The Facts on “Delta-8” THC and Other Isomers of THC

POSTED April 19, 2021

Dr. Meghan McCormick talks safety, legality, and why you should care about Delta-8 THC.

Is ‘delta-8’ legal?

Delta-8 THC, or Δ8-THC, is a shorthand name for Δ8-tetrahydrocannabinol, and it refers to an analogue of the famous delta-9 THC, which the DEA has classified as a Schedule 1 drug and therefore federally illegal. Technically, delta-8 THC is considered federally legal if it is derived naturally from hemp in states with a hemp program:

“In December of 2018, the 2018 Farm Bill was signed into law. It removed hemp, defined as cannabis (Cannabis sativa L.) and derivatives of cannabis with extremely low concentrations of the psychoactive compound delta-9-tetrahydrocannabinol (THC) (no more than 0.3 percent THC on a dry weight basis), from the definition of marijuana in the Controlled Substances Act (CSA).”

Unfortunately, delta-8 is naturally found in hemp and cannabis in inconveniently small amounts (<1%), and as a result, some people have resorted to synthesizing it from relatively inexpensive CBD or through other complex synthetic pathways to use in their products. Since this synthetic conversion is not a natural plant process legal issues are now raised as well as any safety issues from synthetic production that have not been researched thoroughly (this will be covered more below). In its interim final rule published on August  21, 2020, the DEA said “All synthetically derived tetrahydrocannabinol remain a schedule I controlled substances.”

Lastly, drug tests cannot differentiate between delta-8 and delta-9 THC due to the similarity in the metabolites measured during urinalysis tests, so that is always something to keep in mind when consuming or selling delta-8 THC products.

Why should I care about ‘delta-8’ THC?

The increased interest in delta-8 THC comes from three simple points: similar effects to Δ9-THC, potential medicinal benefits, and it’s technically legal on a federal level.

There are, however, some caveats to go with the above statement. Delta-8 THC exhibits similar but “lower psychotropic potency” than delta-9 as it might bind with the brain’s receptors differently than delta-9. Limited amounts of research have been completed on delta-8 THC; as a result, how it interacts with the body’s receptors, how it can be used for specific treatments, and how it affects people long term is still undetermined. Finally, delta-8 THC is only federally legal through hemp extraction and extensive post-processing steps, which is not always the most lucrative.

What does the “delta” stand for?

Writing out the full IUPAC chemical name for delta-8 or delta-9 THC is a mouthful and not exactly helpful for understanding the current popular synonym. Not to mention, the use of ‘delta’ in a chemical’s name is outdated for today’s chemical nomenclature rules and currently only applies to cannabinoids to distinguish between various isomers.

When referring to an isomer, it is with another chemical or molecular structure in mind. To clarify, an isomer is a chemical compound with same number of atoms as another chemical compound, but with a different arrangement of those atoms via their chemical bonds. In the case of isomers delta-8 and delta-9 THC, the difference appears in the location of the double bond in each molecule’s top ring, seen in the structures drawn in Figure 1. In delta-9 THC, the double bond occurs between C9 and C10, whereas in delta-8 THC, the double bond is found between C8 and C9.

Since there is no biosynthetic pathway for the formation of delta-8 THC in the plant, it is instead surmised to be a degradation product of delta-9 THC, similar to other cannabinoids like CBN. This specific degradation process is called isomerization and is most likely triggered by heat or UV light in the presence of an acid. Consequently, trying to genetically modify a cannabis plant to produce more delta-8 THC is essentially not possible without creating a direct biosynthetic pathway.

Figure 1: molecular structures of ‘delta-8 THC’ and delta-9 THC’ and their modern-day numbering system for each carbon atom

Are ‘delta-8’ products safe?

The short answer is that the scientific community doesn’t know… yet. Most products that contain delta-8 THC are a result of a synthesized version, which mostly likely contain a lot of unknown components. Given these ‘unknowns’ there is no way to make any claims about the safety of a product.

The reason behind this lack of knowledge is the presence of so many THC isomers (Table 1). Structural isomers exist when the number and type of atoms are the same, but they are just bonded differently, like Δ8-THC and Δ9-THC (Figure 1). These isomers are similar to rearranging a sectional sofa: all the same pieces are there, but they are connected differently.

Table 1

What most people in the cannabis industry don’t realize is that in addition to the seven structural isomers of THC (Δ8-THC, Δ9-THC, Δ10-THC, etc.) there are many more stereoisomers, which changes how atoms are spatially oriented. As a result, there are a whopping 30 total isomers of THC! It may come as a surprise, therefore, that the cannabis plant consistently and naturally synthesizes only one isomer: (6aR,10aR)-Δ9-THC, which is the one regulated by the DEA. The delta-8 THC isomer naturally found in cannabis plants is the analogous stereoisomer of delta-9 THC previously mentioned (Figure 2, top left).

Figure 2: the four stereoisomers of ‘delta-8 THC’; the top left isomer is the one naturally found in cannabis plants in small amounts

Unfortunately, when delta-8 THC is produced synthetically, there is usually little control over which stereoisomers or side-products are produced, as is the case with most fast and easy organic synthesis methods. One isomer out of many might react poorly in the body until it is further examined via efficacy and toxicity studies. This hasn’t been a big problem so far with natural oil extracts due to low or non-existent amounts of rare THC isomers. In addition to unknown products, reagents used during synthesis might still be present and difficult to remove completely.

Some form of chromatography may immediately come to mind as the solution to these impurity problems. Chromatography could offer solutions for removing side-products and excess reagents; however, separating stereo- and structural isomers requires a lot more work. Isolating individual isomers via chromatography requires special (and expensive) chiral columns additionally to the method development work from small scale to large scale.

In short, sometimes a simplified name (or commonly promoted product in this case) is hiding a world of complexity and unknowns. Just because it is not illegal to sell it, doesn’t mean it has been tested as safe for consumption.

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