At a young age, we are taught in school that all living organisms are born, grow, reproduce, and die. As simple as that. So naturally, to carry out these vital functions, the metabolism of every living organism must be equipped to provide nutrients and chemicals either by consuming nutrients from the environment (e.g. digesting the delicious bowl of pasta I just devoured to obtain essential amino acids), or by synthesizing chemicals (e.g. producing nonessential amino acids). These molecules resulting from our metabolism are called metabolites. When metabolites are synthesized to support growth, development or reproduction of an organism, they are called primary metabolites.
(NOTE: to keep things simple, let’s leave the whole dilemma around whether viruses are living organisms or not out of this post.)
You may have already inferred that the classification of these metabolites as “primary” indicates that there are more types of metabolites, which is right!
Life is complex, and metabolisms are beautiful machineries that do much more than the bare minimum. The metabolic pathways in our cells not only allow us to survive, they allow us to live fully! The biochemical stimuli in our cells tell us our bodies need food, so we get hungry (and often hangry…), and once we’ve had our meal there is more stimuli to make us feel happy about it and sleepy to allow our bodies to digest the nutrients they just got (or as my people would call it, el mal del puerco).
Many organisms, including bacteria, fungi, plants and animals, produce secondary metabolites. Secondary metabolites satisfy functions that allow us to stay balanced; or in other words, maintain homeostasis. Many of the popular superfoods got this title due to their abundance in particular secondary metabolites, such as antioxidants, flavonoids and other phenolic compounds.
There is a group of secondary metabolites, however, that have become the center of attention over the past few months: cannabinoids.
These chemicals are often discussed in the context of their incredible potential as therapeutic drugs, but we don’t hear much about their originally intended purpose. Why did the Cannabis plant start to produce cannabinoids in the first place?
Photo by Patrick Tomasso on Unsplash
Plants produce secondary metabolites for various reasons, mostly as a response to stress, which is a bit ironic as many people consume Cannabis to deal with stress. Regardless…for plants, stress can come in many forms, such as drought, lack of nutrients, too much sunlight (UV light), and pathogen exposure, to name a few.
In 2017, Jonathan Gorelick and Nirit Bernstein authored an excellent chapter in the book “Cannabis sativa L.- Botany and Biotechnology”, which summarizes many studies providing evidence to the environmental factors influencing cannabinoid production in the plant. Gorelick and Bernstein discuss studies in the 70’s showing a correlation between high amounts of macronutrients and an increase in THC content in the plant. They also discuss a study in 2012 where THC content increased after exposure to UV light (likely due to an increase in floral material and not necessarily due to an increase in THC synthesis), and three studies between 1977 and 2003 talking about the insecticide and insect deterrent potential of THC, suggesting the role of cannabinoids in plants as a protection against insects. Similarly, they included studies from 1984 and 2009 discussing the antimicrobial role of cannabinoids, which suggests that cannabinoids also play a role in protecting the plant from microbial pathogens; they also discuss studies from the 70’s showing an increase in trichome density in dry conditions, and even a couple of studies from the 80’s discussing that cultivation of hemp in dry environments (a variety known for its lack of THC) produced a significant amount of this cannabinoid.
This very long and dense paragraph illustrates the following: most studies we have on the matter are more than 10 years old. Of course, I do not claim to have read every single publication out there on the topic, but even if there are more scientific publications that provide evidence to the role of cannabinoids in the plant, they are not easily accessible.
Yes, we have some knowledge on the role that cannabinoids play in defense against insects and microbes, as well as UV irradiance. These roles are attributed to the little hairs present in leaves and flowers of many plant species, called trichomes, and I don’t think Cannabis should be any different. However, we do not know many details about these mechanisms. Why are there more than 70 different cannabinoids in the plant? What triggers cannabinoid synthesis in the plant? Does pathogen recognition trigger cannabinoid production? Does the plant synthesize different cannabinoids depending on the particular species of the insect or microbe attacking it? Are there symbiotic associations that stimulate cannabinoid synthesis?
There are so many questions to which answers are not easily available, and in this day and age it should be quite easy to find all sorts of information, so maybe we have not figured them out yet.
We talk about the need to characterize the pharmacological activity of cannabinoids, which I consider crucial for the success of this emerging industry, but I also believe it is equally important to effectively understand the role of cannabinoids in the context of the plant. If we do not understand why plants need to get high, we might not be getting the full picture.