Xing Ren
StarPrunus armeniaca
Synonyms: Armeniaca armeniaca, Armeniaca vulgaris, Amygdalus armeniaca, Prunus tiliifolia
Traditionally used for
- Cough & breathing
- Bowel health
- Menstrual & women's health
- Pain & joints
Cautions & contraindications
- Pregnancy
- Young children
- Liver conditions
- Toxic — professional use only
☯ TCM Properties
Stops coughing and calms wheezing; Moistens the Intestines and unblocks the bowels
Traditional Chinese Uses
Xing Ren (杏仁), more precisely Ku Xing Ren (苦杏仁), is the kernel of Prunus armeniaca L. and related apricots (Rosaceae), Semen Armeniacae Amarum. It is bitter and slightly warm and slightly toxic, entering the Lung and Large Intestine channels. It stops coughing and calms wheezing, and moistens the Intestines to unblock the bowels.
It is the principal herb for cough and wheezing of nearly any origin, because its bitterness directs Lung Qi downward — the direction Lung Qi should travel and fails to when there is cough. It is combined according to the pattern: with Ma Huang for Wind-Cold wheezing in Ma Huang Tang, with Sang Ye and Ju Hua for Wind-Heat cough in Sang Ju Yin, with Shi Gao for Lung Heat in Ma Xing Shi Gan Tang. Its oily kernel also moistens dry Intestines, and it is used for constipation in the elderly, the postpartum and the depleted.
The toxicity is real and dose-limiting. The bitter kernel contains amygdalin, which releases hydrogen cyanide on hydrolysis; this underlies both the cough-suppressing action and the danger. The drug is blanched and the tip removed before use, and it is decocted rather than eaten raw. The usual dose is 3 to 10 g. Children are markedly more susceptible, and cases of fatal poisoning in children from eating raw bitter apricot kernels are well documented. It is used with caution in infants and in diarrhoea. Tian Xing Ren, the sweet kernel, is much lower in amygdalin, weaker in action and used more as a food.
Western Herbalism Properties
Pharmacological Effects
- Antitussive and antiasthmatic: Oral amygdalin inhibited SO2-induced cough in mice; attributed to enzymatic release of small amounts of hydrocyanic acid acting reflexively on the respiratory centre.
- Laxative: The abundant fatty oil lubricates the intestine.
- Analgesic: S.c. amygdalin was analgesic in mice (ED50 457 mg/kg hot plate, 288 mg/kg writhing), lasting over 4 h; proteins KR-A and KR-B also analgesic/antiinflammatory.
- Antineoplastic and antimutagenic: Controlled animal studies did not confirm antitumour activity of amygdalin, which is largely excreted unchanged; oleic and linoleic acids showed tumour inhibition; hexane extract was antimutagenic in the Ames assay against B(a)P, Trp-P-1 and AF-2.
Source: Zhu YP. Chinese Materia Medica: Chemistry, Pharmacology and Applications. Harwood Academic, 1998, p. 496.
Used In Formulas (40)
Relationships
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Gallery
Botanical Description
Prunus armeniaca is a deciduous tree reaching 5-12 m tall. Bark is reddish-brown and furrowed. Leaves are broadly ovate, 5-10 cm long, with a pointed tip and finely toothed margins. Flowers are white to pale pink, 5-petaled, appearing before the leaves in early spring. The fruit is a fleshy drupe 3-5 cm in diameter, orange-yellow to red when ripe. The hard stone (pit) encloses the almond-like seed (kernel). In TCM, both bitter (northern, Ku Xing Ren) and sweet (southern, Tian Xing Ren) seeds are used.
Rocky hillsides, forest margins, and river valleys; native to Central Asia (China, Uzbekistan, and surrounding regions), widely cultivated in warm temperate regions worldwide for its fruit.
Prunus armeniaca is widely cultivated worldwide and naturalized in many regions. Native populations in Central Asia may face some pressure from habitat change. The cultivated form has no conservation concerns.
Active Constituents
Amygdalin
Cyanogenic diglucoside (mandelonitrile gentiobioside)Concentration: Commonly 2-5% of dry weight in bitter kernels; sweet (Tian Xing Ren) kernels are typically an order of magnitude lower. Content varies with cultivar, altitude and kernel maturity.
