Phorbol esters are a class of chemical compounds found in a variety of plants, particularly in the Euphorbiaceae and Thymelaeaceae families. Chemically, they are ester derivatives of the tetracyclic diterpenoid phorbol.
Phorbol esters are known for their ability to promote tumors. In particular, 12-O-tetradecanoylphorbol-13-acetate (TPA) is used as a biomedical research tool in models of carcinogenesis.
Plants that contain phorbol esters are often poisonous.