For years, it was thought that cannabis was the only plant capable of producing cannabinoids. However, in the last few years research has been published that shows that cannabis is not the only plant that produces these compounds, and that they are actually quite common!
Cannabinoids are lipid-based molecules that all act to some degree on the cannabinoid receptors, which are a primary component of the endocannabinoid system. Cannabinoids are produced by plants (most famously, the cannabis plant), but are also produced by the bodies of humans and most other animal species, and can also be synthesized in laboratories.
Cannabinoids produced by plants are known as phytocannabinoids, those produced by the body are known as endocannabinoids, and lab-synthesized compounds are simply known as synthetic cannabinoids.
Most cannabis enthusiasts will have heard of the classic cannabinoids such as THC, CBD, THCV and CBC, which for many years were thought to be the only compounds that acted on the cannabinoid receptors. The classic cannabinoids all share the same chemical formula, C21H30O2.
However, as our understanding of the endocannabinoid system has grown, we have found that the number and type of different compounds that act on the receptors is far larger.
Thus, we have to widen the goalposts somewhat as to what constitutes a cannabinoid—beyond the 120 or so classic cannabinoids, there are also an as-yet-undetermined number of related compounds, which also act on the receptors but do not share the classic structure.
As well as cannabinoids, we also have an important class of non-classical cannabinoids known as cannabimimetics. They are called cannabimimetics as they literally mimic the biological activity of the classical cannabinoids, despite not sharing their structure.
Cannabimimetics are of increasing importance within the world of medicinal cannabinoid research. Classically, the EC system has been viewed as a simple set of two receptors and two ligands (a ligand is the term for a compound that binds to a receptor).
However, it is now increasingly being shown that the EC system is far more complex than this. Dozens of different compounds are now known to act either directly or indirectly on the EC system, and many of these compounds also work on other important biological messaging systems such as the opioid, serotonergic and dopaminergic signalling systems.
N-acylethanolamines are a class of fatty acid compounds which are known to be heavily involved in biological signaling. NAE’s include N-arachidonoylethanolamine (better known as anandamide), N-palmitoylethanolamine (PEA), N-linoleoylethanolamide (LEA), and N-oleoylethanolamine (OEA).
Anandamide is well known for being the biological compound which most closely resembles the activity of THC, as it directly agonizes the principal cannabinoid receptors. It is now also known that anandamide also directly agonizes a third cannabinoid receptor known as GPR119, which is also affected by N-oleoylethanolamine.
As well as directly acting on the principal and minor cannabinoid receptors, NAE’s are also known to exert a range of indirect effects. For example, LEA, PEA and OEA all inhibit levels of the FAAH enzyme that is responsible for degrading anandamide itself, and thus can effectively increase levels of anandamide in tissues over time.
N-alkylamides are a similar but less well-researched class of cannabimimetic compounds that have been shown to exert selective effects on the CB₂-receptors, and have been shown to exert anti-inflammatory effects similar to anandamide.
This important terpene is found in cannabis, and its oxide (which forms on contact with air) is the compound detected by drug-sniffing dogs! B-caryophyllene has been shown to act as a full agonist of the CB₂-receptor, although it does not act on the CB₁-receptor.
It has also been shown to exert anti-inflammatory and analgesic effects in mice, but not in mice bred to lack CB₂-receptors—showing that this biological activity is exerted via the receptors themselves.
Salvinorin A is the main component of the psychoactive plant species Salvia divinorum. Unusually for a hallucinogenic plant compound, salvinorin A is a terpenoid, not an alkaloid like mescaline, psilocybin and DMT. Furthermore, it is a dissociative, rather than a classic hallucinogen.
Interestingly, it seems that salvinorin A does not interact with the classic cannabinoid receptors, but in fact interacts with a putative third cannabinoid receptor that apparently forms only in inflammatory conditions, and which also acts as a kappa-opioid receptor. The κ-opioid receptors are fundamental to pain regulation, and are also the principal target of most hallucinatory compounds!
Another very important terpene found in cannabis, and one that is also a major constituent of the essential oil of hops. Although it is not thought that myrcene directly acts on the cannabinoid receptors, it is now known that its biological activity alters the psychoactive effect of THC.
Myrcene is known to be present in high levels in strains that exert a ‘stoney’ or ‘couchlock’ effect on the user. The sedative effects of myrcene-containing plants such as hops and verbena have been known for millennia, and it is now thought that the sedative effect is due to myrcene’s ability to agonise (activate) the opioid receptors (studies have shown that the opioid antagonist naxalone blocks myrcene’s effects, suggesting that myrcene is an agonist).
Thus, although myrcene isn’t typically classed as a cannabinoid in the currently existing scientific literature, it certainly affects the subjective experience of the cannabis ‘high’. Further research will no doubt determine the exact nature of the link; presently, while testing labs such as Steep Hill Halent in California have been collecting data on the association for years, no formal studies have as yet been conducted.
First off, there are abundant plant sources of terpenes such as β-caryophyllene and myrcene, although of course, some sources are better than others. Myrcene is found in extremely high concentrations in hop oil, making up almost 80% of the extracted volume in some varieties, and is also found in high levels in mangoes, lemongrass, thyme, and verbena.
B-caryophyllene is found in black pepper, cloves, rosemary, hops, caraway, oregano, basil, lavender, cinnamon, and many more plant species. In most of these species, β-caryophyllene is a major constituent of the essential oil (comprising 20% in some hop species).
Salvinorin A is much rarer, and appears to only be found in high quantities in S. divinorum itself. However, there are indications that other sage species may also contain traces of the compound itself, or closely related molecules.
NAE’s including OAE, PEA and LEA have been found to occur in many plant species. Notably, OAE and LEA have both been found in the cocoa plant, and black truffles have even been reported to contain anandamide itself! Lastly, the compounds known as N-alkylamides have been found in various echinacea species, and it is thought that echinacea’s importance in herbal medicine may derive from this fact.
In time, the list of plants that can safely be said to contain cannabimimetic compounds will no doubt expand dramatically, as we continue to find compounds capable of acting on the EC system.
Up until very recently indeed, it seemed that the cannabis plant was unique in producing the true, classic cannabinoids. However, this conventional wisdom appears to have been turned on its head with the discovery in 2012 that flax (linen) seeds produce cannabidiol (CBD)! Or at least, that they produce cannabinoid-like compounds very similar to CBD, which appear to have similar anti-inflammatory effects.
However, there is in fact a much earlier piece of research suggesting that the compound cannabigerol (CBG) and its precursor cannabigerolic acid (CBGA) are present in a South African herb, and a more recent (2011) study suggesting that cannabichromene (CBC) and some related compounds are present in Chinese rhododendron.
Lastly, there is even a plant known as the New Zealand liverwort, which produces an unusual type of cannabinoid (called perrottetinenic acid) that appears to be very closely related to THC, so much so that it may actually act on the CB₁-receptor! If this is the case, it will be the only other known plant compound found in nature that is capable of doing so. However, whether or not this compound actually acts on the CB₁-receptor is not yet known.
And one thing we seem to know for sure: no other plant aside from cannabis produces THC.
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