Antibiotics. Gardeners with black walnut trees know
that the tree’s roots can have an allelopathic effect on nearby vegetation. Juglone,
a substance in the tree's roots, inhibits the growth of many other types of plants. Antibiotics are another example of allelopathy. The effectiveness
of antibiotics depends on the fact that the presence of one organism can inhibit the
growth of another organism. We want our antibiotics to kill—or at least inhibit the
growth of—certain disease-causing microorganisms. Yet they must be harmless to other
organisms—namely, us!
As early as 2000 B.C., the Chinese were said to have
applied green mold to relieve skin ulcers. In 1877, Pasteur and Jaubert observed that
anthrax bacteria were destroyed by other microorganisms. But the real breakthrough came in
1928, when Sir Alexander Fleming noted that a specific green mold, Penicillium, had
contaminated the bacteria cultures he had been growing in his lab. The discovery of
penicillin was the result of Fleming’s astute observation that this
"contaminant" was destroying the disease-causing bacteria he was culturing.
Aspirin. In the 5th century B.C.,
Hippocrates, a Greek physician, discovered that chewing on willow bark relieved pain. He
began using powdered willow bark to lower fevers and ease the pain of childbirth.
Fast-forward to the mid-1700s, when the beneficial
properties of willow bark were once again "discovered." The active substance was
determined to be salicin, or salicylic acid. (Salicin is a derivative of the Latin word Salix,
which is the genus name of willows.) Willows (and a number of other plants) produce
salicylic acid, most likely as part of a defense against infection.
It was soon found that salicylic acid on its own caused
stomach upset. However, combining it with acetyl chloride produced a less irritating
product. Eventually manufacturers began using spirea as the source of salicylic acid. The
name aspirin is derived from the words Acetyl chloride and SPIRea.
Today aspirin is used to relieve pain and reduce
inflammation. Because it interferes with blood clotting, it is believed to cut down on the
risk of heart disease and increase the survival rate for heart attack victims. New
research indicates that it may also reduce the risk of colorectal cancer.
