Ricinus CommunisRicinus Communis

Toxic PlantsToxic Plants

INTRODUCTIONINTRODUCTION

The seeds from the castor bean plant, The seeds from the castor bean plant, Ricinus communisRicinus communis, are poisonous to , are poisonous to people, animals and insects. One of the people, animals and insects. One of the main toxic proteins is "ricin", named by main toxic proteins is "ricin", named by Stillmark in 1888 when he tested the Stillmark in 1888 when he tested the beans extract on red blood cells and beans extract on red blood cells and saw them agglutinate. saw them agglutinate.

Now we know that the agglutination Now we know that the agglutination was due to another toxin that was also was due to another toxin that was also present, called RCA (Ricinus communis present, called RCA (Ricinus communis agglutinin). Ricin is a potent cytotoxin agglutinin). Ricin is a potent cytotoxin but a weak hemagglutinin, whereas but a weak hemagglutinin, whereas RCA is a weak cytotoxin and a powerful RCA is a weak cytotoxin and a powerful hemagglutinin.hemagglutinin.

Poisoning byPoisoning by ingestioningestion of the of the castor bean is due tocastor bean is due to ricinricin, , not not RCA, because RCA does not RCA, because RCA does not penetrate the intestinal wall, and penetrate the intestinal wall, and does not affect red blood cells does not affect red blood cells unless given intravenouslyunless given intravenously. . If RCA If RCA is injected into the blood, it will is injected into the blood, it will cause the red blood cells to cause the red blood cells to agglutinate and burst by hemolysisagglutinate and burst by hemolysis. .

EtiologyEtiology

Ricin is a powerful protein toxin found in Ricin is a powerful protein toxin found in the castor plant, the castor plant, Ricinus communisRicinus communis. Ricin . Ricin is present in all parts of the plant but is is present in all parts of the plant but is particularly concentrated in the seeds. The particularly concentrated in the seeds. The toxin could be used as a biological toxin could be used as a biological weapon. Purified toxin can be found in a weapon. Purified toxin can be found in a crystalline form, as a dry lyophilized crystalline form, as a dry lyophilized powder, or dissolved in liquid. Ricin acts powder, or dissolved in liquid. Ricin acts by inhibiting protein synthesis.by inhibiting protein synthesis.

Ricin consists of two distinct Ricin consists of two distinct proteinprotein chains chains (almost 30(almost 30kDakDa each) that are linked to each each) that are linked to each other by other by disulfide bonddisulfide bond::

Ricin ARicin A is toxic to the is toxic to the cellcell by interfering with by interfering with Ribosomes, responsible for RNA synthesis Ribosomes, responsible for RNA synthesis

Ricin BRicin B is important in assisting ricin A's entry is important in assisting ricin A's entry into a cell by binding with a cell surface into a cell by binding with a cell surface component. component.

Many plants such as barley have the A chain but Many plants such as barley have the A chain but not the B chain. Since people do not get sick not the B chain. Since people do not get sick from eating large amounts of such products, ricin from eating large amounts of such products, ricin A is of extremely low toxicity A is of extremely low toxicity if and only if the B if and only if the B chain is not present.chain is not present.

TransmissionTransmission

Ricin is very toxic by several routes of exposure, Ricin is very toxic by several routes of exposure, including inhalation, ingestion and injection. including inhalation, ingestion and injection. Most natural exposures occur by ingestion. In Most natural exposures occur by ingestion. In mice, this is the least toxic route, as all of the mice, this is the least toxic route, as all of the toxin is not absorbed from the intestinal tract. toxin is not absorbed from the intestinal tract. Intact seeds have a hard coat and generally Intact seeds have a hard coat and generally pass through the intestine without releasing toxic pass through the intestine without releasing toxic quantities of ricin; the toxin is released if the quantities of ricin; the toxin is released if the seeds are chewed or the seed coat is damaged.seeds are chewed or the seed coat is damaged.

Inactivation/ DecontaminationInactivation/ Decontamination

Ricin can be inactivated by heat; it should Ricin can be inactivated by heat; it should be heated to 80°C for 10 minutes or to be heated to 80°C for 10 minutes or to 50°C for approximately one hour at pH 50°C for approximately one hour at pH 7.8. A 0.1% sodium hypochlorite solution 7.8. A 0.1% sodium hypochlorite solution is also said to be effective, although some is also said to be effective, although some authorities recommend 0.5% sodium authorities recommend 0.5% sodium hypochlorite.hypochlorite.

Incubation PeriodIncubation Period After ingestion, the incubation period is a After ingestion, the incubation period is a

few hours to a few days. After inhalation, few hours to a few days. After inhalation, the incubation period appears to be less the incubation period appears to be less than 8 hours; humans who were than 8 hours; humans who were accidentally exposed to sublethal doses accidentally exposed to sublethal doses developed symptoms in 4 to 8 hours.developed symptoms in 4 to 8 hours.

