Capitulo del Libro: Toxic Constitutents of Plant Foodstuffs.
I.E. Liener, editor Academic Press Inc. New York, 1969
The extracts of many plants have the property to agglutinate red blood cells caused by some remarkable proteins called «phytohemagglutinins» or «lectins.» * They are found mostly in seeds from which they may be extracted by water or salt solution; they may also exist in leaves, bark, roots, tubers, latex, etc. Agglutinin-containing plants have been found in many botanical groups including mono- and dicotyledons, molds and lichens, but most frequently they have been detected in Leguminosae and Euphorbiaceae (Tobiska, 1964).
The first description of a phytohemagglutinin was given by Stillmark (1889), who studied the toxicity of castor beans and press cake from the production of castor oil. From his very thorough investigation he conc1uded that the toxic action was due to a protein which he called «ricin» and which he showed to be capable of agglutinating the red cells from human and animal blood.
Several other toxic plant proteins have been described in the following years after the discovery of ricino Many have never been studied in much detail. The relative facility with which the castor beans can be obtained and the strong toxicity of ricin were probably the’ reason why more investigators were attracted to this rather than to similar but less easily available plants.
The early literature on the toxicological properties of the plant hemagglutinins has been reviewed by Ford (1913) and Brocq-Rousseu and Fabre (1947). More recent reviews emphasizing the physicochemical properties and nutritional significance of the phytagglutinins may be found in papers by Liener (1962, 1964).
The first antitoxins were prepared using ricin and abrin, the toxin from the seeds of Abrus precatorius by Ehrlich (189la,b). He not only demonstrated the neutralizing action of the serum of mice immunized against these toxins when mixed with a solution of the corresponding seed extract, but also the specificity of this reaction because antiricin serum would not act on abrin and vice versa.