castor beans

HERMES TRINCIASTOCCHI CASTOR Serie / / Distribucion FRUMACO Chile

Comments

Watanabe

Ricin (n.) = A toxic protein extracted from a castor beans; used as a chemical reagent; can be used as a bioweapon.

Sakamoto

.at.AlexandriaMBaca Merely an observation, I did just buy castor beans for a piece on ricin though. Very easy to get them.

Jackson

2011 castor bean & fall scenes

Yamada

Castor.flv

Peterson

Castor Oil Plant

Young

11. Ricin: A Deadly Protein

The active poison in castor seeds is ricin (RYE-sin), a very deadly protein called a lectin. Ricin is found in the meal or cake after the oil has been extracted. Those who occasionally take castor oil may be assured that ricin does not occur in the pure oil. When a gram of ricin is compared with equivalent weights of other toxic substances, it turns out to be one of our deadliest natural poisons. It has been estimated that, gram for gram, ricin is 6,000 times more poisonous than cyanide and 12,000 times more poisonous than rattlesnake venom. Ricin mixed with food and used as bait is highly toxic to certain pest animals, such as some rodents and insects. E. A. Weiss (1971) states that a dose of 0.035 milligram (approximately one millionth of an ounce) may kill a man, and even small particles in open sores and in the eyes may prove fatal. According to the Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (1997), a dose of ricin weighing only 70 micrograms or two millionths of an ounce (roughly equivalent to the weight of a single grain of table salt from a salt shaker) is enough to kill a 160 pound person. As few as four ingested seeds can cause death in an adult human, and lesser amounts may result in symptoms of poisoning, such as vomiting, severe abdominal pain, diarrhea, and convulsions. Of course the degree of poisoning depends upon the amount ingested and the age and general health of the individual. There are numerous documented cases of ricin poisoning and death when horses, livestock, and poultry accidentally ate castor seeds or meal.

With the exception of certain pathogenic bacteria, lectins include some of the most insidious plant toxins affecting people. In addition to ricin from castor bean seeds, another very poisonous lectin called abrin occurs in the seeds of rosary bean (Abrus precatorius), a common tropical vine in the Legume Family (Fabaceae). According to the Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals, 1983), one thoroughly masticated seed of rosary bean can cause fatal poisoning. Brightly colored rosary beans are commonly strung for seed jewelry in Mexico and Central America. Sometimes the seeds are boiled in order to facilitate the piercing of their hard seed coats, and this heating would undoubtedly denature the toxic proteinaceous lectins inside. Of course, the undisputed record for the deadliest natural toxin goes to the anaerobic bacterium of spoiled food (Clostridium botulinum). A fascinating article on botulism appeared in Scientific American, April, 1968. So deadly is the toxin (even deadlier than strychnine, arsenic and snake venoms), that an amount equal to the weight of ink in a printed period in a textbook is enough to kill 30 adult humans. One ounce could theoretically kill 30 million tons of living matter and one pound could kill the entire human population. However, even an innocuous coconut can be a lethal weapon if you stand under a heavily laden palm. The odds of this unfortunate event is considerably greater than winning the jackpot in the California State Lottery. [In fact, the chance of being struck by lightning is actually greater than winning the California Lottery.]

The poisoning mechanism of castor beans is very complicated. It causes clumping (agglutination) and breakdown (hemolysis) of red blood cells, hemorrhaging in the digestive tract, and irreparable damage to vital organs such as the liver and kidneys. It is most toxic when taken intravenously or inhaled as fine particles. In fact, the possibilities of ricin dust in chemical warfare are horrendous. There are even documented cases of castor bean poisoning in murders by paid assassins.

At the cellular level, ricin is known as a "ribosome-inactivating protein" or Type 2 RIP, one of the most potent cytotoxins in nature. It is synthesized in the endosperm cells of maturing seeds. Ricin is composed of two complex 3-dimensional molecular subunits, a 267 amino acid globular protein called the A chain (RTA) and a 262 amino acid protein called the B chain (RTB). The two polypeptides are held together by a single disulphide bond. The RTA and RTB proteins do not become deadly until the disulsulfide bond is broken and they are separated from each other. Once inside the cell, RTA becomes a deadly enzyme that catalyzes the depurination (loss of purine bases) from ribosomes. When ribosomes lose specific purine bases, such as adenine, they no longer function and protein synthesis shuts down.

In summary, ricin is a potent cytotoxic protein is that is lethal to eukaryotic cells by inactivating the organelle sites of protein synthesis called ribosomes. Just one single ricin molecule that enters the cytosol of a cell (the semifluid medium between the nucleus and plasma membrane) can inactivate over 1,500 ribosomes per minute and kill the cell.

The agglutination of red blood cells has been atributed to a powerful hemagglutinin in castor beans called ricinus communis agglutinin (RCA) and not ricin. Ricin is a potent cytotoxin but a weak hemagglutinin. Poisoning by the ingestion of castor beans is due to ricin, not RCA, because RCA does not penetrate the intestinal wall, and does not affect red blood cells unless given intravenously. If RCA is injected into the blood, it will cause the red blood cells to agglutinate and burst due to hemolysis.

For More Information:
Robertus, J.D. 1991. "The Structure and Action of Ricin, A Cytotoxic N-glycosidase." Seminar in Cell Biology 2: 23-30.
Vitetta, E.S. and P.E. Thorpe. 1991. "Immunotoxins Containing Ricin or its A Chain." Seminar in Cell Biology 2: 47-58.
Wiley, R.G. and T.N. Oeltmann. 1991. "Ricin and Related Plant Toxins: Mechanisms of Action and Neurobiological Applications." In: Handbook of Natural Toxins (Vol. 6). Edited by R.F. Keeler and A.T.Tu. Marcel Dekker, Inc., New York.