Yuan Zhi
StarPolygala tenuifolia Willd.
Traditionally used for
- Cough & breathing
- Sleep
- Mood & calm
- Heart & circulation
☯ TCM Properties
Calms the Spirit and Benefits Intelligence; Expels Phlegm and Opens the Orifices; Promotes Heart-Kidney Communication; Disperses Swelling and Dissipates Abscesses
Traditional Chinese Uses
Yuan Zhi (polygala root) is a warm herb that calms the Spirit, opens the Heart-orifices, transforms Phlegm, and opens the Lung. It is used for anxiety, insomnia, palpitations, and disturbed dreams from disturbance of the Heart-Shen by Phlegm — particularly when emotional upset, over-thinking, or worry is involved. Its Phlegm-resolving action also benefits cough with abundant phlegm, carbuncles, and swellings. As a herb that bridges the Heart and Kidney, it facilitates communication between the two organs in formulas for Kidney-Heart disharmony.
Western Herbalism Properties
Used In Formulas (5)
Relationships
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Botanical Description
Polygala tenuifolia, the thinleaf milkwort, is a slender perennial herbaceous plant in the family Polygalaceae, native to dry, sunny grassland slopes, gravelly hillsides, and pine forests across northern China, Mongolia, Korea, and the Russian Far East. It grows from a long, cylindrical, slightly twisted, pale-yellow taproot with a wrinkled, somewhat spongy cortex that is easily separated from the woody central core. Multiple erect or ascending stems 15-40 cm tall rise from the crown, bearing numerous alternate, linear to narrowly oblanceolate leaves 1-3 cm long with entire margins. Small purple to bluish-violet papilionaceous flowers, each with three petals and two petaloid sepals (wings), are borne in slender terminal racemes. The fruit is a small, flattened, oblong capsule containing two seeds with white arils.
Active Constituents
Onjisaponin B
Oleanane-type triterpenoid saponin (presenegenin glycoside)Concentration: One of more than 50 saponins reported from the root; total root saponin content has been reported at roughly 1.5-3.3%
Onjisaponin B carries the most sugar residues of the commonly studied Polygala saponins and is both the most sedative and the most irritant. In mice it increased the number of animals falling asleep and prolonged pentobarbital sleeping time, altered the amplitude and frequency of isolated jejunum contractions at 20-80 mg/L, and significantly lowered gastric PGE2, meaning loss of mucosal prostaglandin protection. Sedative potency and gastrointestinal toxicity track together across the saponin series (onjisaponin B greater than tenuifolin greater than senegenin), so they cannot be separated by simply choosing a different saponin.
Tenuifolin
Triterpenoid saponin (partially deglycosylated presenegenin derivative)Concentration: A Chinese Pharmacopoeia quality index for the root, reported as required at not less than 2.0%
Tenuifolin is the main deglycosylated saponin and the usual assay marker. It is sedative in the pentobarbital sleep model and inhibits acetylcholinesterase and beta-secretase in vitro, which is the pharmacological basis for the drug's cognitive claims. It still lowers gastric PGE2, so it is less irritant than onjisaponin B but not innocuous.
Senegenin
Triterpenoid sapogenin (aglycone)The fully deglycosylated aglycone. In the comparative mouse study it was neither sedative nor a stimulant of jejunal motility, although it still reduced gastric PGE2. It is the endpoint of the sugar-chain cleavage that processing is thought to accomplish, which is why processing lowers toxicity and activity together.
3,6'-Disinapoyl sucrose
Oligosaccharide ester (sucrose ester)Concentration: A Chinese Pharmacopoeia quality-control marker for the root
The best studied of the more than 30 oligosaccharide esters unique to the Polygalaceae. It shows antidepressant-like and neuroprotective activity in rodent models and, unlike the saponins, is not associated with gastric irritation, so it is the fraction most often proposed for isolated development.
Tenuifolisides
Oligosaccharide esters (sucrose esters)A family of sucrose esters acylated with sinapoyl and related groups, reported alongside 3,6'-disinapoyl sucrose and contributing to the neuroprotective profile of the aqueous extract.
