Analyzing THC Concentrates? Look for Isomers!

As we learn more about the chemical constituents of cannabis, more cannabinoids are being discovered and with it more THC isomers. You are probably very familiar with the two most commonly tested: Delta-9-THC and Delta-8-THC. There have been a total of 30 different isomeric forms of THC discovered thus far including different conformations. These isomers all share the molecular formula C₂₁H₃₀O₂. In this blog, we will be focusing on isomers of THC that vary by the location of the double bond located on the methylcyclohexene ring.

Delta-9-Tetrahydrocannabinol

Also known as: THC, dronabinol

Delta-9-THC is the main psychoactive component found in cannabis. This compound has a double bond on carbons number 9 and 10 and was listed as a Schedule I drug by the UN Convention of Psychotropic Substances in 1971 and remains federally listed in the US as Schedule I substance today. In the United States, when the 2018 Federal Farm Bill was passed, hemp products were allowed to be sold as long as they do not contain more than 0.3% of delta-9-THC. In the body, two metabolites are formed from delta-9-THC; 11-hydroxy-THC and THC-COOH.

Delta-8-Tetrahydrocannabinol

Delta-8-THC is an analogue of Delta-9-THC and only differs by the placement of the double bond on carbons number 8 and 9. It is also psychoactive but is potentially less potent. The passing of the 2018 Farm Bill in the United States initially did not include language for delta-8-THC, allowing this compound to fly under the radar, but has since become illegal to convert CBD into delta-8-THC in several states. Delta-8-THC produces hydroxylated and carboxylated forms of delta-8-THC in the body, similar to the delta-9-THC metabolites.

Exo-Tetrahydrocannabinol

Also known as: Delta-9,11-THC

Exo-THC differs from the other two isomers by the double bond location on the methyl group located on carbon 9. This compound is not typically found naturally in cannabis and could potentially be an indication of synthetic THC or formed during an extraction/sample preparation procedure.¹ Its metabolites are similar to delta-8 and delta-9 forming hydroxylated and carboxylated compounds but with the location on the double bond on the methyl group of carbon 9.

Delta-10-Tetrahydrocannabinol

Delta-10-THC has the location of the double bond between carbons 10 and 10a. It is thought to not have psychoactive effects but testing is somewhat limited and could have diluted psychoactive effects.

As I mentioned before there are many more isomers but for this blog we’re going to stick with these four because of current interest. It’s important to be able to separate these isomers if you need to perform a potency test on concentrates to obtain accurate quantitation for each compound. These THC isomers all have their own benefits and as more are being discovered, there is more interest for potency testing labs to be able to detect them.

Here, a method has been developed to baseline separate four THC isomers, exo-, delta-8-, delta-9-, and delta-10-THC in 4 minutes using an isocratic method. By implementing an isocratic method you can cut down on overall run time by eliminating the equilibration step between runs.

By using this method to look at THC concentrates, your lab can cut back on instrument time due to the rapid analysis and save money by using methanol as opposed to acetonitrile. This method also allows for baseline separation of all four isomers allowing for accurate identification and quantitation.

While we are discussing new cannabinoids of interest, I want to direct your attention to two recently discovered cannabinoids that have recently been added to our cannabinoid assays, tetrahydrocannabiphorol (THCP) and cannabidiphorol (CBDP).² 

Interested in a certain topic and want it covered in the next blog? Send us an email with your cannabis laboratory/workflow questions and topics and it could be our next blog post!

References:

1. Society of Cannabis Clinicians July 27^th, 2020. “What is exo-THC?” https://www.cannabisclinicians.org/2020/07/27/what-is-exo-thc/
2. Linciano, P., et al. Journal of Natural Products, 2020, 83 (1), 88-98.