Common Name: Calabar Bean

General Information

Calabar bean is an evergreen, scrambling or climbing shrub producing woody stems up to 15 metres long that twine around other plants for support. The stems are around 1cm in diameter[].
A highly poisonous plant, it was formerly used as an ordeal poison to determine guilt in accused people. It also has a number of medicinal applications, but is more commonly grown for the alkaloids contained in the seeds which are extracted and used in modern medicine[, ]. The seeds are normally gathered from the wild, though some cultivation is practiced, particularly in India[].

Known Hazards

The seed is highly poisonous[]. It used to be used in Nigeria in an 'ordeal by poison' where a suspected criminal had to drink a solution of the beans - if it killed them they were guilty but if they survived they were innocent[]. This probably worked to a certain extent in as much as innocent people were more likely to consume the drink in one gulp and then vomit before too much of the toxin had been absorbed, whilst guilty people were more likely to sip it slowly and cautiously, thereby ensuring that more of the toxins were absorbed[].

Botanical References

Range

West tropical Africa - Sierra Leone to Gabon and DR Congo.

Habitat

Closed rain-forests, primary and secondary, dry and wet; riparian seasonally flooded forest; marshes[].

Properties

Medicinal Rating
Habit	Evergreen Climber
Height	10.00 m
Cultivation Status	Cultivated, Wild

Cultivation Details

Requires a minimum temperature of 15 - 18°c[].
Prefers a sunny position in a rich, well-drained soil[].

Edible Uses

None known

Medicinal

Although highly poisonous, the seed has a number of medicinal applications[]. It is a narcotic herb that depresses the central nervous system, mimics the para-sympathetic nervous system, contracts the pupil of the eye, raises blood pressure and stimulates peristalsis[].

The seed contains a number of alkaloids including physostigmine, which has been shown to influence the para-sympathetic nervous system[].
Physostigmine is isolated from the seed and used in eye drops to reduce pressure on the eyeball in treating conditions such as glaucoma[]. It is also prescribed for internal use in the treatment of neuromuscular diseases, especially myasthenia gravis, and for treating post-operative constipation[].

The whole seed is used in herbalism, but should only be prescribed by qualified practitioners[]. It has been used in the treatment of conditions such as tetanus, epilepsy and rheumatism[]. Used in excess, it causes muscular weakness, respiratory failure and cardiac arrest[].

Other Uses

None known

Propagation

Seed - best sown when ripe[].

Add a Comment:

If you have any useful information about this plant, please leave a comment. Comments have to be approved before they are shown here.

Name:

Email(Private):

Message:

Captcha: How many suns are in our solar system