Part 6: Phytochemistry—Plant Secondary Metabolism

Secondary metabolites are a diverse class of compounds made by plants that serve many important functions. Unlike primary metabolites, these compounds are not essential for a plant’s basic metabolism, but still play significant roles in allowing the plant to adapt to and thrive in its environment. Since plants lack some fundamental features found in humans and animals, they must have a way to handle these extra challenges. For instance, plants do not have an immune system to get rid of disease-causing microbes, they cannot actively seek out a mate, they cannot run or hide to escape from predators, and they do not have a skeletal structure to protect them from injury. Secondary metabolites provide solutions to all of these problems and many others. Collectively, all plants produce over 100, 000 different varieties of secondary compounds that accomplish a myriad of purposes.

The main categories of secondary metabolites are terpenes and terpenoids, phenolics, and alkaloids. Compounds are grouped into one of these categories based on their chemical structure.