Traditionally used for
- Digestion
Cautions & contraindications
- Bleeding disorders
- Kidney conditions
☯ TCM Properties
Regulates Qi, relieves the Middle Jiao, descends Qi and stops epigastric pain; Kills intestinal parasites
Traditional Chinese Uses
Suo Luo Zi (Fructus/Semen Aesculi) is the seed of the Chinese horse-chestnut or buckeye, Aesculus chinensis. Sweet and warm, entering the Liver and Stomach channels, it is a Qi-regulating herb that spreads constrained Liver Qi and harmonizes the Stomach. It is used chiefly for Liver-Stomach disharmony with Qi stagnation: distending pain of the chest, hypochondrium, epigastrium and abdomen, belching, and poor appetite, and it descends Qi to relieve epigastric pain and fullness.
It is classically noted that a single buckeye seed can ease stubborn epigastric pain, and it is often combined with Qi-movers such as Xiang Fu, Yu Jin or Chuan Lian Zi. Some texts add that it kills intestinal parasites. It is decocted or powdered. Because it is warm and moving, it is used with care where there is marked Yin deficiency with Heat.
Relationships
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Botanical Description
Aesculus chinensis Bunge (Chinese horse-chestnut) is a deciduous tree in the Sapindaceae (formerly Hippocastanaceae), 10-25 m tall, native to northern and central China and traditionally planted around temples and palaces. The trunk has greyish-brown, longitudinally fissured bark and bears a broadly rounded crown. Leaves are opposite, long-petiolate, and palmately compound with 5-7 oblanceolate to obovate leaflets 8-25 cm long, finely serrate at the margins, glabrous and dark green above and somewhat pubescent on the veins beneath. In late spring the tree produces showy upright terminal panicles 20-30 cm long of small whitish flowers with four spreading petals. The fruit is a thick-walled, smooth or warty pyriform capsule 4-6 cm across, splitting at maturity to release one to three large, glossy, chestnut-brown seeds with a pale broad scar ("eye").
Active Constituents
Escin (aescin)
Mixture of barrigenol-type triterpenoid saponinsConcentration: the characteristic and dominant constituent class of the seed; over 300 compounds have been reported from Aesculi semen, with saponins as the principal group
Escin is not a single molecule but a mixture of closely related saponins, chiefly escin Ia, escin Ib, isoescin Ia and isoescin Ib, built on protoaescigenin and related barrigenol aglycones. It is responsible for the anti-oedema, anti-inflammatory and venotonic effects of the drug, and it is equally responsible for its toxicity. Saponins of this class are locally irritant and haemolytic at high concentration, which is why the raw seed is a medicine rather than a food.
Escin Ia
Triterpenoid saponin (beta-escin isomer)Of the four isomers, escin Ia is the most damaging to human proximal tubule (HK-2) cells and binds heat shock protein 70 and 90 with the lowest binding free energy. This makes it the specific constituent behind the renal signal that follows escin exposure.
Protoaescigenin and barrigenol-type aglycones
Triterpene aglyconesThe aglycone backbone of the seed saponins, decorated at C-21, C-22 and C-28 with acetyl, isobutyryl, tigloyl and angeloyl groups. Which acyl groups sit where distinguishes the individual escins and their relative activity.
Aesculin (esculin)
Hydroxycoumarin glucosideConcentration: a characteristic Aesculus metabolite, concentrated in bark and leaf rather than in the seed drug
Aesculin is the second signature pathway of the genus alongside escin, and both pathways were mapped in the Aesculus chinensis genome. Its 6,7-dihydroxycoumarin skeleton is the usual justification given for bleeding-risk cautions around Aesculus preparations, but practitioners should note it belongs primarily to bark and leaf, not to the seed that constitutes Suo Luo Zi.
Alpha-linolenic acid
Polyunsaturated fatty acidIdentified alongside escin Ia as one of the constituents contributing to the anti-inflammatory and hypolipidaemic activity of Aesculus chinensis seed in a growth-stage phytometabolomic study. Seed and leaf were found to have comparable activities but through different compounds.
