urposes of this article, THCA= THCA-A as found in the fresh or dried cannabis plant.
First, it is important to distinguish between the carboxylic acids that are precursors to THC and CBD in the fresh or dried plant material, and those that are the acid metabolites of smoked or ingested THC and CBD, formed in the liver or tissues and found in the bloodstream and filtered through the urine for excretion.
The primary non-psychoactive metabolite of THC is also an acid, 11-nor-9-carboxy-delta-9-tetrahydrocannabinol (Foltz 2007). This metabolite forms via the enzyme alcohol dehydrogenase from the primary liver-produced metabolite of THC, the equally psychoactive 11-hydroxy-THC.
Removal of pure THC occurs rapidly from the bloodstream; 11-nor-9-carboxy-delta-9-THC accumulates and continues to form and be excreted into the urine as the THC in the bloodstream or from tissues that secrete stored THC into the bloodstream. As a result, urine drug assays intended for detection of human cannabis consumption primarily screen for the presence of this particular form of THCA (Chesher and Longo 2002).
Animal research confirms that biological enzymes do not themselves convert THCA to THC: pure THCA given to rats led to acid metabolites of THCA only, not THC or acid metabolites of THC (Jung 2007).
THCA and CBDA lack psychoactive effects (Kwong 2002) even when administered in pure form by IV to animals or humans (Grunfeld et al 1969). There is no evidence at this time that the acidic metabolites produced in vivo share the potential biological effects of it acidic precursors present in the fresh or dried plant.
Quantitative detection of THCA in raw plant material heretofore has primarily been intended to help predict the THC potency of a specific weight or volume of dried plant when it is eventually smoked or heated; liquid chromatography (HPLC) is preferred since it is important that the method of detection must not heat the sample which will immediately convert THCA to THC (Ambach et al 2014).
Furthermore, lab analysis of this decarboxylation reaction provides estimates that smoking cannabis yields approximately a 30% conversion of THCA to active THC; other methods such as cooking or heated solvent extractions will yield 70-90% conversion (Dussy et al 2005).
However, it is important to note that to date there is poor correlation between the percentage of THCA to THC conversion already present in a cannabis product to be consumed and the resulting pharmacokinetics (measurements in the bloodstream) or pharmacodynamics (measurable psychoactive or psychomotor effects) in humans. For example, a small study compared the levels of THC and THC metabolites (both active and inactive) in men who consumed a fixed amount of either a) a heated cannabis sativa extract; b) and unheated cannabis sativa extract; or c) pure pharmaceutical THC (aka dronabinol or Marinol®).
The unheated extract, surprisingly, turned out to provide both the highest CBD and THC blood levels on average, suggesting that whatever CBD and THC was initially ingested from the cold extract was readily absorbed and persisted in the bloodstream the longest. The heated extract, however, provided the highest total exposure to THC activity because of the sum of THC plus active metabolite 11-hydroxy-THC measured in the bloodstream. Both extracts measured blood levels of THC on average higher than in subjects given the pure pharmaceutical THC, even though both the unheated and heated cannabis extracts were CBDA dominant strain (CBDA/THCA ratio >1) (Eichler et al 2012).
While the above study provided some interesting evidence about the fate of CBD and THC after oral consumption from either heated or unheated extracts, it did not examine the pharmacokinetics or pharmacodynamics of CBDA or THCA, though there were more of these acidic forms of the cannabinoids present and ingested in the unheated extract than the heated one (and none present in the dronabinol). Thus, important questions remain about both the unique biological effects of these acidic cannabinoids on the human body as well as their p