The defining constituent of the drug and the source of both its reputed antitussive action and all of its toxicity. Two sequential hydrolyses release benzaldehyde, glucose and hydrogen cyanide; the aglycone mandelonitrile is what actually decomposes to HCN. Amygdalin is chiral at the mandelonitrile carbon and the D- and L- epimers are metabolised differently, which is why processing and co-decoction change the toxic yield.
Prunasin
Cyanogenic monoglucosideConcentration: Minor in the mature kernel; accumulates earlier in kernel development and is the obligate intermediate of amygdalin hydrolysis in vivo
The single-sugar intermediate between amygdalin and free mandelonitrile. Circulating D-prunasin concentration correlates with acute toxicity in animal work, so anything that lowers it lowers the cyanide burden.
Emulsin (amygdalin beta-glucosidase, prunasin hydrolase and mandelonitrile lyase)
Plant beta-glucosidase enzyme complexConcentration: Present in the raw kernel, compartmentalised away from amygdalin until the tissue is crushed, chewed or wetted
The enzyme complex that converts amygdalin to hydrogen cyanide within minutes of the kernel being chewed or ground into cold water. It is heat-labile: brief blanching in boiling water (the Chinese Pharmacopoeia chan process, which also slips off the seed coat) denatures it, and this - not removal of amygdalin - is the mechanism by which processing makes the drug safer to decoct.
Hydrogen cyanide
Inorganic nitrile released on hydrolysis; cytochrome c oxidase inhibitorConcentration: Not present in the intact kernel; released stoichiometrically from amygdalin, so cyanide yield tracks amygdalin content
The actual toxicant. It binds ferric iron in cytochrome c oxidase, blocking mitochondrial respiration and producing histotoxic hypoxia with a rising lactate, a narrow arteriovenous oxygen difference and seizures. EFSA derived an acute reference dose of 20 micrograms cyanide per kg body weight and reported a lethal dose of 0.5-3.5 mg/kg body weight.
Fatty oil (triacylglycerols rich in oleic and linoleic acid)
Fixed oil / triglyceridesConcentration: Roughly 35-50% of the kernel
The bulk of the seed by mass and the plausible basis of the classical moistening-the-intestines and unblocking-the-bowels indication, which is a lubricant laxative effect rather than a stimulant one. It carries none of the cyanogenic risk.
Seed storage protein and free amino acids
ProteinConcentration: Roughly a quarter of the defatted kernel
Nutritionally significant but not pharmacologically characterised; apricot kernel protein hydrolysates have been studied for antioxidant activity in food-science work rather than in a clinical context.
⚠ Drug Interactions
Amygdalin or laetrile products sold as vitamin B17
Laetrile and amygdalin supplements are the same cyanogenic molecule as the herb's principal constituent, so taking them alongside Xing Ren simply stacks the cyanide dose. Oral amygdalin produces blood cyanide levels that the intravenous route does not, and there is a documented fatality series: a JAMA case report of fatal poisoning after accidental amygdalin ingestion, a clinicopathologic study of cyanide neuromyopathy in a laetrile user, and a teenager with severe lactic acidosis after intentional amygdalin ingestion. The Cochrane review found no reliable evidence of any anticancer benefit to set against this risk, and the NCI phase II trial found no cure, improvement or stabilisation while patients developed symptoms of cyanide toxicity.
Clinical note: Ask directly about vitamin B17, laetrile, apricot kernel capsules and raw kernel eating before prescribing Xing Ren, and do not prescribe the herb alongside them. There is no therapeutic reason to add a laetrile product to a formula that already contains the kernel.
Tao Ren (Prunus persica seed), Yu Li Ren (Prunus humilis / P. japonica seed) and other cyanogenic Rosaceae kernels
Tao Ren and Yu Li Ren are amygdalin-bearing kernels from the same genus and hydrolyse to hydrogen cyanide by the same route; Tao Ren already exists in this corpus as a separate record with the same chemistry. Because cyanide detoxification by rhodanese is saturable and depends on a finite thiosulfate sulfur pool, the toxic effect of several cyanogenic kernels in one formula is additive rather than independent. Tao Ren and Xing Ren are also mutually substituted in trade, so a formula can carry more cyanogenic kernel than the prescription states.
Clinical note: Treat the total cyanogenic kernel content of a formula as one dose, not several. Where Xing Ren and Tao Ren appear together, keep each at the low end of its pharmacopoeial range, insist on processed (blanched) material, and do not extend the course in children, in pregnancy or in hepatic impairment.
