Ricin

The protein ricin (pronounced [ˈraɪsɪn]) is a toxin from the castor bean (Ricinus communis). Ricin can be extracted from castor beans and is known to have an average lethal dose in humans of 0.2 milligrams (1/5,000th of a gram), though some sources give higher figures.[1] It is considered to be twice as deadly as cobra venom. The 2007 Guinness World Records Book considers ricin the world's most potent plant toxin.[