Ashwagandha withanolides found in human urine after oral doses
What it found
After older adults took a commercial ashwagandha extract, four withanolides showed up in their urine over 12 hours.
Three were identified, and one was an unknown compound not present in the extract itself.
What they found
Studies in people
Four withanolides in urine
Withaferin A, sominone, 3R-viscosalactone B and an unidentified compound called WFNX were detected in participant urine. The other seven withanolides tested for were not found at either dose.
Highest amount excreted
3R-viscosalactone B was excreted in the largest amounts, ranging from 0.34 to 0.73 micromoles at the 240 mg dose and 1.11 to 1.90 micromoles at the 480 mg dose.
Low recovery overall
Only a small percentage of the administered withanolides appeared in urine. Recovery was 0.83 to 2.08 percent for 2,3-didehydrosomnifericin/3R-viscosalactone B and 0.16 to 1.84 percent for withaferin A.
Sominone mostly conjugated
Sominone was not detectable in urine without first treating the samples with enzymes, showing it is mostly excreted in a conjugated form. The percentage of administered sominone excreted was much higher than for the other compounds, at 19 to 58 percent.
Unknown metabolite WFNX
WFNX was abundant in all participant urine samples but was not found in the Shoden powder. It appears to be a structural isomer of 4-oxo withaferin A, and the authors could not determine its structure.
Variation between people
The amounts excreted varied considerably between participants at the same dose. For example, at 480 mg, withaferin A excretion ranged from 0.05 to 0.79 micromoles across three participants.
What the authors conclude
“To our knowledge, these are the first data confirming the urinary excretion of withanolides from WS in humans.”
Also in their conclusions
- They say these results provide new insights into the oral absorption, metabolism and urinary excretion of withanolides from ashwagandha.
- They advise that future human pharmacokinetic studies of ashwagandha products should analyze additional withanolide metabolites and conduct untargeted analyses to capture the full range of compounds present in the body after oral ingestion.
- They note that withaferin A may undergo extensive biotransformation in the body, which would affect observed plasma and urine concentrations.
How it was done
Human studies have measured withanolides in blood after taking ashwagandha, but none had looked at how these compounds leave the body in urine. The authors wanted to fill that gap to better understand absorption, metabolism and excretion.
Four healthy older adults (average age 71.3 years) took single oral doses of 240 mg or 480 mg of Shoden, a commercial ashwagandha root and leaf extract. Urine was collected for 12 hours afterward and analysed for 11 withanolides using a validated lab method.
What it can’t tell you
- The study was small, with only four participants, and only one completed both dose visits, so the results may not reflect what happens in larger or different groups.
- The amounts of WFNX and 3R-viscosalactone B excreted may differ from the true values because they were measured using calibration curves for other compounds.
- This study measured how much of each compound appeared in urine over 12 hours. It cannot show whether these compounds have any health effect in people.
Who paid
- Funding
- Funded by NCCIH NIH HHS; NIA NIH HHS; NCATS NIH HHS; NIGMS NIH HHS; Office of Dietary Supplements; ODCDC CDC HHS (from the PubMed record).
- Conflicts
- The authors declare no conflicts of interest.
- Authors work at
- Oregon Health & Science University (OHSU), USA; Portland State University (PSU), USA; Oregon State University, USA
The paper
- Title
- Withanolides Are Detected in Human Urine Following Oral Administration of a Withania somnifera Product
- Type
- Study
- Evidence
- Studies in people
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Speers AB, Limoico ED, Lozano-Ortiz A, et al (2026). Withanolides Are Detected in Human Urine Following Oral Administration of a Withania somnifera Product. International journal of molecular sciences. doi:10.3390/ijms27125289Free full textPubMed 42353009DOI
Summary written 29 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error