Hai Tong Pi
StarErythrina variegata L. var. orientalis (L.) Merr.
Traditionally used for
- Pain & joints
- Skin
☯ TCM Properties
Dispels Wind-Dampness; Unblocks the Channels and Collaterals; Alleviates Pain; Kills Parasites and Stops Itching
Traditional Chinese Uses
Hai Tong Pi (erythrina bark, coral bean bark) is a bitter, pungent, neutral herb used in Chinese medicine to expel Wind-Damp from the channels and collaterals, relieving joint pain and stiffness. It addresses bi syndrome affecting the knees and lower back with swelling and restricted movement. Its anthelmintic properties are applied for intestinal parasites, and topically it treats skin conditions including eczema and pruritus from Wind-Damp.
Relationships
Full-screen graph →Click a node for details · double-click to expand it · Ctrl/⌘ + scroll or two fingers to zoom and pan.
Botanical Description
Erythrina variegata, the Indian coral tree or tiger's-claw, is a medium-sized deciduous tree of the family Fabaceae native to coastal forests of tropical Asia, Polynesia and northern Australia, reaching 15-20 m in height with a stout trunk armed with short, conical, black prickles and a spreading crown. The trifoliolate leaves have broadly rhombic to ovate leaflets 8-20 cm long, the terminal leaflet the largest, glabrous and bright green. The tree flowers when leafless in the dry season, producing dense terminal racemes of brilliant scarlet, papilionaceous flowers 5-8 cm long whose large standard petal gives the inflorescence a flame-like appearance. The fruit is a cylindrical, constricted pod 15-30 cm long, containing several dark red, kidney-shaped seeds. The medicinal bark is greyish-brown, fissured and prickled, with a slightly bitter, acrid taste.
Active Constituents
Erysotrine
Erythrinane (Erythrina) alkaloidConcentration: Reported as a principal alkaloid of Erythrina variegata; the alkaloid fraction of the bark is small compared with that of the seed
An aromatic erythrinane alkaloid, one of the class that gives the genus its pharmacological identity. The Erythrina alkaloids act at nicotinic acetylcholine receptors and are the basis of the classical curare-like reputation of the genus. Note that this alkaloid was characterised from the plant as a whole; the medicinal drug Hai Tong Pi is the bark, and the seed is much the richer and more hazardous alkaloid source.
Erysodine
Erythrinane (Erythrina) alkaloidConcentration: A recurrent alkaloid of Erythrina species, reported from Erythrina variegata alongside erysotrine
A competitive antagonist at neuronal nicotinic acetylcholine receptors with high affinity for the alpha4beta2 subtype, characterised in radioligand and functional assays and shown in rodents to reduce nicotine-related and ethanol-drinking behaviour. This is receptor-level pharmacology on the neuronal, not the muscle-type, nicotinic receptor, and it is the best-defined mechanism attributable to any single alkaloid of this plant.
Erythraline and related erythrinane alkaloids (erysovine, erysopine, erythratine)
Erythrinane (Erythrina) alkaloidConcentration: Characterised from Erythrina variegata bark and from Erythrina orientalis, the synonym under which this taxon is often published
Structurally related tetracyclic alkaloids occurring together in the bark as a mixture rather than singly, so the drug delivers a combined nicotinic-antagonist load rather than a single agent. Dimeric and trimeric Erythrina alkaloids have also been isolated from this species, indicating the alkaloid chemistry of the bark is more complex than a simple monomer profile.
Erycristagallin
Prenylated pterocarpan (isoflavonoid)Concentration: Isolated from the stem bark; the most active of seven isoflavonoids screened from this species
A doubly prenylated dehydropterocarpan with bactericidal activity against mutans streptococci and other cariogenic oral bacteria at a minimum inhibitory concentration of 1.56-6.25 microgram per millilitre, acting by blocking thymidine and glucose incorporation into Streptococcus mutans. In vitro data only.
Prenylated isoflavonoids of the stem bark (erystagallin A, orientanol B and congeners)
Prenylated isoflavonoid and pterocarpanConcentration: The dominant non-alkaloid class of the stem bark; several were described as new compounds from this species
The isoflavonoid fraction rather than the alkaloid fraction is what the bone and antibacterial work on this bark is attributed to. Prenylated isoflavonoids are structurally phytoestrogenic, and an ethanolic bark extract suppressed bone turnover and preserved trabecular architecture in ovariectomised rats, consistent with an oestrogen-like action that has not been characterised at receptor level for this species.
⚠ Drug Interactions
Neuromuscular blocking agents used in anaesthesia (rocuronium, vecuronium, atracurium, suxamethonium)
The Erythrina alkaloids are the classical curare-like plant alkaloids: beta-erythroidine, isolated from Erythrina americana in 1937, was developed as a curare substitute and given clinically as a muscle relaxant, and Unna and Greslin's pharmacological series showed that free, liberated and combined alkaloids of Erythrina seeds produce that paralysant action. Two qualifications matter for this record. First, beta-erythroidine is a non-aromatic lactonic erythrinane from a different species; the alkaloids actually characterised from Erythrina variegata bark are aromatic erythrinanes such as erysotrine, erysodine and erythraline, whose defined activity is competitive antagonism at neuronal alpha4beta2 nicotinic receptors rather than potent blockade of the muscle-type receptor. Second, no case of prolonged neuromuscular blockade attributable to this bark has been published. The concern is a real pharmacological family resemblance, not a documented event.
