Abrin: More Deadly and Less Common than Ricin

By Chris Healey

Abrin was among toxins found during an apartment search of a San Francisco man charged with possessing explosive material. An FBI affidavit states the suspect told investigators he acquired abrin to ease the suffering of cancer patients.

Abrin is a protein-based toxin from the jequirity bean, colloquially known as a rosary bead. The toxin is lethal in minute doses and causes serious symptoms in even smaller amounts. It is almost identical to a better-known toxin—ricin. Abrin is more lethal than ricin. Toxicologists estimate abrin’s lethal dose between .1 and 1 microgram per kilogram. In comparison, ricin is lethal between 5 and 10 micrograms per kilogram.

Both abrin and ricin consist of two proteins, A chain and B chain, linked by a disulfide bond. The proteins work together to enter the cell and disrupt its activity. B chain grants cell entry, while A chain transports to the ribosome and destroys it. Cells die shortly after ribosome destruction.

Abrin’s nonuse despite toxic superiority to ricin is ostensibly due to a matter of availability. As a byproduct of castor oil, an ingredient in soap and mechanical lubricant, ricin is very common. Conversely, rosary beads serve a limited purpose in prayer and are not consumed or destroyed in their role. One set of rosary beads can last for years before replacement is necessary. Their limited and reusable role makes them uncommon.

Availability also contributes to abrin and ricin’s historical precedence. According to a study conducted by the Federation of American Scientists, ricin has been maliciously used 37 times since 1983. Malicious abrin use is almost nonexistent except for several reports in India and Sri Lanka in the early 20th century.

Abrin is released from crushed jequirity beans. Individuals who handle beans whole and unaltered, as in prayer, are not exposed. Even in cases of jequirity bean ingestion, intoxication is dependent on how thoroughly beans are chewed. Symptoms include nausea, vomiting, diarrhea, abdominal pain, and colic. Some less common symptoms include irregular heartbeat, irrationality, hallucinations, and seizures. In fatal cases, cause of death has been traced to gastrointestinal damage.

Abrin is a select agent designated by the Department of Health and Human Services. It is illegal to manufacture or possess any quantity of the toxin. Although jequirity beans contain abrin, they are not illegal. The law is broken when abrin toxin is isolated from a bean.


(Image Credit: Satdeep gill)

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