Posted by Skunk Pharm Research,LLC.
Introduction to a cold extraction method for hash oil that preserves carboxylic acid form of cannabinoids THC and CBD
By Kate Welch, Pharm.D
The cannabinoids THCA and CBDA, short for delta-9 tetrahydrocannabinolic acid and cannabidiolic acid, respectively, are precursors to their more well-known and well-studied metabolites, THC (aka delta-9 tetrahydrocannabinol), the primary psychotropic cannabinoid found in cannabis, and CBD (cannabidiol), its primary non-psychotropic cannabinoid.
Found most abundantly in fresh cannabis plant material (Eichler et al. 2012; Turner et al. 1980), THCA and CBDA de-carboxylate the acidic part of the molecule into the active molecules THC and CBD. This occurs primarily by exposure to heat via smoking, cooking, or heated extraction of the dried or fresh plant, but also can form more slowly over time via extended exposure to light and atmosphere (Hazekamp 2008).
Until recently, THCA and CBDA were not considered to be able to survive metabolism (i.e. inhalation by the lungs or digestion by the stomach and intestines and processing by the liver); nor were they considered to have any pharmacological activity in and of themselves (Jung et al 2007; Takeda et al 2008).
However, recent in vitro and animal research using extracted THCA or CBDA reveals measurable actions on certain enzymes and receptor sites, suggesting some potential therapeutic effects for these cannabinoids and necessitating the elucidation and refinement of specific extraction techniques that preserve these particular acidic forms of these cannabinoids in order to provide material for further experimentation and research.
CBDA was the earliest discovered cannabinoid acid, in 1955 (Brenneisen 2002). As for THCA, there are actually two forms: THCA-A was isolated in 1965; THCA-B, an analogue, was isolated in 1975. Some plants express more of one or the other for unknown reasons (ElSohly and Gul 2014), but THCA-A is usually the most prominent, and the most studied (Brenneisen 2002). For the purposes 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 decarb