Clinical note: Stop this herb well before elective surgery and record it on the pre-anaesthetic drug history, as you would any herb with nicotinic-receptor activity. Do not assume the bark is inert simply because the curare data come from another Erythrina species, and do not assume it is a potent relaxant either.
Nicotinic receptor drugs for smoking cessation (varenicline, cytisine, nicotine replacement)
Erysodine is a competitive antagonist at neuronal nicotinic acetylcholine receptors with selectivity for the alpha4beta2 subtype - precisely the receptor at which varenicline, cytisine and nicotine replacement act as partial or full agonists. In alcohol-preferring rats erysodine reduced ethanol intake through that receptor, confirming central occupancy in vivo. Concurrent use would be expected to blunt the effect of the cessation agent. The data are preclinical and use the isolated alkaloid, not the bark decoction.
Clinical note: Where a patient is on varenicline or cytisine, expect possible loss of effect rather than toxicity, and prefer a different wind-damp herb for the duration of the cessation attempt.
Monoamine oxidase inhibitors and serotonergic antidepressants
A bark extract of Erythrina variegata produced antidepressant-like effects in mice with measurable regulation of monoamine oxidase activity. If that translates to humans it implies additive monoamine accumulation when combined with an MAO inhibitor, and an unpredictable interaction with SSRIs and SNRIs. This is a single mouse study on the bark, so the evidence level is low, but the affected pathway is one with a serious failure mode.
Clinical note: Avoid combining with phenelzine, tranylcypromine, moclobemide or selegiline. With SSRIs and SNRIs, monitor for serotonergic symptoms rather than assuming no interaction.
Sedatives and CNS depressants (benzodiazepines, Z-drugs, alcohol)
Erythrina variegata is a component of traditional Vietnamese sedative and anxiolytic preparations for insomnia, and a four-herb capsule containing it produced sedative and anxiolytic effects in mice, including potentiation in a diazepam sleep model. The sedative contribution of this species specifically cannot be separated out from the multi-herb formulation, and it was the minor component by weight, so the evidence for the plant alone is weak.
Clinical note: Warn patients about additive drowsiness if they are already on a hypnotic or drinking alcohol, particularly with preparations sold for sleep rather than for joint pain.
Oestrogen replacement therapy, raloxifene and tamoxifen
The stem bark is rich in prenylated isoflavonoids, a structural class with phytoestrogenic potential, and an oral bark extract at 300 and 600 mg/kg for 14 weeks prevented ovariectomy-induced bone loss in rats, suppressing bone turnover markers and preserving trabecular thickness and area. Whether that reflects oestrogen-receptor agonism has not been demonstrated for this species, so the interaction is inferred from the constituent class and the animal endpoint, not measured.
Clinical note: Treat as an unknown in oestrogen-sensitive disease - breast or endometrial cancer, or a patient on tamoxifen - and prefer an alternative rather than trying to dose around it.
Kalopanax septemlobus bark (Ci Qiu Shu Pi) - regional substitution for Hai Tong Pi
In several Chinese provinces the bark of Kalopanax septemlobus, an Araliaceae species carrying triterpenoid saponins, is supplied under the name Hai Tong Pi in place of Erythrina variegata bark, and it is recognised in some municipal materia medica standards as a separate reference material rather than as the same drug. The two share the traditional wind-damp indication but have no chemistry in common: the Erythrina bark carries erythrinane alkaloids and prenylated isoflavonoids, the Kalopanax bark carries saponins. Any monograph statement about alkaloid pharmacology, and any interaction inferred from it, is void if the material dispensed is the Araliaceae bark.
Clinical note: Confirm which botanical the supplier is shipping as Hai Tong Pi, especially for material sourced from Jiangsu, Zhejiang, Anhui or Sichuan. The clinical effect and the interaction profile are not transferable between the two.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 5–15 g | Daily | — | — | Standard oral dose per Xi S, Gong Y. Essentials of Chinese Materia Medica and Medical Formulas. Academic Press/Elsevier, 2017, pp. 117–121. Exact wording: Normally, 5–15 g is decocted with water as an oral |
Evidence Tier
Moderate 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
0
Randomized controlled trial
0
Other clinical trial
0
Observational / case report
0
In vitro / animal
5
4 verified · 1 unverified
Show 5 studies
- Anti-osteoporotic effect of Erythrina variegata L. in ovariectomized rats
- Anti-depressant activity of Erythrina variegata bark extract and regulation of monoamine oxidase activities in mice
- Antibacterial property of isoflavonoids isolated from Erythrina variegata against cariogenic oral bacteria
- Erysodine, a competitive antagonist at neuronal nicotinic acetylcholine receptors
- Erysodine, a competitive antagonist at neuronal nicotinic acetylcholine receptors, decreases ethanol consumption in alcohol-preferring UChB rats
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
Anti-osteoporotic effect of Erythrina variegata L. in ovariectomized rats
Ovariectomised rats given an Erythrina variegata extract orally at 300 or 600 mg/kg for 14 weeks were protected against the oestrogen-deficiency rise in serum osteocalcin and alkaline phosphatase and urinary deoxypyridinoline. Bone histomorphometry showed preserved trabecular thickness and area and reduced trabecular separation dose-dependently, with improved femoral energy absorption and stiffness. An animal study of a whole extract; no human data exist for this indication.
