A naturally occurring antioxidant dicatechol originally derived from the creosote bush Larrea divaricatta with antipromoter, anti-inflammatory, and antineoplastic activities. Masoprocol directly inhibits activation of two receptor tyrosine kinases (RTKs), the insulin-like growth factor receptor (IGF-1R) and the c-erbB2/HER2/neu receptor, resulting in decreased proliferation of susceptible tumor cell populations. This agent may induce apoptosis in susceptible tumor cell populations as a result of disruption of the actin cytoskeleton in association with the activation of stress activated protein kinases (SAPKs). In addition, NDGA inhibits arachidonic acid 5-lipoxygenase (5LOX), resulting in diminished synthesis of inflammatory mediators such as prostaglandins and leukotrines; it may prevent leukocyte infiltration into tissues and the release of reactive oxygen species and, at higher concentrations, may also inhibit cyclooxygenase. or A drug put on the skin to treat growths caused by sun exposure. A form of masoprocol that is taken by mouth is being studied in the treatment of prostate cancer. Masoprocol is an antioxidant, and it may block certain enzymes needed for tumor growth. Also called Actinex, NDGA, and nordihydroguaiaretic acid.