In September 1978, Bulgarian dissident Georgi Markov was assassinated in London, injected by a modified umbrella with a lethal dose of what was mostlikely #RICIN.
Ricin is a protein of the castor bean plant (Ricinus communis, Euphorbiaceae);despite the name, the plant is only distantly related to the bean family (Fabaceae).Human use of castor beans appears to precede recorded history, and Egyptianrecords of their use go back to 1500 BC (see Polito et al, 2019).
Castor beans today are used mainly to produce oil that is mostly #ricinoleicacid, a fatty acid not found widely elsewhere. Absent from the oil is the hydrophilic protein Ricin. However whole beans and oil-pressing residues have significantamounts of ricin, limiting the amounts that can be ingested by humans or addedanimal feeds.
Purified ricin is one of the most potent toxins known but not as toxinas botulinum. Unravelling its mode of action took many years of research(reviewed in Polito et al, 2019), and the main mechanism seems to be to bind to and inhibition of the ribosomes, which are an essential part of the protein synthesis machinery needed to keep cells alive. In analogy, many commonantibiotics (e.g. streptomycin) target the ribosomes of bacteria.
Ricin is not an instant killer like cyanide or carbon monoxide that both cut off the biological energy supply – no ATP, cells die immediately. Death from ricin intoxication, however, can take many hours, a consequence of toxicity by inhibiting protein synthesis. Cells have a lot of protein, some very long-lived (years), but some turning over rapidly (days or hours) particularly hormones and other signalling molecules. Cell death occurs when certain essential proteins become depleted to levels when the cell can no longer function.
Ricin appears to be of potential therapeutic use for killing cancer cells. However, castor-bean products are tested for absence of ricin, so you don’t have to worry too much when you see castor oil listed as an ingredient in your skincare products.
Further reading
Polito, L., Bortolotti, M., Battelli, M. G., Calafato, G., & Bolognesi, A. (2019).Ricin: An Ancient Story for a Timeless Plant Toxin. Toxins, 11(6),324. https://doi.org/10.3390/toxins11060324