⚠ Drug Interactions
Nephrotoxic drugs (aminoglycosides, NSAIDs, iodinated contrast media, ciclosporin, tacrolimus)
Adverse renal reactions are a recognised problem in the clinical use of sodium aescinate, the injectable escin salt prepared from the seeds of this same species and of Aesculus wilsonii. Two mechanisms have been characterised: all four escin isomers severely reduce viability of human HK-2 proximal tubule cells by binding the ATP-binding domain of HSP70 and HSP90 and competitively inhibiting heat shock protein function, and sodium aescinate has separately been shown to induce renal toxicity by promoting Nrf2 and GPX4 mediated ferroptosis. Escin is cleared renally, so the tubule sees a high local concentration. The strongest data are for the parenteral purified saponin, and exposure from an oral crude-seed decoction is far lower, but the target organ is the same.
Clinical note: Do not use Suo Luo Zi in established renal impairment, and avoid stacking it with other nephrotoxic agents. If a patient is receiving sodium aescinate injection, treat that as the dose-limiting exposure and do not add the crude herb on top. Check renal function before and during prolonged courses.
Warfarin, direct oral anticoagulants and antiplatelet drugs
Escin is antithrombotic and vasoprotective in its own right, and Aesculus species produce hydroxycoumarins such as aesculin, whose biosynthesis was characterised in the Aesculus chinensis genome. The combination is a standing caution for horse chestnut preparations generally. It rests on this pharmacology and on scattered case reports rather than on any controlled pharmacokinetic or coagulation interaction study with Aesculus chinensis seed, so the strength of the effect is not quantified.
Clinical note: Avoid combining with anticoagulants or dual antiplatelet therapy. If the herb is already in a formula, monitor INR after starting and stop it at least a week before elective surgery.
Horse chestnut seed extract supplements (Aesculus hippocastanum)
The whole modern efficacy literature for oral escin in venous disease, including the Cochrane review of horse chestnut seed extract for chronic venous insufficiency, is built on the European species Aesculus hippocastanum standardised to escin, whereas Suo Luo Zi is the seed of Aesculus chinensis and the Chinese injectable sodium aescinate is made from Aesculus chinensis or Aesculus wilsonii seed. The two are different species delivering the same saponin class, so a patient self-treating varicose veins with a Western horse chestnut supplement while taking a Chinese formula containing Suo Luo Zi is taking escin twice without either practitioner knowing.
Clinical note: Ask directly about horse chestnut, venotonic or venous-health supplements before prescribing Suo Luo Zi, and about sodium aescinate injection in patients recently treated for trauma, post-surgical swelling or cerebral oedema in China.
Hepatotoxic drugs and agents metabolised to reactive intermediates
Sodium aescinate has been shown to induce hepatotoxicity through ATF4, glutathione and GPX4 axis mediated ferroptosis, which is a glutathione-depleting mechanism and therefore additive with other agents that consume hepatic glutathione. As with the renal signal, the evidence is for the concentrated saponin preparation rather than for a crude seed decoction.
Clinical note: Check liver function before prolonged use in patients already on hepatotoxic medication, and treat unexplained transaminase rise on a Suo Luo Zi containing formula as a reason to stop the herb.
Pharmacopoeial substitution among Aesculus species
The Chinese Pharmacopoeia accepts three botanical sources for this drug: Aesculus chinensis Bunge, Aesculus chinensis Bunge var. chekiangensis and Aesculus wilsonii Rehder. They are pooled under one drug name, and escin content also varies with the month of seed collection. A dose that is well tolerated from one batch is therefore not guaranteed to deliver the same saponin load from another.
Clinical note: Treat the dose range conservatively and do not assume equivalence between suppliers. This is a quality-control caution rather than a drug interaction in the usual sense.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 3–9 g | Daily | — | — | 中国药典 2020 monograph 【娑罗子】【用法与用量】3～9g。 【性味与归经】甘，温。归肝、胃经。 — Matched to ChP by romanised drug name (pinyin 'Suo Luo Zi' → 娑罗子); the romanisation is unique across all 649 ChP monographs, and the match was cross-checked against this record's own TCM temperature. Quoted verbatim. |
Evidence Tier
Strong evidence · 5 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
1
0 verified · 1 unverified
Show the study
Randomized controlled trial
1
0 verified · 1 unverified
Other clinical trial
0
Observational / case report
0
In vitro / animal
3
0 verified · 3 unverified
Show 3 studies
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
Clinical efficacy of sodium aescinate administration following endovenous laser ablation for varicose veins
Eighty-seven patients with CEAP class C2 to C5 varicose veins undergoing endovenous laser ablation with phlebectomy or foam sclerotherapy were randomised to sodium aescinate 60 mg twice daily for 20 days or to no venoactive drug. Calf and ankle circumference recovered significantly faster in the treated group at days 10, 21 and 30. The intervention is the purified saponin salt prepared from Aesculus chinensis and Aesculus wilsonii seed, not the crude Suo Luo Zi decoction, and the control arm received no placebo, so the trial supports the constituent rather than the herb as dispensed.
