Urolithin D
Urolithin D is the least-characterized but, in cell-based studies, the most potently antioxidant member of the urolithin family — compounds produced by gut bacteria from ellagitannins found in pomegranates, walnuts, and other foods.
Number of studies
3
Safety
High
Time to effects
No data — all available observations come from in vitro tests, without animal or human studies that would allow assessment of timing in a living organism.
Who it's for
Table of contents
TL;DR
Urolithin D is the least-characterized but, in cell-based studies, the most potently antioxidant member of the urolithin family — compounds produced by gut bacteria from ellagitannins found in pomegranates, walnuts, and other foods.
- →Showed one of the strongest antioxidant activities among the urolithins tested in comparative in vitro assays
- →Supported repair of oxidative DNA damage in cell-based studies
- →Selectively inhibited EphA2 receptor phosphorylation in prostate cancer cell lines under in vitro conditions
| Compound family | Urolithins — metabolites of ellagitannins and ellagic acid produced by gut microbiota |
|---|---|
| Relationship to urolithin A | A distinct, far less studied molecule from the same metabolic family |
| Research level | Hypothesis-stage / very early — in vitro studies only, no animal or human studies |
| Distinguishing feature | One of the strongest antioxidants among urolithins in comparative tests (low IC50 value) |
| Studied mechanism | Free-radical neutralization, repair of oxidative DNA damage, selective EphA2 receptor inhibition in vitro |
| Precursor sources | Pomegranates, walnuts, certain berries (plants rich in ellagitannins) |
Understand
Overview
Urolithin D is one of the metabolites in the urolithin family — compounds formed in the colon from ellagitannins and ellagic acid, present in foods such as pomegranates, walnuts, and certain berries. Unlike the well-characterized urolithin A (studied mainly in the context of mitophagy and muscle health), urolithin D remains one of the least-characterized members of this family — far fewer publications address it directly, and most of those cover single, narrowly scoped cell-based experiments.
Researchers' interest in urolithin D stems mainly from one recurring observation: in comparative tests of antioxidant activity across different urolithins, urolithin D consistently emerges as one of the strongest, with a lower IC50 value (i.e., greater potency at neutralizing free radicals) than ellagic acid, its own precursor. This has led a handful of research groups to look more closely at it — including its ability to repair oxidative DNA damage and to selectively inhibit specific cell receptors linked to cancer progression.
It should be stated plainly that this is a very early-stage basic-science topic. Available data comes exclusively from in vitro studies (chemical assays and cell lines) — there are no animal studies, let alone human studies, that would allow assessment of whether the antioxidant and anticancer properties observed in a test tube have any translation to a living organism.
Mechanism of action
Like the other urolithins, urolithin D forms in the colon through a multi-step breakdown of ellagic acid by gut bacteria capable of this conversion (including genera such as Gordonibacter and Ellagibacter). Whether and how much urolithin D a given person produces depends on their individual gut microbiota composition — a phenomenon described as urolithin metabotype.
In chemical and cell-based assays, urolithin D neutralizes free radicals through several parallel antioxidant mechanisms (including hydrogen-atom and electron transfer), while also showing the ability to cyclically regenerate its antioxidant activity and to repair oxidative DNA damage (including 8-oxoguanine-type lesions). In separate cell-based studies on prostate cancer lines, urolithin D selectively inhibited phosphorylation of the EphA2 receptor — a protein involved in the progression of certain cancers — more strongly and selectively than the other urolithins tested. All these observations, however, come from isolated cell systems or cell-free chemical assays, without confirmation in living organisms.
Intake of plant precursors
Dietary ellagitannins and ellagic acid reach the colon undigested.
Conversion by gut microbiota
Gut bacteria capable of this conversion break down ellagic acid, producing among other things urolithin D — in smaller amounts than other urolithins in some people.
Antioxidant activity in vitro
In chemical and cell-based assays, urolithin D neutralizes free radicals and supports repair of oxidative DNA damage.
Evidence: limited — based on 3 studies in this database.
Benefits
Common myths
MythSince urolithin D is the strongest antioxidant in test-tube assays, it's the most valuable urolithin for health.
FactThe strength of antioxidant activity in an isolated chemical or cell-based assay doesn't automatically translate into health benefits in a living organism — without animal and human studies, the real-world significance of this property can't be assessed.
