When you are learning about cannabis it is only a matter of time before you encounter a term called “Entourage Effect” or “Ensemble Effect”. In a nutshell the term encapsulates in a simple phrase the difference between isolated or synthetic cannabinoids such as delta-9 tetrahydrocannabinol (THC) versus the whole cannabis plant which contains hundreds of cannabinoids and bioactive terpenes. The pharmaceutical industry likes to work with single active compounds that can be synthesized, genetically modified and where production can be scaled up by genetically introducing the desired compound into alternative, mostly microbial, hosts as bioreactors. However, over the years more and more evidence has accumulated suggesting that there are real therapeutic and practical benefits of using the whole cannabis plant or plant extracts containing a larger spectrum of the bioactive compounds because there appears to be synergy between the individual active ingredients.
Prof. Raphael Mechoulam is considered by many to be the grandfather of modern cannabis research. His research group first discovered and characterized the main, active ingredient of the cannabis plant, delta-9 tetrahydrocannabinol (THC) in 1964. Mechoulam’s graduate students and post-doctoral researchers subsequently proceeded to deliver major contributions in the field of cannabis science. For example, Mechoulam’s postdocs Lumír Ondřej Hanuš and the late William Devane discovered the first endocannabinoid, which Devane named anandamide, inspired by the hindu word for bliss: “ananda”.
When Devane joined Mechoulam’s research group he was already accomplished in the cannabis science field, as he previously discovered and described the first cannabinoid receptor as part of his Ph.D dissertation in Prof. Allyn Howlett’s laboratory at Saint Louis University School of Medicine in 1988. The discovery of the endocannabinoid anandamide reaffirmed the importance of fatty acid amides and their derivatives. So, in 1992 Devane published a paper in Science suggesting that arachidonylethanolamide might be another promising endocannabinoid candidate. This was confirmed three years later, when another one of Mechoulam’s Ph.D. students, Simon Ben-Shabat identified and characterized the second major endocannabinoid : 2-arachidonoylglycerol (2-AG).
Prof. Raphael Mechoulam's research group kicked off the modern era of cannabis science
While the cannabis plant has been used for medicinal purposes for millennia, this small research group essentially kicked off the modern era of cannabis science and shaped the foundation of our understanding of how cannabis interacts with the human endocannabinoid system. In 1998, three years after the discovery of 2-AG, Prof. Raphael Mechoulam and his Ph.D. student Shimon Ben-Shabat coined the term “Entourage Effect” in a paper published by the European Journal of Pharmacology :
“An entourage effect: inactive endogenous fatty acid glycerol esters enhance 2-arachidonoyl-glycerol cannabinoid activity.” Ben-Shabat, S et al. European journal of pharmacology vol. 353,1 (1998): 23-31. doi:10.1016/s0014-2999(98)00392-6
The research describes the discovery of two endogenous glycerol esters, [2-linoleoyl-glycerol (2-LG) & 2-palmitoyl-glycerol (2-PG)] which were able to amplify the activity of the endocannabinoid 2-AG by inhibiting its metabolic breakdown. In other words, they showed synergy with 2-AG without directly binding to the cannabinoid receptors or showing any behavioral activities in the animal models themselves. Today we know that those 2 glycerol esters which Mechoulam’s group identified aren’t the only two compounds able to synergize with endocannabinoids and potentiate their activity. And so the term “Entourage Effect” has been loosely expanded to describe synergistic relationships between various cannabis derived compounds and cannabis' main psychedelic phytocannabinoid, delta-9-THC.
The main psychoactive compound of the cannabis plant is the phytocannabinoid delta-9 tetrahydrocannabinol (THC). For the longest time THC was the focus of the cannabis research community. Meanwhile, the cannabis growers and consumers have been questing to breed cannabis “strains” ( or better cannabis “chemovars”) with increasing concentrations of THC. Consequently, the strains (“chemovars”) that are in circulation today have much higher THC concentrations than what people were consuming decades ago at Woodstock. Beyond this the pharmaceutical industry has produced synthetic THC and high-THC isolates are commonplace now. But THC is not the only cannabinoid, in fact the cannabis plant contains hundreds of cannabinoids and cannabinoid precursors that hold individual bioactive properties in animals and humans and also modulate the activity of THC.
The main psychoactive compound of the cannabis plant is delta-9 tetrahydrocannabinol (THC)
THC is not universally the “best” cannabinoid either. Especially, in a medical context, THC’s psychoactive properties can cause unwanted side-effects. For instance, while pain relief scales well with higher THC content (up to 12.5%) it can under some circumstances cause additional seizures in epilepsy patients which makes it less attractive there. However, significant scientific evidence exists that suggests CBD and other cannabinoids can mitigate some of the unwanted effects of THC. Which also finds application beyond the medical realm.