Horse chestnut seed extract for chronic venous insufficiency
A Cochrane review of randomised trials of oral horse chestnut seed extract mono-preparations against placebo or reference therapy in chronic venous insufficiency, finding an improvement in leg pain, oedema and pruritus relative to placebo. The species throughout is the European Aesculus hippocastanum standardised to escin, not Aesculus chinensis. It is included here because it is the evidence base practitioners are most likely to invoke for Suo Luo Zi, and the substitution of one Aesculus species for another should be made knowingly rather than silently.
Computational and experimental characterization of isomers of escin-induced renal cytotoxicity by inhibiting heat shock proteins
All four isomeric escins, the beta forms escin Ia and Ib and the alpha forms isoescin Ia and Ib, severely reduced viability of human HK-2 kidney cells. Beta-glucuronidase hydrolysis of sodium aescinate reduced the cytotoxicity, implicating the intact glycosides. Sodium aescinate concentration-dependently suppressed heat shock protein expression in MDCK cells, and docking and molecular dynamics showed the escins bind the ATP-binding domain of HSP70 and HSP90, with escin Ia binding most tightly and being most cytotoxic. This gives a defined molecular mechanism for the renal adverse reactions reported clinically with escin.
Sodium aescinate induces renal toxicity by promoting Nrf2/GPX4-mediated ferroptosis
Sodium aescinate produced renal injury through ferroptosis mediated by the Nrf2 and GPX4 axis. Together with the heat shock protein work this establishes two independent mechanisms of escin nephrotoxicity, both of which act on the renal tubule and both of which argue against combining escin-containing preparations with other agents that stress the same cells.
Sodium aescinate-induced hepatotoxicity via ATF4/GSH/GPX4 axis-mediated ferroptosis
Sodium aescinate caused hepatocellular injury via ferroptosis driven by the ATF4, glutathione and GPX4 axis. The finding extends the toxicity of the escin fraction beyond the kidney to the liver and identifies glutathione depletion as the shared pathway, which is the basis for caution when the drug is combined with other glutathione-consuming agents.
⚠ Safety & Contraindications
- Bleeding disorders
- Kidney conditions
Contraindications
Its use is prohibited in patients with qi deficiency and yin deficiency.
Source: Xi S, Gong Y. Essentials of Chinese Materia Medica and Medical Formulas. Academic Press/Elsevier, 2017, pp. 171–182.
Historical Texts
Ben Cao Gang Mu
Ming dynasty, 1596References
- Wang A, Xia Y, Wang H, Chang H, Luo D, Wu S, Lv H, Zhao N, Wang F. Aesculi semen (Aesculus chinensis Bunge and Aesculus wilsonii Rehd): A review of its phytochemistry, pharmacology, clinical application and toxicity . Fitoterapia (2025) [DOI]
- Wang Y, Han X, Wan X, Niu F, Zhou C. β-Escin: An Updated Review of Its Analysis, Pharmacology, Pharmacokinetics, and Toxicity . The American Journal of Chinese Medicine (2023) [DOI]
- Gallelli L. Escin: a review of its anti-edematous, anti-inflammatory, and venotonic properties . Drug Design, Development and Therapy (2019) [DOI]
- Sun W, Yin Q, Wan H, Gao R, Xiong C, Xie C, Meng X, Mi Y, Wang X, Wang C, et al.. Characterization of the horse chestnut genome reveals the evolution of aescin and aesculin biosynthesis . Nature Communications (2023) [DOI]
- Liu Y, Ren D, Liu Y, Li N, Jiang X, Zhang Y, Liu R. Comprehensive Evaluation of Growth Period Variations in Bioactive Properties and Phytochemical Profiles of Aesculus chinensis Bge Seeds and Leaves . Biomedical Chromatography (2026) [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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