Anti-depressant activity of Erythrina variegata bark extract and regulation of monoamine oxidase activities in mice
A bark extract of Erythrina variegata showed antidepressant-like activity in mouse behavioural models with accompanying changes in monoamine oxidase activity. It is the one study addressing the bark - the plant part that constitutes the drug Hai Tong Pi - rather than the leaf or seed, and it is preclinical. It is included here because monoamine oxidase modulation, if real in humans, has serious interaction consequences.
Antibacterial property of isoflavonoids isolated from Erythrina variegata against cariogenic oral bacteria
Seven isoflavonoids isolated from Erythrina variegata were tested against cariogenic oral bacteria. Erycristagallin was the most active, bactericidal against mutans streptococci, other oral streptococci, Actinomyces and Lactobacillus at a minimum inhibitory concentration of 1.56-6.25 microgram per millilitre, and it inhibited thymidine and glucose incorporation into Streptococcus mutans. Erystagallin A and orientanol B followed at 3.13-12.5 microgram per millilitre. Purely in vitro; no clinical caries endpoint has been tested.
Erysodine, a competitive antagonist at neuronal nicotinic acetylcholine receptors
Characterisation of erysodine, an Erythrina alkaloid, as a high-affinity competitive antagonist at neuronal nicotinic acetylcholine receptors. This is the receptor-level basis for the nicotinic interactions listed for this herb; the work is on the purified alkaloid, not on Erythrina variegata bark, and the alkaloid occurs in several Erythrina species.
Erysodine, a competitive antagonist at neuronal nicotinic acetylcholine receptors, decreases ethanol consumption in alcohol-preferring UChB rats
Erysodine reduced voluntary ethanol intake in alcohol-preferring UChB rats, confirming that this Erythrina alkaloid reaches and occupies central neuronal nicotinic receptors in vivo. Relevant here as evidence that the alkaloid class is centrally active rather than confined to the periphery; it is a study of the isolated alkaloid, not of Erythrina variegata bark.
⚠ Safety & Contraindications
Contraindications
Its use is cautious in patients with blood deficiency. It is not suitable for patients with low back pain without a pattern of wind-damp.
Source: Xi S, Gong Y. Essentials of Chinese Materia Medica and Medical Formulas. Academic Press/Elsevier, 2017, pp. 117–121.
Historical Texts
Kaibao Ben Cao (Materia Medica of the Kaibao Era)
Northern Song dynasty, 973-974Ben Cao Gang Mu (Compendium of Materia Medica), Li Shizhen
Ming dynasty, 1596Ayurvedic use of Paribhadra (Erythrina variegata)
Classical and later Ayurvedic materia medicaReferences
- Chawla A.; Krishnan T.; Jackson A.; Scalabrin D.. Alkaloidal Constituents of Erythrina variegata Bark . Planta Medica (1988) [DOI]
- Ghosal S.; Ghosh D. K.; Dutta S. K.. Occurrence of erysotrine and other alkaloids in erythrina variegata . Phytochemistry (1970) [DOI]
- Ito K.; Furukawa H.; Haruna M.; Lu S.-T.. Studies on the Erythrina Alkaloids. IV. Alkaloids of Erythrina orientalis (L.) MURR. . Yakugaku Zasshi (1973) [DOI]
- Li X.; Wang N.; Wong M. S.; Chen A. S. C.; Yao X.. Four New Isoflavonoids from the Stem Bark of Erythrina variegata . Chemical and Pharmaceutical Bulletin (2006) [DOI]
- Zhang B.-J.; Wu B.; Bao M.-F.; Ni L.; Cai X.-H.. New dimeric and trimeric Erythrina alkaloids from Erythrina variegata . RSC Advances (2016) [DOI]
- Folkers K.; Major R. T.. ISOLATION OF ERYTHROIDINE, AN ALKALOID OF CURARE ACTION, FROM ERYTHRINA AMERICANA MILL. . Journal of the American Chemical Society (1937) [DOI]
- Unna K.; Greslin J. G.. PHARMACOLOGIC ACTION OF ERYTHRINA ALKALOIDS II. FREE, LIBERATED AND COMBINED ALKALOIDS . The Journal of Pharmacology and Experimental Therapeutics (1944) [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.
📝 Notes
Public notes from the community and your own private notes on Hai Tong Pi.
No notes yet.