Polygalaxanthone III
Xanthone C-glycosideConcentration: A Chinese Pharmacopoeia quality-control index for the root
The marker xanthone of more than 40 reported from the root. Xanthones contribute antioxidant and monoamine-related activity in vitro; their contribution at clinical doses is not established.
Harman and norharman
Beta-carboline alkaloidsTrace beta-carbolines reported in the root. Beta-carbolines are reversible MAO-A inhibitors in vitro, and their presence, though at low levels, is the only concrete basis for caution about combining the root with serotonergic drugs.
⚠ Drug Interactions
NSAIDs, aspirin and corticosteroids
Polygala saponins are directly irritant to the gastric mucosa and act by the same final pathway as NSAIDs. In mice, onjisaponin B, tenuifolin and senegenin all significantly reduced gastric PGE2, and onjisaponin B at 200 mg/kg did so markedly; reviews of Polygalae Radix attribute its documented gastrointestinal toxicity to the saponins and note gastrointestinal motility disorder, flatulence and thinning of the intestinal wall on long or high-dose use. Prostaglandin depletion by the herb plus COX inhibition by an NSAID is straightforwardly additive.
Clinical note: Avoid the raw root in patients on regular NSAIDs, aspirin or corticosteroids, and in anyone with active or recent peptic ulcer, gastritis or reflux. If the herb is needed, use the honey-processed or licorice-processed form, keep the dose at the low end, give it after food, and stop on any epigastric pain or nausea.
Raw (sheng) versus processed (zhi) Yuan Zhi
Processing works by cleaving sugar residues from the saponins. The comparative mouse study showed both sedative activity and gastrointestinal irritancy falling in the order onjisaponin B, tenuifolin, senegenin, that is, in step with decreasing glycosylation, and reviews record that co-decoction with licorice at 3:2 or 3:3 ratios prevented saponin toxicity. Raw and processed Yuan Zhi are therefore not interchangeable at equal weight, in either direction: the processed root is better tolerated and correspondingly less sedative.
Clinical note: State raw or processed on the prescription. Use honey- or licorice-processed root for oral internal use, especially in the elderly and in anyone with a sensitive stomach; reserve the raw root for external use or short courses in robust patients.
Benzodiazepines, Z-drugs and other CNS depressants
Onjisaponin B and tenuifolin both significantly increased the proportion of mice falling asleep and prolonged sleeping time in hypnotic and subhypnotic pentobarbital models. The root has been used as a sedative for centuries and its saponins demonstrably potentiate a barbiturate, so additive effect with prescribed hypnotics is expected.
Clinical note: Ask about hypnotics and sedating antihistamines before prescribing, and warn about driving in the first days of treatment.
Injectable or intravenous use of Polygala saponin preparations
Triterpenoid saponins of this class are surface-active and lyse erythrocyte membranes; haemolytic activity is a defining property of the saponin fraction and is the standard reason saponin-rich drugs are restricted to the oral or topical route. This is a route-of-administration hazard, not a decoction hazard.
Clinical note: Oral and external use only. Never compound Yuan Zhi or its saponin fractions for injection.
MAO inhibitors and serotonergic antidepressants
Harman and norharman, reversible MAO-A inhibitors in vitro, are reported as trace alkaloids of the root, and the oligosaccharide esters show antidepressant-like activity in rodent models. No pharmacokinetic or clinical interaction study exists and the alkaloid levels are very low, so this is a precaution rather than a documented interaction.
Clinical note: No routine restriction. Mention it if a patient on an MAOI or high-dose SSRI reports new agitation, and review the whole formula rather than blaming this herb alone.
Other Polygala species substituted for Polygala tenuifolia
Polygalae Radix is a genus-level trade item and reviews of the drug report saponin content varying with the species supplied. Because gastric irritancy tracks the degree of saponin glycosylation, material from a different Polygala species can be markedly more or less irritant than Polygala tenuifolia at the same weight.
Clinical note: Source root that is identified to species and assayed for tenuifolin, and treat an unexpected episode of nausea or epigastric pain as a possible material problem, not only a dose problem.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 3–10 g | Daily | — | — | 中国药典 2020 【用法与用量】3～10g。 【性味与归经】苦、辛，温。归心、肾、肺经。 — Chinese Pharmacopoeia 2020, quoted verbatim; route and cautions preserved. Replaces a cleared category-filler value. |
Dui Yao — Herb Pairs
The classical two-herb combinations this herb appears in, each with an action neither herb has alone.
