Isolation of a guanylate cyclase inhibitor from the balsam pear (Momordica charantia abreviata)

The balsam pear (Momordica charantia abreviata) is a plant which grows wild throughout subtropical regions including the Gulf Coast and Florida. The ripe fruit is highly toxic and produces mild hypoglycemia. Preparations of the ripe fruit and the leaves but not the unripe fruit or seeds inhibited guanylate cyclase activity whereas adenylate cyclase activity was unaffected. The guanylate cyclase inhibitor (GCI) has been purified about 30-fold has an estimated molecular weight of 5000 to 50,000 and is acid stable and heat labile. GCI blocked the activation of guanylate cyclase by nitroso chemical carcinogens, and therefore, may be useful in studying mechanisms of chemical carcinogenesis.