Ku Xing Ren from Prunus sibirica, P. mandshurica or P. armeniaca var. ansu (bitter kernel substitution)
The official bitter apricot kernel drug is drawn from several Prunus taxa, of which P. armeniaca is only one, and sweet apricot kernel (Tian Xing Ren) from the same species is also traded under the Xing Ren name. Amygdalin content differs greatly between bitter and sweet kernels and varies further with cultivar, altitude and maturity, so which taxon and which grade reached the dispensary determines both the antitussive dose and the cyanide dose. Substitution in either direction is unlabelled: sweet-for-bitter under-doses the intended active, bitter-for-sweet delivers a cyanogenic load the prescriber did not intend.
Clinical note: Specify bitter (Ku Xing Ren) or sweet (Tian Xing Ren) explicitly on the prescription and buy from a supplier who assays amygdalin. Do not assume that a batch labelled only Xing Ren is the bitter pharmacopoeial drug, and do not carry a dose forward from one supplier to another.
Ma Huang (Ephedra sinica)
The Mahuang-Xingren pair that underlies Ma Huang Tang and Ma Xing Shi Gan Tang is not merely additive. In mice, Ma Huang antagonised the acute toxicity of Xing Ren and permitted dose escalation, and the effect tracked the D-amygdalin proportion: co-decoction shifts the epimer balance and lowers circulating D-prunasin. A follow-up pharmacokinetic and metabolite study found the traditional co-boiled decoction generated more detoxified (deaminated, non-cyanogenic) metabolites than dispensing granules of the same two herbs combined dry, and identified gut microbial enzymes as faster than liver microsomes at metabolising amygdalin.
Clinical note: This is an argument for co-decocting the pair rather than reconstituting it from separate granules. It is not a licence to raise the Xing Ren dose: the protective effect was shown in rodents, and Ma Huang carries its own sympathomimetic cardiovascular and pressor risks and is legally restricted in several jurisdictions.
Broad-spectrum oral antibiotics
Amygdalin taken by mouth is largely hydrolysed by beta-glucosidases of the gut flora rather than by human enzymes; germ-free and antibiotic-treated rats are markedly protected from oral amygdalin toxicity, which is the classical demonstration that the microflora is the activating compartment. Human metabolite work on the Ephedra pair similarly found gut microbial enzymes hydrolysing amygdalin faster than liver microsomes. The practical corollary cuts both ways: a course of antibiotics can blunt the herb's cyanide yield, and the yield returns, unpredictably, as the flora recolonises.
Clinical note: Do not read a well-tolerated Xing Ren dose taken during an antibiotic course as evidence the dose is safe afterwards. Re-establish tolerance at the low end of the range once antibiotics finish, particularly in children.
High-dose ascorbic acid (vitamin C)
In guinea pigs, high-dose ascorbic acid decreased detoxification of cyanide derived from amygdalin, attributed to depletion of the cysteine sulfur pool that rhodanese requires to convert cyanide to thiocyanate. The evidence is animal and the dose was supraphysiological, but high-dose vitamin C is exactly the co-intervention most likely to be taken by the population that seeks out apricot kernel products.
Clinical note: Ask about gram-dose vitamin C supplementation, which frequently travels with laetrile use, and separate it from the herb; treat the combination as a reason to keep Xing Ren at the low end of the range rather than as a neutral pairing.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 5–10 g | daily | — | adult | 中国药典 2020年版 一部 【苦杏仁】【用法与用量】5～10g，生品入煎剂后下。 【注意】内服不宜过量，以免中毒。 — Chinese Pharmacopoeia 2020, Vol. I. Bitter apricot kernel is slightly toxic (amygdalin); do not exceed usual dose and add near end of decoction. Use with caution in infants. |
Dui Yao — Herb Pairs
The classical two-herb combinations this herb appears in, each with an action neither herb has alone.
Descend lung qi and transform phlegm to calm wheezing.
Wheezing in an exterior pattern or chronic wheezing with phlegm. Xing Ren is mildly toxic in overdose.
Core pair of a classical formula — Gui Zhi Jia Hou Po Xing Zi Tang, Shang Han Lun (Zhang Zhongjing)
Oily moistening of the intestines combined with descending of Lung qi, which helps move the bowels because the Lung and Large Intestine are paired.
Dry constipation with intestinal dryness (spleen-binding pattern).
Core pair of a classical formula — Ma Zi Ren Wan, Shang Han Lun (Zhang Zhongjing)
One disperses and opens the lungs, the other descends lung qi; the combined dispersing and descending restores lung function and strengthens the calming of wheezing and cough.