Perhaps just Perhaps just one milligramone milligram of ricin can kill of ricin can kill an adult. an adult.

The symptoms of human poisoning begin The symptoms of human poisoning begin within a few hours of ingestion. within a few hours of ingestion.

The symptoms are:The symptoms are:

abdominal pain abdominal pain vomiting vomiting diarrhea, sometimes bloody. diarrhea, sometimes bloody. Within several days there is:Within several days there is: severe dehydration, severe dehydration, a decrease in urine, a decrease in urine, and a decrease in blood pressure. and a decrease in blood pressure. If death has not occurred in 3-5 days, the victim If death has not occurred in 3-5 days, the victim

usually recovers. usually recovers.

Clinical SignsClinical Signs

Clinical signs after ingestionClinical signs after ingestion Natural infections generally occur by ingestion. Natural infections generally occur by ingestion.

The ingested toxin usually causes The ingested toxin usually causes severe severe gastrointestinal signsgastrointestinal signs. The symptoms may . The symptoms may include abdominal pain, diarrhea, fever, nausea, include abdominal pain, diarrhea, fever, nausea, vomiting, incoordination, drowsiness and vomiting, incoordination, drowsiness and hematuriahematuria. The fluid loss can lead to . The fluid loss can lead to dehydration, particularly in children. Vascular dehydration, particularly in children. Vascular collapse and death can occur quickly, but most collapse and death can occur quickly, but most patients who survive for 3 to 5 days recover.patients who survive for 3 to 5 days recover.

Clinical signs after aerosol Clinical signs after aerosol exposureexposure

The symptoms of toxicity appear acutely The symptoms of toxicity appear acutely after aerosol exposure; the clinical signs after aerosol exposure; the clinical signs may include fever, tightness of the chest, may include fever, tightness of the chest, cough, dyspnea, nausea and arthralgia. In cough, dyspnea, nausea and arthralgia. In sublethal cases, profuse sweating sublethal cases, profuse sweating occurred several hours later, followed by occurred several hours later, followed by recovery. Lethal human exposures by recovery. Lethal human exposures by aerosol have not been reported. aerosol have not been reported.

Based on studies in laboratory animals, Based on studies in laboratory animals, airway necrosis and pulmonary edema airway necrosis and pulmonary edema would probably develop within 24 hours. would probably develop within 24 hours. Severe respiratory distress and death from Severe respiratory distress and death from respiratory complications and circulatory respiratory complications and circulatory collapse would be expected to occur within collapse would be expected to occur within 36 to 72 hours. The symptoms would most 36 to 72 hours. The symptoms would most likely include dyspnea, cyanosis and likely include dyspnea, cyanosis and hypotension.hypotension.

Ricin was used to assassinate Georgi Markov in 1978, a Bulgarian journalist who spoke out against the Bulgarian government. He was stabbed with the point of an umbrella while waiting at a bus stop near Waterloo Station in London. They found a perforated metallic pellet embedded in his leg that had presumably contained the ricin toxin.

Castor oilCastor oil Castor beans are pressed to extract castor Castor beans are pressed to extract castor

oil which is used for medicinal purposes. oil which is used for medicinal purposes. Ricin does not partition into the oil Ricin does not partition into the oil because it is water-soluble, therefore, because it is water-soluble, therefore, castor oil does not contain ricin, provided castor oil does not contain ricin, provided that no cross-contamination occurred that no cross-contamination occurred during its production. during its production.

Treatment and VaccinationTreatment and Vaccination

Treatment is supportive. Depending on the route Treatment is supportive. Depending on the route of exposure, it may include respiratory support of exposure, it may include respiratory support and treatment for pulmonary edema, or gastric and treatment for pulmonary edema, or gastric lavage and cathartics to remove the toxin from lavage and cathartics to remove the toxin from the digestive system. the digestive system.

Vaccines and antisera are not currently Vaccines and antisera are not currently available, but have been promising for aerosol available, but have been promising for aerosol exposures in experimentally infected animals. A exposures in experimentally infected animals. A protective mask is currently the best form of protective mask is currently the best form of protection from aerosol exposure; the eyes protection from aerosol exposure; the eyes should also be protected whenever possible.should also be protected whenever possible.

Morbidity and MortalityMorbidity and Mortality

More than 750 cases of accidental or More than 750 cases of accidental or deliberate poisoning have been described deliberate poisoning have been described in humans. The symptoms and outcome in humans. The symptoms and outcome depend on the dose and route of depend on the dose and route of exposure. By ingestion, two and a half to exposure. By ingestion, two and a half to 20 seeds is a lethal dose, with children 20 seeds is a lethal dose, with children more susceptible than adults to small more susceptible than adults to small quantities of seeds.quantities of seeds.