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Module 5: Why Do Plants Make Drugs for Humans?

What do cocaine, nicotine, caffeine, THC (tetrahydrocannabinol), morphine, and aspirin have in common? They all come from plants. Why would plants make these drugs? How do the compounds get out of the plant to cause actions in the body? Plants are the oldest and most widely used source of medicinal drugs. Even today, many drugs are still extracted from plants for use as therapeutic agents or for non-medicinal purposes. And, based on knowledge we have gained about drugs derived from plants, pharmaceutical companies can develop new drugs synthetically that have better efficacy and fewer side effects.

This module will illustrate some basic plant biology, human biology, and chemistry principles by discussing several properties of drugs obtained from plants. Topics include: 1) a discussion of natural selection, 2) a description of the plant classification of Angiosperms and the difference between monocots and dicots, 3) a description of the alkaloid class of chemicals, 4) types of chemical bonds that enable drugs to bind to their targets (proteins such as receptors, enzymes or transporters), and 5) the role of enzymes in metabolism.