All cannabinoids in cannabis begin their life as either CBGA or CBGVA. These cannabinoids then get transformed into the many familiar cannabinoids through various processes involving plant enzymes, decarboxylation from heat, and degradation from light, temperature, and acidic enzymes.
Cannabis plants are known to contain enzymes that are responsible for catalyzing the formation of specific carboxylic acid forms of cannabinoids. Genetic various in each strain are responsible for the amount of THCA synthase, CBDA synthase, CBCA synthase, etc. that play a role in the plants overall cannabinoid potency. For example, a primary difference between hemp and marijuana is the overabundance of THCA synthase enzymes produced by the cannabis plant.
With the assistance of THCA synthase, the following reaction occurs:
CBGA + O2 ⇌ THCA + H2O2
Decarboxylation occurs when heat is applied to drive off the carboxylic acid function group in the form of carbon dioxide (CO2) leaving the parent molecule. The carboxylic acid forms of cannabinoids are fairly fragile and decarboxylation can occur slowly at room temperature or the process can be intentionally sped up in an oven. Stability data on analytical standards for these cannabinoids has shown they degrade or decarboxylate at a rate of around 2-6% every 4 weeks at room temperature. Conversely, decarboxylation can occur to reasonable completion after 60 minutes in a 245°F oven. However, too much heat has the potential to degrade cannabinoids further. A typical chemical equation of this process is represented below:
In addition to too much heat, other degradation products can result from exposure to too much light or oxidation as they age. The most commonly used example is the degradation of THC to CBN, where the ratio of CBN to THC can be used to obtain a rough estimate of a cannabis sample. Refer to this article regarding the stability of cannabinoids for more info.
Transformation of Cannabinoids from CBGA and CBDVA
As previously mentioned, CBGA and CBDVA are the precursors to all other cannabinoids. We first need to examine how these two cannabinoids are produced by the plant before we can examine the biosynthetic pathway of other known cannabinoids.
CBGA is formed with geranyl pyrophosphate and olivetolic acid in the presence of the enzyme geranylpyrophosphate:olivetolate geranyltransferase (GOT) (1,2). CBGVA is formed with geranyl pyrophosphate and divarinic acid in the presence of a different transferase enzyme (2).
- CBGA can utilize enzymes in the cannabis plant to produce THCA, CBDA, and CBCA (3)
- CBGA can decarboxylate into CBG.
- THCA can decarboxylate into delta-9 THC or degrade into CNBA (3).
- Delta-9 THC can degrade into delta-8 THC. (4)
- Delta-9 THC can degrade into CBN. (5)
- CBNA can decarboxylate into CBN.
- CBDA can decarboxylate into CBD. CBDA can also undergo photo-oxidation into CBEA (6,7), which can then decarboxylate into CBE.
- CBD can undergo photo-oxidation CBE. (7)
- CBCA can decarboxylate into CBC. CBCA can also undergo photo-oxidation into CBLA (7), which then can be decarboxylated into CBL.
- CBGVA can utilize enzymes in the plant to produce CBTV, CBCVA, CBDVA, and THCVA
- CBGVA can also be decarboxylated with heat resulting in CBGV.
- CBCVA can be decarboxylated to form CBCV and CBCVA can also degrade to CBLVA.
- CBLVA can be decarboxylated to form CBLV.
- CBDVA can be decarboxylated to form CBDV. CBDV can then degrade into CBEV as well as CBNDV.
- THCVA can be decarboxylated to form THCV. THCV can dergrade into CBV.
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