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One Isomer of HHC Is More Potent Than Another, Study Finds

By Leo Bear-McGuinness

Published: Aug 15, 2023   
Vial of liquid in a gloved hand, next to a cannabis plant.

Image credit: iStock

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THC has had some competition in recent years. Derivatives of the psychoactive compound, such as hexahydrocannabinols (HHCs), are increasingly sought after in many US states, partly due to their more nuanced less status.

But some of these HHC products are inferior to their THC counterparts and others are not. That’s the main finding from a new paper, published in ACS Chemical Biology.

In their study, researchers synthesized two isomers of HHC: (9R)-HHC and (9S)-HHC. They then observed how well the isomers bound to cannabinoid receptors. Both had strong affinities, but (9R)-HHC was stronger and better resembled the actions of THC.

Double isomers

HHC can be synthesized from legally cultivated hemp. Some producers have therefore concluded that HHC products must also be federally legal. However, the US Drug Enforcement Administration (DEA) reportedly considers HHCs as Schedule 1 substances.

Regardless, HHC products are still being sold in states without legal recreational cannabis access, and demand for them is growing.

But demand for which type? For, unbeknownst to many HHC consumers, there are two main varieties of the chemical. The 9R isomer is sometimes referred to as the “methyl equatorial” isomer, whereas the 9S isomer is sometimes referred to as the “methyl axial” isomer.

Both can be produced using catalytic hydrogenation, however this method has low selectivity and the potential to leach heavy metals, contaminating the products.

In their new paper, the researchers from the University of California, Los Angeles, endeavored to outline a new method that could produce specific HHC isomers without contamination. Using hydrogen atom transfer techniques, the produced significant yields of HHCs at a 9.5:1 ration of (9R)-HHC:(9S)-HHC.

The researchers then performed several cell assays to determine how well the two HHC isomers bound to CB1 and CB2 receptors. (9R)-HHC bound to both receptors better than (9S)-HHC. The former’s affinity for the cannabinoid receptors was practically as strong as THC’s.

“These studies are crucial if we are to have laws and policies that are fair and allow for consumer safety, while allowing scientists and society alike to explore the potential therapeutical effects of new cannabinoids,” Neil Garg, a professor of chemistry at the University of California, Los Angeles, and co-author of the paper, said in a statement.

The study was funded by ElectraTect Inc., a startup company spun out of Garg’s research, and performed with an appropriate DEA license.


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