Scientific Name(s): Abrus precatorius L.
Common Name(s): Bead vine, Black-eyed Susan, Buddhist rosary bead, Crab's eye, Jequirity seed, John Crow beads, Love bean, Lucky bean, Prayer beads, Precatory bean, Rosary pea, Weather plant
A. precatorius is native to southeast Asia and is now found in other tropical and subtropical regions. It is commonly found in Florida and Hawaii where it grows as a slender vine generally supported by other plants or a fence. The plant has clusters of pink flowers, and its compound leaves are sensitive to light, drooping at night and on cloudy days. The fruit splits open as it dries to reveal 3 to 5 hard-coated, brilliant scarlet (or rarely white) seeds with a small black spot at the point of attachment. This spot helps identify the seeds, which are sometimes confused with Rhynchosia, in which the black and red colors are reversed. Seeds of A. precatorius may also be confused with those of Ormosia, also a toxic member of the Fabaceae.1, 2, 3, 4 A synonym is Abrus abrus L.
The precatory bean has found widespread use as an art object and ornament. The colorful, hard beans have been used as pendants, rosaries, rattles, necklaces, and in toys such as noise shakers.5
All parts of the plant have been used in traditional medicine. Dilute infusions have been used in South American and African folk medicine for the treatment of ophthalmic inflammations such as conjunctivitis. Precatory beans have been used medicinally to hasten labor, stimulate abortion, and also have found some use as an oral contraceptive in traditional medicine. The seeds also have been used to treat fever in Chinese medicine. The leaves and roots of the plant have been used in Ayurvedic medicine for treatment of asthma, bronchitis, and other respiratory conditions.1, 4, 6
Because of the great potential for toxicity, the use of this plant is not recommended.
The protein abrin has been isolated from the seed and is responsible for its toxic effects. It is one of the most deadliest poisons in the world, almost twice as potent as the structurally similar ricin (Ricinus communis).9, 10 It has been described as a single glycoprotein of molecular weight 60,000 to 65,000.11 Two proteins of differing amino acid composition have been purified from precatory beans, designated abrin A and C. Abrin C exhibits more potent hemagglutination activity than abrin A.12 Both abrin A and C may be subdivided into smaller units of molecular weight of about 30,000. Abrin is a type 2 ribosome inactivating protein. The toxin is composed of 2 chains (A and B) with distinct functions. The B chain (the haptomere) binds to galactose units of cell surface carbohydrates.13
Another lectin, abrus agglutinin, which is nontoxic to animal cells and exhibits potent agglutinating activity toward erythrocytes, has been described.14 Abrus seeds also contain a potent proteinase inhibitor.15
Uses and Pharmacology
Limited studies have been conducted in animals. Abrin has been used as a molecular probe to investigate cellular function. It has also been evaluated in the treatment of experimental cancers. Although effective when given intraperitoneally to mice pretreated with L1210 leukemia, no increase in lifespan was noted when the compound was administered IV.16 In another study in mice, intraperitoneal abrin over 10 days was effective in reducing solid tumor mass.17 Antidiabetic effects of a methanol leaf extract have been described in rodents.18 Ethanolic extracts of the leaves of Abrus possess d-tubocurarine-like neuromuscular blocking activity.19
Research revels no clinical data as toxicity of the plant has precluded clinical studies. Detoxification of the plant has been studied, potentially facilitating clinical study in the future.20
Clinical studies are lacking for any therapeutic application. Precatory bean is a dangerous poison; one seed if thoroughly chewed has been claimed to be fatal to a child, however the tough, impermeable seed coat reduces its toxic potential.
Pregnancy / Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking. Avoid use.
None well documented.
Because of the irritant effects of abrin on the GI mucosa, ingestion of precatory beans causes severe stomach cramping accompanied by nausea, vomiting, severe diarrhea, cold sweat, and fast pulse.5, 15 Necklaces made of the pierced seeds have been reported to induce dermatitis.21
The seeds, roots, and leaves of A. precatorius are all poisonous. The A chain (effectomere) of the constituent abrin is reportedly responsible for the toxic activity. Once inside the cell, the A chain migrates to the 60S unit of the ribosome, acting to inhibit further protein synthesis. Abrin has a strong inhibitory effect on protein synthesis, moderate inhibitory effect on DNA synthesis, and little effect on RNA synthesis.12
The LD50 of abrin given intraperitoneally to mice is 0.04 mcg;12 5 mg of the alkaloid abrin is reported to be toxic to humans.21 In goats, ground seeds administered at a dose of 1 and 2 g/kg/day caused death in 2 to 5 days.23 The estimated fatal human dose is 0.1 to 1 mcg/kg, almost half that of ricin.9 In children as little as half of one seed has been fatal.1, 5
Coma, circulatory collapse, acute renal failure, and hepatotoxicity have been reported.5, 15 Neurologic symptoms have been reported24 as well as fatalities.1, 5, 10, 24 The toxin is released when the hard outer covering is pierced, thus allowing absorption into the intestinal secretions, by chewing or drilling holes in the seeds for beadwork, ornaments, or jewelry. Intact seeds remain impervious to gastric fluid and pose less of a toxicologic potential.25
The onset of toxicity may be delayed up to 3 days; symptoms may persist for longer than 10 days.9
Treatment is supportive and symptomatic. Because of the necrotizing action of abrin, gastric lavage or induced emesis should be used cautiously.5, 24 Measures to maintain circulation include the correction of hypovolemia and electrolyte disturbances. Alkalinization of the urine to control uremia and enhance toxin excretion has been recommended.5, 9, 10, 26
A radioimmunoassay has been developed for abrin.27
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