Cortisone is a naturally occurring hormone made by the human body's adrenal glands, located just above the kidneys. It is also present in the bile of cattle. In 1948, recognizing cortisone's remarkable effectiveness in shutting down pain receptors, doctors began using cortisone produced from animal bile to treat patients suffering from a debilitating condition called rheumatoid arthritis.

Although some cortisone circulates naturally through the body, large doses of it are needed to treat the symptoms of rheumatoid arthritis. Because millions of people suffered from the condition—and because animal bile yielded precious little cortisone at a very high cost—cortisone was in high demand but short supply. The challenge for scientists was to somehow make a far greater quantity of it at a much lower cost.

The process of making a natural substance in the lab from simple building blocks is called synthesis. In order to synthesize a hormone like cortisone, chemists have to first understand how the natural molecule is put together. Based on its chemical structure, cortisone is classified as a steroid hormone. Although different steroids produce different physiological effects, all steroid molecules have a similar chemical structure: a nucleus composed of three six-sided carbon rings fused to each other, and one five-sided ring. In 1948, the procedure used to synthesize cortisone using animal bile involved 38 steps.

In 1949, the African American chemist Percy Julian pioneered a much simpler approach, one that used a cheap and abundant source—soybeans—in place of animal bile. Working from knowledge established during the 1920s and 1930s, when chemists had discovered that certain plant compounds contained a structural and functional similarity to animal compounds, Julian set out to create a plant-derived compound that would produce the same physiological response in humans as animal-derived cortisone.

Julian succeeded in synthesizing a molecule that, though it wasn’t exactly cortisone, was very similar in its chemical framework. It varied from cortisone by one single oxygen atom. Julian's molecule, known as "Compound S," was also present in the human body. In fact, the body used it to produce natural cortisone in one simple step. Likewise, to make synthetic cortisone from Compound S, one had only to deliver the missing oxygen atom to a precise location on the molecule. Scientists found a way to do this within two years, and cortisone that had previously cost hundreds of dollars a gram could be made for pennies.

Investigate physical and chemical changes in this NOVA classroom activity.

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