Phorbol Ester

**Semantic type:** Hazardous or Poisonous Substance|Organic Chemical

**Definition:** Polycyclic compound isolated from croton oil in which two hydroxyl groups on neighboring carbon atoms are esterified to fatty acids. The commonest of these derivatives is phorbol myristoyl acetate (PMA). Potent co carcinogens or tumor promotors, they are diacyl glycerol analogs and activate protein kinase C irreversibly.