Tuesday, May 29, 2012

Prontosil and Sulfonamides

In 1935, Gerhard Domagk, a German bacteriologist, found that the dye Prontosil inhibited the growth of streptococci in man. However, although it was effective in treating infections, it was without effect on bacteria in vitro. It was soon discovered that Prontosil was degraded in the body and that its active antibacterial component in man was sulfanilamide. This discovery gave rise to a class of chemotherapeutic agents, the sulfonamides, which inhibit the growth of streptococci by preventing their synthesis of the vitamin folic acid in the bacteria. In the normal course of synthesis, p-aminobenzoic acid is fitted into the folic acid molecule. Sulfanilamide, being structurally similar to p-aminobenzoic acid, usurps its place; this opened the way to a major principle of drug design, the concept of antimetabolites.