Opens the orifices and transforms phlegm while connecting heart and kidney, calming the spirit and improving memory.
Forgetfulness, palpitations and insomnia with phlegm misting the heart; also in Kong Sheng Zhen Zhong Dan (Qian Jin Yao Fang).
Named pairing — Lü Jingshan, Shi Jinmo Dui Yao
Evidence Tier
Strong evidence · 4 studiesRecorded studies by study design, strongest design at the top. This is a study-design tier only, not a GRADE rating: it does not weigh risk of bias, consistency or precision.
Systematic review / meta-analysis
0
Randomized controlled trial
3
3 verified · 0 unverified
Other clinical trial
0
Observational / case report
0
In vitro / animal
1
0 verified · 1 unverified
Other / unclassified
0
Verified: design read from PubMed for a DOI that resolves to the cited paper Unverified: taken from the study's recorded description
Clinical Studies
BT-11 is effective for enhancing cognitive functions in the elderly humans
Randomised, double-blind, placebo-controlled trial of BT-11, an extract of Polygala tenuifolia root, in elderly participants (28 treated, 25 placebo), assessed with the CERAD battery and the MMSE. Total CERAD scores rose significantly more on BT-11 than placebo, with word list recognition, constructional recall and praxis, and the modified Boston naming test improved. The trial is small, short and industry-linked, and reports no safety data, so it supports a signal rather than a clinical recommendation.
Effects of BT-11 on memory in healthy humans
Randomised, double-blind, placebo-controlled parallel-group trial of BT-11 capsules three times daily for four weeks in healthy adults, using the Korean California Verbal Learning Test and the Self-Ordered Pointing Test. BT-11 produced greater gains in immediate recall than placebo, improved K-CVLT recognition where placebo did not, and reduced errors on the working-memory task. Most K-CVLT subtests improved in both arms, showing a substantial practice effect that limits how much weight the between-group differences carry.
Study on the safety of Polygala tenuifolia Willdenow root extract powder (BT-11) in young person aged from 9 to 19 years old
Randomised safety study of BT-11 300 mg daily versus matching placebo for 12 weeks in 121 subjects aged 9 to 19 (61 active, 60 placebo), with haematology, blood chemistry, urinalysis, vital signs, weight and ECG. Eleven adverse reactions occurred in ten BT-11 subjects and seven in six placebo subjects, with no significant difference in incidence and no difference in laboratory tests, vital signs or ECG; the two serious events (acute appendicitis and acute viral gastroenteritis) were judged unrelated. Note that this tests a standardised extract at a modest fixed dose, not a raw-root decoction, so it does not license the raw drug in children.
The Gastrointestinal Irritation of Polygala Saponins and Its Potential Mechanism In Vitro and In Vivo
Compared onjisaponin B, tenuifolin and senegenin, which differ in glycosylation, using pentobarbital sleep tests, isolated jejunum motility and gastric PGE2 and intestinal TNF-alpha in mice. Onjisaponin B and tenuifolin, but not senegenin, increased sleeping and altered jejunal contraction amplitude and frequency; all three significantly reduced gastric PGE2 without clearly affecting intestinal TNF-alpha. Both sedative potency and gastrointestinal irritancy fell in the order onjisaponin B, tenuifolin, senegenin, supporting the view that traditional processing reduces toxicity by cleaving sugars, at the cost of also reducing activity.
Historical Texts
Shen Nong Ben Cao Jing
Han dynastyMing Yi Bie Lu
Southern and Northern dynastiesBen Cao Gang Mu
Ming dynastyReferences
- Liu M, Wang X, Gao D. Polygalae Radix: review of metabolites, pharmacological activities and toxicology . Frontiers in Pharmacology (2024) [DOI]
- Park CH, Choi SH, Koo JW, Seo JH, Kim HS, Jeong SJ, Suh YH. Novel cognitive improving and neuroprotective activities of Polygala tenuifolia Willdenow extract, BT-11 . Journal of Neuroscience Research (2002) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
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