Polygala tenuifolia (Yuan Zhi)
Summary
Polygala tenuifolia root (yuan zhi) is a traditional East Asian herb. Two small 2009 trials of its extract BT-11 reported better memory scores in healthy adults and in 53 older adults. A 121-person trial in young people found 300 mg/day for 12 weeks as safe as placebo. All human data involve one extract.
Key facts
- Dried root of Polygala tenuifolia; BT-11 is a root extract that inhibited acetylcholinesterase in lab studies[1][2]
- Total CERAD scores rose more with BT-11 (28 people) than placebo (25), especially word-list recognition and naming[1]
- BT-11 three times daily for 4 weeks improved immediate verbal recall and working-memory errors vs placebo[2]
- 300 mg/day for 12 weeks in 121 people aged 9–19: adverse reactions and lab tests similar to placebo[3]
- 2 graded human outcomes on this page
- October 13, 2026
How it works
ProposedBT-11 inhibited acetylcholinesterase in vitro and improved memory in rats, so it is proposed to raise brain acetylcholine. This has not been measured in people.[1][2]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Safety | Grade D | No effect | RCT · n = 121 · 2019 | 1 row |
| Memory | Grade D | Improved | RCT · n = 53 · 2009 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Adverse reactions and safety labs in young people | No effect | Grade D | RCT · n = 121 · 2019 Young people aged 9–19 Form: BT-11 root extract powder · Dose: 300 mg/day · Duration: 12 weeks Adverse reactions (11 in 10 people vs 7 in 6 on placebo), labs, vital signs and ECG did not differ; serious events were judged unrelated. | 30576772 (opens PubMed)Source [3] |
| Memory and cognition in older adults | Improved | Grade D | RCT · n = 53 · 2009 Older adults Form: BT-11 Polygala tenuifolia root extract · Dose: Dose not stated in the abstract · Duration: Not stated in the abstract Total CERAD scores improved more with BT-11 than placebo, notably word-list recognition, constructional recall and praxis, and modified Boston naming. | 19699261 (opens PubMed)Source [1] |
Forms
Studied doses
Doses studied in human trials ranged from 300 mg/day for 12 weeks (adolescent safety trial); the memory trials gave BT-11 three times daily but do not state the dose in their abstracts.[3][2][1]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- Cholinergic and anticholinergic drugsRCTBT-11 inhibited acetylcholinesterase in lab studies, the same action as donepezil-type drugs, so effects could add to them or oppose anticholinergic drugs. Not studied in people.[2]
Who should be careful
- People on dementia medicines
- Lab data suggest the same mechanism as acetylcholinesterase inhibitors; combined use is untested.[2]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
How to read the label
Frequently asked questions
Does Polygala tenuifolia improve memory?
Two small trials of the extract BT-11 reported better memory test scores in healthy and older adults; neither has been independently replicated.[1][2]
Is Polygala tenuifolia safe?
A 12-week trial of 300 mg/day in 121 young people found safety measures similar to placebo.[3]
How might it work?
In lab studies BT-11 blocked acetylcholinesterase, the enzyme targeted by some dementia drugs.[2]
Is yuan zhi the same as BT-11?
Yuan zhi is the root; BT-11 is a specific extract of it, and only BT-11 has human trials.[1]
Sources
- [1]BT-11 is effective for enhancing cognitive functions in the elderly humans.. Neurosci Lett, 2009. RCT
- [2]Effects of BT-11 on memory in healthy humans.. Neurosci Lett, 2009. RCT
- [3]Study on the safety of Polygala tenuifolia Willdenow root extract powder (BT-11) in young person aged from 9 to 19 years old.. J Ethnopharmacol, 2019. RCT
What changed
- First draft. Every PMID checked against NCBI E-utilities esummary (title and year taken from the record) and abstracts read for the cited rows.
- Self-review pass (strict second read): undisclosed doses marked as such; 2009 healthy-adult trial kept out of the evidence table (no participant count in abstract). Drug interactions checked explicitly: cholinergic/anticholinergic drugs (listed, lab mechanism); anticoagulants, diabetes and blood-pressure drugs, antibiotics, levodopa, chemotherapy (no data, stated).