The pretty red rosary pea hides a toxin deadlier than ricin
Rosary pea seeds, glossy scarlet with a black spot like a ladybird, are strung into bracelets and rosaries. They also contain abrin, lethal at roughly one seventy-fifth the dose of ricin. Chewing a single seed properly can kill, yet a swallowed whole seed may pass straight through thanks to its hard shell.
Abrus precatorius is a slender climbing member of the bean family, native to Asia and Australia, that twines through trees and hedges. It goes by dozens of names, from crab's eye and jequirity to Indian licorice, since its roots were once used in India as a licorice substitute. Humans spread it widely and birds carried the bright seeds further, so it now grows across the tropics and is a declared weed in places such as Hawaii and Florida, where it invades rare pine rocklands. Deep roots and suckering make an established patch very hard to eradicate.
Abrin works in two parts. Its B chain latches onto transport proteins on a cell's surface to get inside; the A chain then disables ribosomes, the cell's protein factories, and one molecule can knock out up to 1,500 of them per second. In mice the lethal dose is only 0.56 micrograms per kilogram, and one estimate puts a toxic human dose at about 0.1 mg for a 68 kg adult. Poisoning brings vomiting, convulsions and liver failure, often with death after several days, though slow absorption from chewed seeds has left time for rescue in some cases.
A persistent story says jewellery makers die from pricking their fingers while drilling the seeds, but the claim looks thin: a search of 265 scientific papers on the plant found none about workplace poisoning. Even so, the Eden Project and other British outlets recalled bracelets made from the beans in December 2011. In Trinidad such bracelets are worn to ward off evil spirits and the evil eye.
The seeds' hard, waterproof coat keeps their weight remarkably steady, so Indian goldsmiths once used them as weights: eight ratti made a masha, and twelve masha a tola of 11.6 grams. The Tang poet Wang Wei probably had these red beans in mind in his poem One-hearted.
Source: Abrus precatorius