Some of the most abundant and therefore most researched cannabinoids are:
- delta-9 tetrahydrocannabinol (THC)
- cannabidiol (CBD)
- cannabichromene (CBC)
- cannabigerol (CBG)
- tetrahydrocannabivarin (THCV)
- cannabidivarin (CBDV)
- cannabinol (CBN)
They are all very similar looking molecules that share common precursors and interact with the human endocannabinoid system, nervous system and immune system in various ways via some shared and some alternative pathways. The precursor “acid” versions of the cannabinoids, like for example delta-9-tetrahydrocannabinolic acid also have biological properties, but typically cannabinoids are heated and de-carboxylated before use. While cannabinoids appear to be unique to the cannabis plants, there is another class of compounds present in the cannabis plant that are biologically active, similar to cannabinoids but ubiquitous beyond the cannabis plant. Those compounds are “terpenes & terpenoids”.
Terpenes and Terpenoids are similar to cannabinoids, as they share common precursors. Over 200 variants have been described for the cannabis plant, but overall they constitute the largest group of known plant chemicals with more than 23000 already fully characterized compounds. Terpenes are what give the cannabis plant its flavor and smell. They consist of repeating units of carbon and hydrogen organized in five-carbon “isoprene” blocks. Depending on how many isoprene units are chained together they are classified into:
- Monoterpenes: 2 isoprene units (10 carbon atoms)
- Sesquiterpenes: 3 isoprene units (15 carbon atoms)
- Diterpenes: 4 isoprene units (20 carbon atoms)
- Triterpenes: 6 isoprene units (30 carbon atoms)
- Tetraterpenes: 8 isoprene units (40 carbon atoms)
Terpenes and terpenoids are often conflated with each other when discussed in the media, but they do differ chemically. Terpenes contain only carbon and hydrogen, while terpenoids also contain oxygen atoms as part of alcohol, ketone and aldehyde groups. For the most part terpenes only occur in plants, but some of the longer chained versions have been found in animals as well. Terpenoids are versatile, they interact with cell membrane, ion channels on nerves and muscles, various receptors, such as neurotransmitter and g-protein coupled receptors, secondary messengers and enzymes. In other words, they can interact with a lot of systems in your body. Even so, they are generally considered to be quite safe which is why they are approved by the FDA as food additives. You’ll find them in pretty much any plant we consume. By themselves terpenoids have therapeutic properties. They can be immunostimulant, anxiolytic, anti-inflammatory, analgesic, sedating and even anti microbial. Their volatile lipophilic nature makes them quite bioavailable even when casually breathed in. Which is why they are the basis of aromatherapy.
Aromatherapy cannot replace more directed pharmaceutical intervention
However, it is important to understand that those recorded effects area measurable, but very mild. So aromatherapy cannot replace more directed medically supervised pharmaceutical intervention in case of serious illness. Qualitatively, those beneficial effects have been recorded in the literature, but quantitatively each category has more potent and effective solutions. With regard to cannabis the most common terpenes are monoterpenes and sesquiterpenes. The most abundant ones being:
- Caryophyllene Oxide
Searching for synergy
In 2011 the British Journal of Pharmacology released a special, themed, cannabis issue. As part of this issue they published a review written by cannabis researcher Dr. Ethan Russo who summarized the state of research surrounding the Entourage Effect : “Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects”. It is probably the most cited review on the subject. The review collects cannabinoids and terpenes and tries to identified possible synergistic relationships between them that are summarized in the following two tables:
A word of caution
It is important to understand that the term “Entourage Effect” has since been co-opted and is widely used as a marketing term designed to propagate the idea that the whole cannabis plant is universally better suited to treat illnesses than isolated or synthetic cannabinoids. This is a gross oversimplification from a clinical and scientific point of view and an example of the cannabis industry and media coverage getting ahead of itself. It is possible that in the end we will be able to truly characterize and map out all the active compounds and possible polypharmacological properties of the cannabis plant. And maybe one day we may have the ability to tailor a specific “Entourage Cocktail” to the individual patient.—But we just aren’t there yet. There is evidence of beneficial properties of individual terpenes, but the majority of clinical data discussing the ability of the “Entourage Effect” to potentiate the effects of THC, while also minimizing the adverse side-effects, originates from experiments with THC + CBD, rather than whole plant extracts with varying combinations of terpenoids. Those reports are still mainly anecdotal but have been conflated with the findings on THC and CBD.
The marketing of "The Entourage Effect" is getting ahead of clinical research
Ultimately, what matters is the ability to predict clinical outcomes and we simply don’t have enough strong randomized clinical trial data to attribute universally beneficial properties to the “Entourage Effect”. That doesn’t mean it is not beneficial, it just means it is poorly defined and clinically under-researched. There is certainly reason to be optimistic, the therapeutic properties at least appear to be promising and synergies have also been demonstrated. Even so, we should be wary of overly heavy marketing by entities with significant conflict of interest. The reality is that in many cases we cannot predict the patient outcome with the whole cannabis plant in such a granular fashion as the general marketing machinery will have you believe. Do no harm is still a medical mandate, which is why even with the growing evidence of positive “Entourage Effects” for better or for worse clinicians will mostly stick to synthetic THC like dronabinol.
- Sommano SR, Chittasupho C, Ruksiriwanich W, Jantrawut P. The Cannabis Terpenes. Molecules. 2020 Dec 8;25(24):5792. doi: 10.3390/molecules25245792. PMID: 33302574; PMCID: PMC7763918. https://pubmed.ncbi.nlm.nih.gov/33302574/
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