Scientific Name(s): Physostigma venenosum Balf. f.
Common Name(s): Calabar bean, Chop nut, Esere nut, Faba calabarica, Ordeal bean, Physostigma
Medically reviewed by Drugs.com. Last updated on Mar 22, 2022.
Calabar bean was originally consumed in African rituals, with its toxic constituents often resulting in death. Physostigmine, a main constituent of calabar bean, has been investigated for use in anticholinergic toxicity and in dementia. However, because of the bean's toxicity and lack of clinical trials using the crude plant material or extract, use cannot be supported or recommended for any indication.
Calabar bean's constituent physostigmine has been widely studied as the pure alkaloid available as an approved medication. Clinical data relating to the crude plant material or to an extract are lacking; the bean is toxic and should not be used or ingested.
Contraindications have not yet been identified for calabar bean; however, physostigmine should be avoided in individuals with asthma, cardiovascular disease, diabetes, gangrene, and urinary and GI obstructions.
Avoid use. Adverse effects have been documented.
None well documented.
There are few reports regarding adverse reactions; calabar bean is toxic to humans, with cases of acute toxicity reported. Adverse effects of physostigmine include cramps, twitching, weakness, increased urination, sweating, increased heart rate, seizures, and convulsions.
Physostigmine is extremely toxic, affecting heart contractibility and inducing respiratory paralysis, which can result in death. Physostigmine can also be harmful to the liver.
- Fabaceae (pea/bean)
The calabar bean is the dried ripened seed of P. venenosum, a large, herbaceous perennial climbing plant with woody stems found on the banks of streams in Nigeria, West Africa. The base of the stem grows up to 5 cm in diameter and the plant can reach upwards of 15.25 m in height, bearing showy purple flowers and seed pods that grow to about 15 cm in length. Each pod contains 2 to 3 seeds. The thick dark brown seeds are about 2.5 cm wide and have an extremely hard shell. The beans ripen in all seasons but thrive in abundance during the rainy season (June through September).Aihiokhai 2019, Duke 2002, USDA 2020
The plant is native to an area of Nigeria once known as Calabar, and the seeds were historically used as an "ordeal poison" to determine if a person was a witch, possessed by evil spirits, or guilty of a crime. When used for this purpose, the accused was made to ingest several beans. If they regurgitated the beans and survived the "ordeal," their innocence was proclaimed. Western settlers captured by native tribes and made to undergo the "ordeal" learned not to chew the bean, but to swallow it intact, thereby avoiding release of the toxic constituents. The plant has been long recognized as a commercial source of the alkaloid physostigmine, a reversible cholinesterase inhibitor. The deadly potency of the extract was first noted by European missionaries as early as 1840; observations of the "trial by ordeal" ritual included a case in which a suspect developed cholinergic crisis after swallowing a physostigmine-containing calabar bean. In 1864, physostigmine was first isolated from calabar beans.Dawson 2016, Pope 2018 It was also used experimentally to counteract the effects of atropine and for miotic effects in the eyes.Andrade 2019, Calabrese 2008, Dawson 2016, Karczmar 1998, Nickalls 1988, Proudfoot 2006, Realini 2011
The seeds of P. venenosum contain the major alkaloid physostigmine (eserine), as well as the related alkaloids eseramine, physovenine, calabatine, geneserine, and others. These alkaloids are derived from a tryptophan precursor. Because physostigmine oxidizes to a reddish compound known as rubreserine when exposed to air, it should be protected from air and light.Zhao 2004
Uses and Pharmacology
Physostigmine alone is an acetylcholinesterase inhibitor that prolongs the neuronal activity of acetylcholine. Given its ability to cross the blood-brain barrier, it is used to reverse the CNS toxicity (eg, anxiety, delirium, disorientation, hyperactivity, hallucinations, and seizures) of anticholinergic drugs, including tricyclic antidepressants and scopolamine.Andrade 2019, Dawson 2016, Malamed 2018, Pakala 2019
Animal and in vitro data
Physostigmine-loaded liposomes have been evaluated in vitro and in pharmacokinetic studies in rats to determine the feasibility of prolonging the physostigmine half-life in order to extend protection against the effects of nerve gas exposure that lead to nerve-agent poisoning. The liposomes aided in maintaining constant plasma concentrations of physostigmine.Park 2018
Physostigmine from the calabar bean has been investigated for its ability to increase cognition, particularly in patients with Alzheimer disease, but with minimal success.Howes 2011, Howes 2012
Calabar bean's constituent physostigmine has been widely studied as the pure alkaloid available as an approved medication. Clinical data relating to the crude plant material or to an extract are lacking; the bean is toxic and should not be used or ingested.Duke 2002
Pregnancy / Lactation
Avoid use. Adverse effects have been documented.Ernst 2002
None well documented.
There are few reports regarding adverse reactions; calabar bean is toxic to humans, with cases of acute toxicity reported. A study of Wistar rats given P. venenosum extract ranging from 10 to 30 mg/kg/day for 2 weeks displayed signs of hepatic injury.Aihiokhai 2019 CNS effects of physostigmine, which include ataxia and convulsions, can eventually lead to coma.Andrade 2019 Other observed severe adverse reactions include tachycardia and tachyarrhythmia.Pinder 2019 More severe adverse reactions are typically due to overdose. Less severe adverse reactions include GI disturbances, dyspnea, miosis, sweating, hypertension, salivation, headache, and lacrimation.Andrade 2019, Dawson 2016, Effenberger-Neidnicht 2018, Malamed 2018, Pinheiro 2018
Physostigmine is extremely toxic, with an oral median lethal dose of 4.5 mg/kg in mice. Physostigmine affects heart contractility and induces respiratory paralysis, which can result in death; 2 to 3 beans are sufficient to be lethal.Duke 2002 Based on hepatic injury demonstrated in rats, a P. venenosum extract dose of 20 mg/kg/day should not be exceeded over an extended period of time.Aihiokhai 2019 In the event of physostigmine toxicity, atropine or oximes (eg, pralidoxime) are utilized as antidotes.Andrade 2019, Pakala 2019 Excessive administration of physostigmine can lead to cholinergic toxicity and should be used with caution. Signs of cholinergic toxicity include hypersecretion, salivation, lacrimation, bronchospasm, bradycardia, nausea, vomiting, diarrhea, neuromuscular weakness, coma, and seizures.Dawson 2016, Pakala 2019
This information relates to an herbal, vitamin, mineral or other dietary supplement. This product has not been reviewed by the FDA to determine whether it is safe or effective and is not subject to the quality standards and safety information collection standards that are applicable to most prescription drugs. This information should not be used to decide whether or not to take this product. This information does not endorse this product as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this product. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this product. This information is not specific medical advice and does not replace information you receive from your health care provider. You should talk with your health care provider for complete information about the risks and benefits of using this product.
This product may adversely interact with certain health and medical conditions, other prescription and over-the-counter drugs, foods, or other dietary supplements. This product may be unsafe when used before surgery or other medical procedures. It is important to fully inform your doctor about the herbal, vitamins, mineral or any other supplements you are taking before any kind of surgery or medical procedure. With the exception of certain products that are generally recognized as safe in normal quantities, including use of folic acid and prenatal vitamins during pregnancy, this product has not been sufficiently studied to determine whether it is safe to use during pregnancy or nursing or by persons younger than 2 years of age.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Copyright © 2023 Wolters Kluwer Health