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Why can some Fabales seeds be poisonous?
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Fabales
A flowering stalk of yellow partridge pea (Chamaecrista fasciculata) in the eastern United States.
Many seeds within the order Fabales contain secondary compounds that serve as a natural defense mechanism to protect the plant against predators. These chemical substances can be toxic to humans and other animals when ingested.12
The toxicity of these seeds is often attributed to the presence of specific biochemical components, including:
- Phytohemagglutinin: A large protein molecule found in approximately 60 percent of tested Fabales seeds, which can be toxic to rats and has the capacity to agglutinate certain human blood types.1
- Toxic Proteins: Some species, such as the jequirity bean, contain highly potent toxins like abrin, which can be fatal to humans if the seed is chewed and consumed.234
- Amino Acids and Alkaloids: Certain species contain nonprotein amino acids, such as canavanine, or various alkaloids that can cause serious neural or physical harm to both humans and livestock.12
While many members of the family Fabaceae are vital food sources, these chemical defenses are a significant evolutionary trait for the survival of certain species within the order.154