Ricin – the castor bean poison

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Watching Breaking Bad last night ‘Heisenberg’ proposed extracting a castor bean and poisoning the crazy drug dealing ‘Tuco’. Is this real and what is the science behind it?  What was the James Bond style killing they talked about?


Breaking Bad is my new box set of choice, as suggested to me in the comments of the ‘Christmas gifts‘ blog. I was watching Episode 1 of Series Two and the two main protagonists are in a sticky situation with a crazed methamphetamine dealer named Tuco.  The Chemistry teacher with the pseudonym ‘Heisenberg’ proposes extracting some pulped up castor beans and using that to poison Tuco.  That poison would be ricin.

Ricin is extracted from the bean of the castor plant Ricinus communis (above).  The plant produces nice red flower buds and seed pod, which houses the castor seed.  The plant grows natively in many countries but is also introduced and grows freely in others.  It is available in the UK as a seed or a plant in garden centres, in New Zealand I saw a couple of plants growing by the roadside.  Many people who have memories of swallowing castor oil to ‘keep you regular’ will be surprised to find out the same beans contain a deadly poison.  The process used to produced castor oil does not extract the ricin, or not in any meaningful amount.  The ricin is extracted using solvents after the bean is crushed and the oil is released.  Each bean may contain as much as  5 % ricin by weight, and a fatal dose of ricin can be as low as 1 or 2 milligrams (for comparison of doses an adult dose of paracetamol is 500 to 1000 milligrams). If chewed the seeds may release enough of the poison to be fatal but would not be harmful if swallowed whole.  Ricin is far more lethal when injected or inhaled than eaten.


Ricin is a large protein, of around 60 to 65 kDa size, made up of two roughly equal chains.  As a comparison of protein size the doping agent EPO, mentioned here, is around 34 kDa.  Ricin acts as a protein synthesis inhibitor.  In lay terms this means that the body loses the ability to produce new cells, to complete any enzymes reactions and to control muscle movement.  It is easy to see why that would not take  long to cause death.


The infamous ricin umbrella murder


The most famous case of ricin poisoning was that of the Bulgarian dissident Georgi Markov, murdered in London in September 1978.  Markov was living in exile in the UK.  A prominent playwright and journalist in his native Bulgaria, he had spoken out against the ruling communist regime and was warned he should seek exile in another country.  He fled to London in 1968.  Whilst in London Markov was employed by the BBC World service broadcasting to Bulgaria.  Using his radio shows he continued to comment on communist rule and the Bulgarian government from afar.



One morning on his journey from Waterloo to the World Service he was waiting for a bus on Waterloo Bridge.  A man bumped into him and dropped his umbrella.  Markov mentioned this incident when he arrived at work.  Soon he saw a red welt on his leg where the umbrella had touched and started to feel feverish.  The effects felt by Markov were typical of ricin poisoning.  He felt hot, flushed and nauseous, similar in effect to a flu type bug.


Within a day he had been hospitalised and it was three days until he did in hospital.  No one has still officially claimed responsibility for his death, although the Bulgarian secret police are the most likely contenders, with rumoured help from the KGB.


At post mortem a pellet was recovered (shown left) that had a few small indentations which contained enough ricin to kill.  The pellet had been coated with a wax which melted at body temperature to release the ricin.  An umbrella was recovered at some point which had been modified to include a hollowed out tip and a firing mechanism.  The ricin content was confirmed by the UK Government research facility at Porten Down. A similar attack had taken place in Paris but the victim survived as the wax failed to melt.


The umbrella is now held at the Metropolitan Police ‘Black Museum’ at New Scotland Yard.  I was fortunate enough see the umbrella on a visit the museum as a student during the late 1990s, when the museum was not open to the general public.  For several years I then worked near to Waterloo and every time I crossed the bridge or waited at a bus stop I was on the lookout for umbrellas!


Can it be treated? And how to detect ricin


Clinically there is little than can be done to remove ricin from the body once absorbed into the blood.  Supportive treatment of the symptoms may be all that is possible.

There are many methods, particularly immunometric to detect ricin in blood or urine samples. More recently analytical methods involving mass spectrometry have been published which can detect both ricin and a small molecule ricinine which is also from the castor bean.  I was previously been involved in method development for a method to detect ricinine in human samples using GC-MS, but that is for another day perhaps.


I’ll not ruin the Breaking Bad plot by telling you what happens next to Tuco!


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Bean photo Ricinus communis, Euphorbiaceae, Castor Oil Plant, seeds, by H Zell, Wikimedia commons.  Plant photo and pellet photo have been on my hard drive for ages, if anyone owns them please let me know and I will put a credit up for them!

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About Dr Tom Bassindale

Dr Tom Bassindale is a forensic scientist, and the founder of We Are Forensic. He is currently the subject lead for chemistry and forensic science at Sheffield Hallam University. He's managed hundreds of forensic toxicology cases, and is an experienced court witness. He has specialist expertise in forensic toxicology and drug testing in sport. And yes... he watches CSI.