Ricinus communis Linn. commonly called castors belonging to the family Euphorbiaceae. Ricin is a natural toxin contained in castor seeds. The glycosylated protein comprising two round polypeptide chain A, and chain B is connected by a disulphide bond. Its ability toxicity by inhibiting protein synthesis. Termination of protein synthesis is not the only cause of cell death caused by ricin but some reports indicate the induction of cell apoptosis as well. The ricin chains of A and the most commonly used modifications to make immunotoxin by incorporation with monoclonal antibody therapy (moAbs), form Ricin immunotoxin (R-immunotoxin). Therefore the target of ricin conjugated antibodies is cancer cells and has been studied as an immunotherapy agent.