MythUrolithin D is simply a 'version' of urolithin A with a different number.
FactIt's a distinct molecule with a different chemical structure and a far smaller body of research — its only direct connection to urolithin A is a shared origin in the same ellagic-acid metabolic pathway.
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Practice
Frequently asked questions
No — at this stage of research, urolithin D is not the subject of any human clinical trials, nor is it an available, clinically tested supplement. Any such products on the market currently lack backing from clinical studies.
Most earlier urolithin research focused on urolithin A because of its link to mitophagy and muscle health. Urolithin D only drew attention during broader, comparative screening studies of the entire urolithin family for antioxidant and anticancer activity.
In theory yes, since pomegranates are a source of precursors (ellagitannins), but the amount of urolithin D actually produced depends heavily on an individual's gut microbiota composition — there's no guarantee this would translate into a detectable rise in blood levels.
Safety
Side effects & contraindications
Possible side effects
Contraindications
No significant contraindications at typical doses.
Is it worth taking?
Who it's for
- People following very early basic research on the urolithin family and plant polyphenols
- People interested in cellular oxidative-stress mechanisms
Not for
- No significant contraindications at typical doses.
Evidence
Worth knowing
In comparative studies, urolithin D had a lower (better) IC50 value in antioxidant assays than ellagic acid, the compound it's derived from.
The number of scientific publications devoted directly to urolithin D is far smaller than for urolithin A or even urolithin C.
Studies
Urolithins, intestinal microbial metabolites of pomegranate ellagitannins, exhibit potent antioxidant activity in a cell-based assay
Research hypothesisKasimsetty SG, Bialonska D, Reddy MK, Thornton C, Willett KL, Ferreira D · Journal of Agricultural and Food Chemistry · 2009
A cell-based study comparing the antioxidant activity of urolithins A, B, C, and D and ellagic acid — urolithin D showed one of the strongest antioxidant activities in this comparison.
View studyThe ellagitannin colonic metabolite urolithin D selectively inhibits EphA2 phosphorylation in prostate cancer cells
Research hypothesisGiorgio C, Mena P, Del Rio D, Brighenti F, et al. · Molecular Nutrition & Food Research · 2015
An in vitro study on prostate cancer cell lines showing that urolithin D selectively inhibits EphA2 receptor phosphorylation more strongly than the other urolithins tested — a cell-level study only.
View studyUrolithin D: A promising metabolite of ellagitannin in combatting oxidative stress
Research hypothesisMilanović Ž, et al. · Chemico-Biological Interactions · 2025
A paper analyzing the chemical mechanisms by which urolithin D neutralizes free radicals and repairs oxidative DNA damage — a theoretical and in vitro analysis, without data from living organisms.
View studySources & bibliography
Citations are illustrative for this demo version and require full bibliographic verification by the editorial team before production publication.
Compare with similar entries
About the authors of this entry
Author
dr Anna KowalczykEditor-in-Chief, Molecular Biology
Anna studied molecular biology at the University of Warsaw, then spent eight years after her PhD in a lab researching the mechanisms of cellular aging and autophagy. She stumbled into science journalism almost by accident — frustrated by how easily her field's findings get oversimplified in the media, she started a blog explaining the biology of aging in plain language. That blog became the seed of VitMode. Today Anna oversees the entire editorial process, holding every piece to the same rigor her old lab demanded: primary sources, methodology checks, and honesty about the limits of the evidence. Outside work, she's a dedicated boulderer.
121 publications on this site
Medical review
dr Piotr ZielińskiEndocrinologist
Piotr has practiced endocrinology for more than fifteen years, mostly in male hormonal disorders and metabolic health. He joined VitMode as a scientific consultant because, as he jokes, he got tired of explaining the same testosterone questions at every appointment and decided to write the answers down properly, once. He reviews content on hormone therapy, supplement pharmacology and drug interactions, making sure articles never turn into encouragement to self-supplement in situations that genuinely need diagnostics and medical supervision. His professional motto — "evidence first, enthusiasm second" — has come up more than once with a patient who arrived with a supplement plan they found online.
174 publications on this site
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Comments (2)
- KW
Kasia W. 2 weeks ago
Very clearly explained, especially the interactions section — I hadn't seen it laid out this well anywhere else.
- MT
Marek T. a month ago
Are you planning to update this with the newest study from this year? I saw an interesting meta-analysis.