai N, Lemaire B, Lafay S, Ibarra A. Acute effects of Fraxinus excelsior L. seed extract on postprandial glycemia and insulin secretion on healthy volunteers. J Ethnopharmacol. 2009;126(2):226-32. doi: 10.1016/j.jep.2009.08.039.PubMedUsed to support: Double-blind, randomized, placebo-controlled crossover in 16 healthy volunteers: a single 1 g dose of an ash seed extract (FraxiPure, from the maker Naturex; co-authors Roller M and Bily A are listed with Naturex affiliations on the 2014 Glucevia trial) given with 50 g glucose reduced the glycemic area under the curve (P = 0.02), while the insulin area under the curve did not differ from placebo. A seed extract, not ash leaf; cited to separate the two products.
  13. Zulet MA, Navas-Carretero S, Lara y Sánchez D, Abete I, Flanagan J, Issaly N, Fança-Berthon P, Bily A, Roller M, Martinez JA. A Fraxinus excelsior L. seeds/fruits extract benefits glucose homeostasis and adiposity related markers in elderly overweight/obese subjects: a longitudinal, randomized, crossover, double-blind, placebo-controlled nutritional intervention study. Phytomedicine. 2014;21(10):1162-9. doi: 10.1016/j.phymed.2014.04.027.PubMedUsed to support: Randomized, double-blind, placebo-controlled crossover in 22 overweight or obese adults aged 50 to 80 on a mildly reduced-calorie diet, with co-authors from the extract maker Naturex: 1 g a day of an ash seed extract (Glucevia) for 3 weeks lowered the glucose curve in a glucose tolerance test compared with baseline (a within-period change); compared with placebo, it differed in serum fructosamine, plasma glucagon, the adiponectin to leptin ratio and fat mass. A seed extract, not ash leaf; cited to separate the two products.
  14. Flanagan J, Meyer M, Pasamar MA, Ibarra A, Roller M, Alvarez i Genoher N, Leiva S, Gomez-García F, Alcaraz M, Martínez-Carrasco A, Vicente V. Safety evaluation and nutritional composition of a Fraxinus excelsior seed extract, FraxiPure™. Food Chem Toxicol. 2013;53:10-7. doi: 10.1016/j.fct.2012.11.030.PubMedUsed to support: Safety study led by staff of the maker Naturex of an ash seed extract (FraxiPure): oral LD50 above 2,500 mg/kg in rats, and in 100 healthy volunteers 1,000 mg a day for 90 days did not differ from placebo on blood chemistry or blood counts, with similar numbers of mild to moderate adverse events. A seed extract; its safety data do not cover ash leaf tea.