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Chapter: Modern Medical Toxicology: Organic Poisons (Toxins): Irritant Plants

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Rosary Pea - Gastric Irritant Plants

Rosary Pea - Gastric Irritant Plants
Other Common Names: Jequirity bean; Indian bead; Buddhist rosary bead; Rosary pea; Seminole bead; Prayer bead; Jungle bead; Crab’s eye; Weather plant; Love bean; Lucky bean; Ojo de pajaro; Indian liquorice. Botanical Name: Abrus precatorius.

Rosary Pea

Other Common Names

Jequirity bean; Indian bead; Buddhist rosary bead; Rosary pea; Seminole bead; Prayer bead; Jungle bead; Crab’s eye; Weather plant; Love bean; Lucky bean; Ojo de pajaro; Indian liquorice.

Botanical Name

Abrus precatorius.

Physical Appearance

·      This green vine belongs to family Leguminosae, and is a tropical, ornamental, twining, woody vine which grows to a height of 10 to 20 feet when supported by other plants.

·      It has slender, tough branches with 5 to 10 cm long compound leaves bearing 10–20 pairs of leaflets (Fig 10.19). Leaves are alternate, opposite, pinnately divided (feather-like) with small oblong leaflets. Leaflets appear in 8 to 15 pairs, and are about ½ inch long.

·      Stems are green when young, but develop grey bark as the plant matures.

·      Flowers are pink, purple, or white and borne in clusters. They appear in the leaf axils along the stems.

·      The distinctive part of the plant is the seed which is oval, 5 mm in diameter, and has an attractive hard glossy outer shell that is usually scarlet red with a black centre (Fig 10.20).* 

The seeds are present inside fruit pods, each containing 3 to 5 seeds. The pods split open when ripe. The pod is a legume (pea-shaped pod), and is about 3 cm long.



Uses

·     The seeds are often used in rosary beads, necklaces, and folk jewellery.

·      Jewellers in India sometimes use the seeds as a weighing measure for gold or precious stones.

·     Quacks use extracts of various parts of the plant for the treatment of a wide variety of ailments.

Toxic Part

Seeds, root, leaves.

Toxic Principles

Abrin, abric acid, glycyrrhizin, and N-methyl tryptophan. The main active principle is abrin which is a toxalbumen very similar to ricin. It is a lectin composed of two polypeptide chains (A and B) connected by a disulfide bridge. This basic structure of two peptide chains linked by a single disulfide chain is similar to that of botulinum toxin, tetanus toxin, cholera toxin, diphtheria toxin, and insulin.

Mode of Action

Like castor, the seeds of abrus are harmless when ingested whole, since the hard outer shell resists digestion. However, chewing or crushing of the seed before swallowing will enable the toxins to be released. Abrin is a powerful gastrointestinal toxin, and one of its polypeptide chains (B) binds to the intestinal cell membrane, while the other chain (A) enters the cytoplasm. Once in the cell, the A chain acts on the 60S ribosomal sub-unit, preventing binding of elongation factor 2, thus inhibiting protein synthesis and leading to cell demise.

Clinical Features

·      Dermal contact: redness, rash.

·      Ocular exposure: reddening, swelling, blindness.

·      Ingestion:

o     Burning pain in the mouth and throat

o     Severe vomiting

o     Abdominal pain

o     Bloody diarrhoea

o     Cardiac arrhythmias

o     Convulsions

o     CNS depression

o     Cerebral oedema

o     Elevations of liver enzymes.

Usual Fatal Dose

·              About 1 to 3 seeds.

·              A point to note is that there have been several cases of inges-tion of large amounts of seeds, which have resulted in scant clinical effects. This may reflect variations in toxicity, and/or poor GI absorption. If the seeds of these plants are swallowed whole, symptoms are much less likely to occur.

Treatment

·      Gastric decontamination (lavage, charcoal).

·      Whole bowel irrigation is said to be helpful, but some investigators dispute this.

·       Supportive measures, with special emphasis on rehydration. Close attention should be given to haematological parameters.

·     Alkalinisation of the urine probably has a role in preventing crystallisation of haemoglobin, and should be considered in severe poisonings.

·      Treat convulsions in the usual manner with diazepam.

·      Renal failure can be managed by haemodialysis.

·      Ocular exposure necessitates copious irrigation with running water for at least 15 minutes.

Autopsy Features

·              Evidence of GI haemorrhage, oedematous bowel, cerebral oedema, and congested liver and kidneys.

Forensic Issues

■■   Accidental poisoning is not uncommon among children playing in the countryside who find the seeds very attractive and may bite or chew on them.

■■   The extract of the seed is used in rural India to kill cattle by injecting needles (“suis”) made out of the dried seed paste.

■■   Homicides have been reported with “suis”.

 

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