Cannabis has long been recognized as the sole natural source of Delta-9-tetrahydrocannabinol (THC), the compound responsible for its psychoactive effects. THC belongs to a class of molecules called cannabinoids, which are produced within specialized glandular structures on the plant’s surface. A compelling scientific question is whether other plants produce genuine THC or molecules with similar biological activity. The answer requires distinguishing between true THC production and the broader phenomenon of plants producing compounds that interact with the human endocannabinoid system.
The Biochemical Rarity of THC Production
The production of genuine THC is an extremely rare biochemical event in nature, essentially exclusive to the Cannabis genus. THC does not spontaneously form in the plant; it originates from a precursor molecule called cannabigerolic acid (CBGA). The conversion of CBGA into the non-psychoactive tetrahydrocannabinolic acid (THCA) requires a highly specific enzyme called THCA synthase.
This enzyme, THCA synthase, is the defining component of the THC biosynthetic pathway. It catalyzes an oxidative cyclization reaction on CBGA, forming the characteristic tricyclic structure of THCA. The gene for this enzyme is only expressed in the glandular trichomes of Cannabis sativa.
Finding this specific enzymatic machinery in an unrelated plant species would be a discovery of parallel evolution. While some plants can create CBGA, the precursor, they lack the unique synthase enzyme needed to perform the final step of converting it into THCA. This genetic specialization makes the search for true THC in other botanicals largely unproductive.
Plants That Interact with the Endocannabinoid System
While other plants do not produce THC, many contain structurally distinct compounds that are biologically active on the human body’s endocannabinoid system (ECS). These compounds are often referred to as “cannabimimetics” because they mimic the activity of cannabinoids. They represent a different evolutionary approach to influencing the same physiological pathways that THC affects.
The North American perennial herb Echinacea, commonly known as the purple coneflower, is a prime example. This plant contains a class of fatty acid derivatives called N-alkylamides (AKAs). These AKAs are known to bind to and activate the cannabinoid type 2 (CB2) receptor, which is predominantly involved in regulating immune function and inflammation.
The activation of the CB2 receptor by Echinacea N-alkylamides is one mechanism by which the plant is thought to exert its anti-inflammatory and immunomodulatory effects. Unlike THC, which acts primarily on the CB1 receptor, the AKAs show a preference for the CB2 receptor. These N-alkylamides can also modulate the ECS by affecting the transport and breakdown of the body’s own endocannabinoids.
Another example is the South African shrub Helichrysum umbraculigerum. Research indicates that this plant produces cannabigerolic acid (CBGA), the same precursor molecule found in Cannabis. However, it does not convert CBGA into THC or CBD; instead, it creates Heli-CBG, a phenethyl analogue of CBG. This suggests parallel evolution where two distinct species developed similar biosynthetic capabilities but utilize them differently.
The Botanical Confusion: Hops and Related Species
The common hop plant, Humulus lupulus, is frequently mentioned in discussions about non-cannabis sources of THC, largely due to its close botanical relationship. Both Cannabis and Humulus belong to the same plant family, Cannabaceae, but they diverged evolutionarily over 20 million years ago. Despite this shared ancestry, hops do not produce THC or any of the classical cannabinoids.
The confusion stems partly from the presence of aromatic compounds, known as terpenes, which are common to both plants. Hops contain significant amounts of terpenes like myrcene and humulene, which contribute to the flavor and aroma of beer. Humulene is a sesquiterpene also found in Cannabis and has been researched for its potential to interact with the endocannabinoid system, though not as a direct cannabinoid.
Hops lack the specific enzymes, such as THCA synthase, that would allow them to convert precursor molecules into actual cannabinoids. While terpenes in hops may contribute to mild sedative effects or interact indirectly with the ECS, they are fundamentally different in chemical structure and biological action from THC. The presence of these shared aromatic molecules and the family connection is the primary source of the inaccurate idea that hops contain THC.