Also core to Ma Huang Tang (Shang Han Lun).
Core pair of a classical formula — San Ao Tang, Tai Ping Hui Min He Ji Ju Fang
Lightly disperses wind-heat and dryness from the lungs while descending lung qi and moistening, stopping dry cough.
Warm-dryness attacking the lungs.
Core pair of a classical formula — Sang Xing Tang, Wen Bing Tiao Bian (Wu Jutong)
Lightly releases the exterior while descending and moistening lung qi, for cool-dryness or wind-cold cough.
Cool-dryness: mild headache, aversion to cold, cough with thin sputum, dry nose and throat.
Core pair of a classical formula — Xing Su San, Wen Bing Tiao Bian (Wu Jutong)
Evidence Tier
Strong evidence · 7 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
0
Other clinical trial
1
1 verified · 0 unverified
Observational / case report
1
0 verified · 1 unverified
Show the study
In vitro / animal
4
0 verified · 4 unverified
Show 4 studies
- Stereoselective metabolism of amygdalin-based study of detoxification of Semen Armeniacae Amarum in the Herba Ephedrae-Semen Armeniacae Amarum herb pair
- Interactions Between Ephedra sinica and Prunus armeniaca: From Stereoselectivity to Deamination as a Metabolic Detoxification Mechanism of Amygdalin
- Improvement of the extraction efficiency of d-amygdalin from Armeniacae Semen powder through inactivating emulsin and suppressing the epimerization of d-amygdalin
- Accumulation Pattern of Amygdalin and Prunasin and Its Correlation with Fruit and Kernel Agronomic Characteristics during Apricot (Prunus armeniaca L.) Kernel Development
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
Laetrile treatment for cancer
Cochrane review of laetrile and amygdalin as a cancer treatment. The reviewers found no randomised or controlled clinical trial that met inclusion criteria and concluded that the claim of anticancer benefit is not supported by sound clinical data, while the risk of serious adverse effects from cyanide poisoning is substantial. The benefit-risk balance is unambiguously unfavourable.
A Clinical Trial of Amygdalin (Laetrile) in the Treatment of Human Cancer
The National Cancer Institute single-arm phase II trial in 178 patients with advanced cancer, given amygdalin on a schedule and with the metabolic therapy its proponents specified. No patient was cured or stabilised by the treatment; disease progressed in essentially all of them within months, and several developed symptoms and blood cyanide levels indicating cyanide toxicity. This remains the definitive human efficacy evidence for the kernel's cyanogenic constituent.
Pharmacology of amygdalin (laetrile) in cancer patients
Clinical pharmacology companion to the NCI trial. Oral amygdalin produced measurable blood cyanide and thiocyanate concentrations that the intravenous route did not, establishing that the oral route is the toxic one because hydrolysis occurs in the gut. This is the pharmacokinetic basis for treating chewed or powdered raw kernel as far more dangerous than the same amygdalin given parenterally.
Stereoselective metabolism of amygdalin-based study of detoxification of Semen Armeniacae Amarum in the Herba Ephedrae-Semen Armeniacae Amarum herb pair
Acute toxicity in mice given aqueous extracts of Ma Huang, Xing Ren and the pair. Ma Huang antagonised the acute toxicity of Xing Ren and allowed the Xing Ren dose to be escalated; the degree of antagonism correlated with the proportion of D-amygdalin, and the pairing reduced circulating D-prunasin. The paper is the mechanistic case that the classical pairing is a detoxification strategy rather than a simple additive combination.
Interactions Between Ephedra sinica and Prunus armeniaca: From Stereoselectivity to Deamination as a Metabolic Detoxification Mechanism of Amygdalin
Rat pharmacokinetics plus liver-microsome and gut-microbial incubations comparing the traditional co-boiled decoction with dispensing granules. Fifteen amygdalin metabolites were characterised and split into cyanogenic and non-cyanogenic (deamination) pathways; the co-boiled decoction produced more of the detoxified metabolites than the granules, and gut microbial enzymes hydrolysed amygdalin faster than liver microsomes. A corrigendum was published in 2022; the paper is corrected, not retracted.
Improvement of the extraction efficiency of d-amygdalin from Armeniacae Semen powder through inactivating emulsin and suppressing the epimerization of d-amygdalin
Analytical study showing that unless emulsin is deliberately inactivated, apricot kernel powder loses D-amygdalin rapidly on wetting, and that D-amygdalin also epimerises to the L- form under the conditions used to extract it. The practical reading for the dispensary is that the enzyme, not the glycoside, is the controllable variable, and that heat treatment of the kernel is what determines how much cyanide a preparation can generate.
