Resource: Nature's Pharmacy

In recent years, newspapers have run countless stories of athletes using steroids to enhance their performance on the track or field and to speed recovery from injury. But steroids are not illicit concoctions prepared on the sly in hidden laboratories. Rather, they are natural compounds, manufactured largely by biochemical companies to treat bona fide medical conditions including arthritis and sex hormone deficiency. You might be surprised to learn that the bases for steroids and many other natural compounds used to help treat human illnesses originate in plants.

In the early 20th century, chemists began to find structural similarity among a large group of natural substances found in humans and other mammals, including cholesterol, bile acids, and sex hormones. Although the medicinal potential of these compounds quickly became obvious, extracting sufficient quantities of these substances from animal tissue and fluids was very expensive. So the burden fell on chemists to create synthetic substitutes.

Investigations revealed that certain plant compounds contain a structural and functional similarity to human compounds that produce a sought-after physiological response—such as shutting down pain receptors. Once these chemical compounds could be isolated from the plant and their molecular structures analyzed, chemists could replicate them in the lab. Plant sources held tremendous promise for medicine because active compounds could be extracted from plants in far greater quantities at a far lower cost.

While plants and animals share few physical similarities, they are very similar at the cellular level. All living things produce chemical compounds as part of their normal metabolic activities. Using a similar pathway from species to species, primary metabolism—also called basic metabolism—produces all products that are essential for cell growth and development. Examples of primary metabolites are sugars and fats. Secondary metabolism produces molecules that are not important for the survival of the cell, but are important for the survival of the entire organism. In plants, secondary metabolites include flower colors and scents that attract pollinators, as well as toxic components that ward off predators. It is these secondary metabolites that can produce therapeutic effects in humans and that can be refined to produce drugs.

Today, it's widely known that the natural world is full of examples of chemical compounds and enzymes vital in the manufacture of medicines. Biomining is the process of seeking organisms for the purpose of exploiting their natural products for drug development and other uses. The focus is on identifying new secondary metabolites in plants, bacteria, fungi, and many marine organisms. The possibility that previously undiscovered plants could have these vital compounds—for example, plants that grow in dense, unexplored regions of rainforest and undersea—is a driving argument for preserving biodiversity.

To learn more about the steps a chemist uses to tailor organic molecules, check out Build a Steroid.

To learn more about the molecular structure of organic molecules, including alkaloids and steroids, check out Ringed-Carbon Compounds.

To learn about chemist Percy Julian and his pioneering work synthesizing organic compounds to create important therapeutics, check out Synthesizing an Alkaloid and Synthesizing a Steroid.

• Have you ever seen a foxglove plant? Do you think it is likely that other medicinal substances from plants will be discovered? What factors make it more or less likely that this will happen?
• How do you think a scientist goes about finding a plant substance that could be used as a treatment for a specific human condition such as arthritis or cancer?
• What do you think the connections are between the basic metabolisms of plants and humans?
• Are all bacteria harmful to humans?