Plant-based pharmaceuticals: A peek inside nature’s apothecary

Pharmacists’ inspiration in nature

Through the synthesis of artificially designed drugs it appears as if the current pharmaceutical production is fundamentally detached from natural medicine. While this might seem the case, it is not the reality. Nature has both provided and inspired many pharmaceutical products and continues to do so even to this day.

According to the United States Department of Agriculture (USDA) a full 40% of all the medical drugs available in the western world come directly from plants or have a chemical structure derived from a naturally occurring plant compound. This percentage also includes the current top 20 bestselling prescription drugs in the United States.

These plant-based pharmaceuticals usually fall under the definition of secondary metabolites. Secondary metabolites are chemical compounds produced by living organisms that are not directly involved in the normal growth, development, or reproduction of that organism, but are rather involved in mediating ecological interactions. For example, many plants contain several chemical compounds that are toxic to certain strains of bacteria, fungi or even animals and are thus thought to be a defense against potential pathogens or predators. These compounds are not strictly necessary for the plant's existence, but they are useful in preventing damage caused by other species, therefore mediating ecological interactions. You can learn more about secondary metabolites here.

With this post, we begin our path of imparting knowledge on how plant-based medications are produced, what plants and plant-based chemicals are useful, and the entire science behind it.

A closely-knit world

Why is it that certain plant secondary metabolites are able to exert a pharmacological function in the human body? Despite it is far from a settled debate, a partial explanation could be found in the ‘xenohormesis hypothesis’. Xenohormesis is the biological principle that states that certain secondary metabolites produced by plants can alter some functions in the animals who consume them, providing them with enhanced stress resistance or other survival benefits.

Animals, for that matter, could take advantage of a plant’s sophisticated stress response to sense changes in their environment. Despite the fact that this idea describes several chemical actions of plant-derived compounds, such as those known to effectively activate antioxidant mechanisms in human cells. It however, fails to give a complete explanation for all the pharmacologically active compounds that we can find. For instance, some plant secondary metabolites are simply structurally similar to the compounds found in the human body and can elicit a comparable response. Lastly, some plant compounds with a specific capability, like bactericide or fungicide function in plants, can perform a similar function for an animal that consumes them.

A brief history about plant-based pharmaceuticals

Evidence for the usage of plants for medicinal purposes is thought to date back to prehistoric times. The oldest evidence for such usage can be found in a Neanderthal’s burying site from 60,000 BC containing the remains of valuable medicinal plants.

The first written records, in the form of little clay tablets, come from Mesopotamia and date from about 2600 BC. They describe the usage of several plants, including Cedrus species (cedar), Glycyrrhiza glabra (licorice), Commiphora species (myrrh) and Papaver somniferum (poppy), all of which are still used as the source of important pharmaceutical compounds. For example, enoxolone, a secondary metabolite that is obtained from licorice, has been used to relieve cough symptoms for at least 3500 years and is still used in some cough syrups today.

Similarly, morphine, a molecule present in poppy plants, is one of the most widely used pain relievers of modern medicine. In the early nineteenth century, in the aftermath of Europe's scientific revolution, all accessible information of pharmacologically active plants was gathered and rationalized for the first time. As a result, ‘pharmacognosy’, or the study of medicines or substances derived from natural sources such as plants, microorganisms, and animals, was established. This discipline, whose name is derived from the Greek words ‘pharmakon’ (drug) and ‘gnosis’ (knowledge), was able to describe in a scientific manner the physiological effects of plant-based pharmaceuticals.

Plant-based pharmaceuticals in modern times

With the fast development of chemical synthesis in the late 19^th and throughout the 20^th century, extracting unique plant-derived pharmaceuticals from its original plant was swiftly regarded outdated. Chemical synthesis enabled the production of considerably larger amounts as well as the creation of synthetic medications with increased activity and fewer negative effects. For example, acetylsalicylic acid, the chemical compound behind Aspirin, is a modified form of salicin, a compound found in Salix alba (common willow), that has enhanced pharmacological properties and was originally synthesized by chemical synthesis towards the end of the 19^th century.

However, in recent decades, the idea of extracting medicinal compounds from plants has gained renewed interest. Plants have an exceptional profile for sustainable pharmaceutical production since they are powered by sunlight and require only a few key components for growth and development.

Furthermore, many complex plant-derived pharmaceuticals cannot yet be produced by chemical synthesis or are extremely difficult to synthesize. This is the case for one of the most widely used anti-cancer drugs, taxol, which is found in the inner bark of Taxus brevifolia (Yew Tree). However, growing a whole plant and extracting the compound of interest, on the other hand, is typically both costly and labor intensive. As a result, modern plant-based pharmaceutical production is often carried out using in vitro culture techniques, in which plant cells can be efficiently cultivated in the laboratory or in huge bioreactors and then processed to extract and purify the needed compounds. Thus, nature and technology are intrinsically tied in the production of pharmaceuticals.

For more interesting articles on plant-based industries, keep checking this space.

By David Alzuria Rodríguez | 6-April-2022

About the author

David Alzuria Rodrguez is a Spaniard from Barcelona. He holds a master's degree in plant biotechnology. He recently began performing plant science communication for Lab Associates in the form of short articles about plant-based cosmetics and pharmaceuticals. He has always been fascinated by nature and how it interacts with human societies. As a result, he decided to create an Instagram page, @plant_chem, dedicated to plant secondary metabolites as well as their properties and applications. He enjoys spending his spare time with friends and family, gardening, and hiking in the mountains.

References

• N. Dhami, “Trends in Pharmacognosy: A modern science of natural medicines,” J. Herb. Med., vol. 3, no. 4, pp. 123–131, 2013, doi: 10.1016/j.hermed.2013.06.001.
• A. Gurib-Fakim, “Medicinal plants: Traditions of yesterday and drugs of tomorrow,” Mol. Aspects Med., vol. 27, no. 1, pp. 1–93, 2006, doi: 10.1016/j.mam.2005.07.008.
• M. J. R. Howes et al., “Molecules from nature: Reconciling biodiversity conservation and global healthcare imperatives for sustainable use of medicinal plants and fungi,” Plants People Planet, vol. 2, no. 5, pp. 463–481, 2020, doi: 10.1002/ppp3.10138.
• D. W. Lamming, J. G. Wood, and D. A. Sinclair, “Small molecules that regulate lifespan: Evidence for xenohormesis,” Mol. Microbiol., vol. 53, no. 4, pp. 1003–1009, 2004, doi: 10.1111/j.1365-2958.2004.04209.x.