Ch. 10: Wonder Drugs


For thousands of years, medicinal herbs have been used to treat a variety of ailments such as wounds, sickness, and to relieve pain. But none of these herbal remedies could do anything for infection. The use of Phenol as an antiseptic prevented the actual contraction of infectious bacterium, but once the infection was in your body, it was practically a death sentence. For this reason, antibiotics were developed through a process of trial and error. In the early 1930's, Gehard Dogmark discovered the use of prontosil red dye as an antibacterial agent. When prontosil red enters the body, it breaks down into sulfanilamide, which was the active bacteria fighting ingredient of the prontosil red molecule. Once it was discovered that sulfanilamide was the molecule responsible for the antibacterium properties, the structure of this molecule was changed many times in hopes that it would make the drug more effective. The resulting molecules are all part of the family of antibiotics that came to be known as sulfanilamides of sulfa drugs. Sulfa drugs were found to be very effective against infections such as pneumonia, scarlet fever, and gonorrhea, but they also had a long list of side effects including an allergic response, rashes, fever, and kidney failure. The size and shape of the sulfanilamide molecule prevents bacteria from making an essential nutrient, folic acid. Folic acid is made from a smaller molecule, p-Aminobenzoic. The chemical structures of p-Aminobenzoic and sulfanilamide are so similar that bacteria will mistake sulfanilamide for p-Aminobenzoic and use sulfanilamide in its place. The bacteria then, are unable to make enought folic acid, and die. Humans are not affected by the sulfanilamide because our source of folic acid comes from our food and is not made within our bodies.(Le Couteur & Burreson 181-200)

In 1877, Louis Pasteur, discovered penicillin. This mold is so important because it was nontoxic, nonirritating, had none of the side effects of the sulfa drugs and could be applied directly to the tissue. Penicillin is effective because of the shape of its molecule. Penicillin's structure contains a four member ring in which the bonds form a square, and consequently 90 degree bond angles. When the penicillin encounters bacterial, the four membered ring opens and effectively deactivates the an enzyme that creates the cell wall. Without the ability to grow cell walls, growth of new bacteria is severely inhibited. (Le Couteur & Burreson 181-200)

Molecular Structure of Penicillin