The pharmacological effects of most cannabinoids remain a mystery. Despite more than 120 identified cannabinoids in the cannabis plant, very few other than THC (tetrahydrocannabinol) and CBD (cannabidiol) have been isolated and characterized in terms of their pharmacological properties. The newest identified cannabinoid is THCP (tetrahydrocannabiphorol) and is many times more potent than THC.

THC is recognized as the primary intoxicating cannabinoid found in the cannabis plant. Studies have shown that the strength of THC’s intoxicating effect is influenced by the length of the side alkyl chain on the molecule. Naturally occurring THC has a five-carbon side chain. Synthetic analogues of THC with a longer side chain bind more tightly to the human cannabinoid receptor CB₁and have resulted in intoxicating potency many times higher than naturally occurring THC. A minimum of three carbons is necessary to bind the CB₁receptor, and the highest binding activity has been registered with an eight-carbon side chain.

Discovery of THCP

No cannabinoid with a side chain containing more than five carbon atoms has ever been reported as naturally occurring. In a paper published in the journal Scientific Reports on December 30, 2019, however, Italian researchers confirmed the discovery of a naturally occurring cannabinoid with the same structure as THC but with a seven-carbon side chain. This new cannabinoid has been named tetrahydrocannabiphorol, or THCP. It was isolated from a medicinal cannabis variety, the Italian FM2.

THCP May Be 30 Times More Potent than THC

It is expected that THCP will prove to have a high binding affinity for the CB₁receptor and a greater intoxicating effect than THC. Initial test results indicate that THCP may have a binding affinity for the CB₁receptor more than 30 times higher than THC.

Does THCP Explain Why Cannabis Strains with Similar THC Levels Cause Varied Effects?

The Italian researchers theorize that the presence of THCP could account for the pharmacological properties of some cannabis varieties that are difficult to explain by the presence of THC alone. Though the cannabis variety used for the study has a very low concentration of THCP, other cannabis varieties may contain higher concentrations. The authors point out that “there exists an astonishing variability of subject response to a cannabis-based therapy even with an equal THC dose.” They conclude that this may be due to the effect of extremely active cannabinoids such as THCP, but note that inadequate research has been conducted to date.

Given the potency of THCP, the paper concludes by recommending that THCP be included in the list of the main cannabinoids, along with THC and CBD, when evaluating the pharmacological effects of cannabis varieties.

Will New Product Labels and Warnings Be Needed?

The findings on THCP inevitably raise the questions of whether there are other highly potent cannabinoids that have not yet been identified and whether product label changes will be needed. As cannabinoid science progresses and new compounds are identified, it is likely that product labeling and consumer warnings will become more complex. Most labels on cannabis products currently focus on THC and CBD concentration to the exclusion of other potentially potent cannabinoids. This label practice may need to evolve with the science, and this evolution may start with THCP.