The Ergot Alkaloids

THE ERGOT ALKALOIDS

Ergot alkaloids are produced by Claviceps purpurea, a fungus that infects grasses and grains—especially rye—under damp growing or storage conditions. This fungus synthesizes histamine, acetyl-choline, tyramine, and other biologically active products in addi-tion to a score or more of unique ergot alkaloids. These alkaloids affect α adrenoceptors, dopamine receptors, 5-HT receptors, and perhaps other receptor types. Similar alkaloids are produced by fungi parasitic to a number of other grass-like plants.

The accidental ingestion of ergot alkaloids in contaminated grain can be traced back more than 2000 years from descriptions of epidemics of ergot poisoning ( ergotism). The most dramatic effects of poisoning are dementia with florid hallucinations; pro-longed vasospasm, which may result in gangrene; and stimulation of uterine smooth muscle, which in pregnancy may result in abortion. In medieval times, ergot poisoning was called St. Anthony’s fire after the saint whose help was sought in reliev-ing the burning pain of vasospastic ischemia. Identifiable epi-demics have occurred sporadically up to modern times (see Box: Ergot Poisoning: Not Just an Ancient Disease) and mandate con-tinuous surveillance of all grains used for food. Poisoning of graz-ing animals is common in many areas because the fungi may grow on pasture grasses.

In addition to the effects noted above, the ergot alkaloids pro-duce a variety of other central nervous system and peripheral effects. Detailed structure-activity analysis and appropriate semi-synthetic modifications have yielded a large number of agents of experimental and clinical interest.