Accumulation Pattern of Amygdalin and Prunasin and Its Correlation with Fruit and Kernel Agronomic Characteristics during Apricot (Prunus armeniaca L.) Kernel Development
Analytical survey of amygdalin and prunasin through kernel development across apricot genotypes. Prunasin dominates early and is largely converted to amygdalin as the kernel matures, and final amygdalin content varies severalfold between genotypes. It is the quantitative basis for treating batch-to-batch amygdalin variation, rather than a single textbook figure, as the operative dosing uncertainty.
⚠ Safety & Contraindications
- Pregnancy
- Young children
- Liver conditions
- Toxic — professional use only
Contraindications
Use with caution in children and in pregnancy. Not for use in diarrhoea from deficiency.
Side Effects
- Oral overdose can cause cyanide poisoning, especially in children; symptoms (dizziness, nausea, vomiting) appear 0.5–5 h after ingestion; severe cases may progress to coma and death from tissue anoxia.
Source: Zhu YP. Chinese Materia Medica: Chemistry, Pharmacology and Applications. Harwood Academic, 1998, p. 496.
Safety Warnings
- Toxicity is dose-related; the Pharmacopoeia dose should not be exceeded, particularly in children.
- Cooking or processing reduces the cyanogenic content.
- Bitter apricot kernel (Ku Xing Ren) is the graded drug; the sweet kernel is far lower in amygdalin.
⚠ Rule-Based Cautions
These entries come from the deterministic rule tables that gate Verscienta's formula tools — classical pair prohibitions, pregnancy and lactation contraindications, and dose ceilings.
Dose Ceiling
≤10g — amygdalin/cyanogenic; typical 5–10g
⚠ Toxicity Information
Headache, dizziness, nausea and vomiting, then in serious poisoning the signs of cyanide toxicity — dyspnoea, cyanosis, convulsion and coma. Children are markedly more susceptible.
Historical Texts
Shen Nong Ben Cao Jing (Divine Husbandman's Classic of the Materia Medica)
Han dynasty, compiled by the 2nd century CEShang Han Lun (Treatise on Cold Damage), Zhang Zhongjing
Late Han dynasty, c. 200-220 CELei Gong Pao Zhi Lun (Master Lei's Treatise on Preparing Drugs)
Attributed to the Liu Song period, c. 5th century CEBen Cao Gang Mu (Compendium of Materia Medica), Li Shizhen
Ming dynasty, 1596References
- EFSA Panel on Contaminants in the Food Chain (CONTAM). Acute health risks related to the presence of cyanogenic glycosides in raw apricot kernels and products derived from raw apricot kernels . EFSA Journal (2016) [DOI]
- Lasch Eli E., Shawa Raghda El. Multiple Cases of Cyanide Poisoning by Apricot Kernels in Children from Gaza . Pediatrics (1981) [DOI]
- Sayre James W., Kaymakcalan Sukru. Cyanide Poisoning from Apricot Seeds among Children in Central Turkey . New England Journal of Medicine (1964) [DOI]
- Tress Jonathan H.. Fatal Cyanide Poisoning: Accidental Ingestion of Amygdalin . JAMA: The Journal of the American Medical Association (1977) [DOI]
- Green Jack. Severe lactic acidosis from acute cyanide poisoning after intentional amygdalin ingestion in a teenager . Emergency Care Journal (2020) [DOI]
- Kalyanaraman Uma P., Kalyanaraman Krishna, Cullinan Stephen A., McLean John M.. Neuromyopathy of cyanide intoxication due to "laetrile" (amygdalin). A clinicopathologic study . Cancer (1983) [DOI]
- Carter John H., McLafferty Martha A., Goldman Peter. Role of the gastrointestinal microflora in amygdalin (laetrile)-induced cyanide toxicity . Biochemical Pharmacology (1980) [DOI]
- Basu Tapan K.. High-dose ascorbic acid decreases detoxification of cyanide derived from amygdalin (laetrile): studies in guinea pigs . Canadian Journal of Physiology and Pharmacology (1983) [DOI]
- Milazzo Stefania, Lejeune Stephane, Ernst Edzard. Laetrile for cancer: a systematic review of the clinical evidence . Supportive Care in Cancer (2006) [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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