THC VS THCa

Last updated on 22 November 2021

Introduction

THC and THCa originate from the same mother compound CBG but exhibit different properties.

THC or Tetrahydrocannabinol is one of the naturally occurring cannabinoids purified from cannabis plants. And, Tetrahydrocannabinolic acid (THCa) is the acidic precursor of THC. 

Since the invention of THC in 1964, it has occupied central focus because of its therapeutic value and psychoactive properties. Misuse of the compound by some sections has left it inaccessible to seekers who might get benefitted from its medicinal properties. 

Therefore, better knowledge and improved awareness could go a long way in bringing about a structure to the growing Industry.

This article aims to present the key differences between THC and THCa based on scientific evidence while also understanding the benefits of each of these compounds.

THC Vs THCA- A quick overview

Property	THC	THCa
Cannabinoid	Naturally occurring	Naturally occurring
Bio-synthesis	THCa decarboxylase to THC	THCa is a precursor to THC. It is the acid controlling the psychoactivity of cannabis sativa
Psychoactivity	Psychoactive	Non-psychoactive
Benefits	Therapeutic applications & recreational	Therapeutic applications
Availability	THCa has to be decarbed to derive THC	Can be found in freshly harvested plant
Molecular structure	C21H30O2	C22H30O4
Interaction with ECS	Exhibits high affinities and physiological activities.	Exhibit poor potency at CB receptors

The above table gives a quick glimpse to understand the difference between THC and THCa. There is more to know from scientific references.

Background of THC

To begin with, some references from literature, a 2006 study¹ provides a reference that THC was first extracted by Wollner, Matchett, Levine, and Loewe in the year 1942 as a mixture of -Δ8 and Δ-9 THC. Later, in 1964, its isolated form Δ9THC from cannabis was derived and synthesized in Raphael Mechoulam’s laboratory. And their chemical structures were also decoded. 

Tetrahydrocannabinol or Δ9 THC is the primary psychoactive component in the cannabis plant known for its neurological and psychological effects. 

Even before we get into discussing the morphology of THC, a brief overview of its chemotypes could help simplify our understanding of THC. 

• According to a 2011 study² THC is the most common phytocannabinoid that is produced in the Cannabis drug chemotypes.

• While there have been different approaches to classifying the chemotypes of cannabis, analysis from a 2016 study³ reports that in 1971, cannabis was first characterized into two phenotypes. The third category was identified in 1973.

1. THC:CBD ratio > 1, it was a drug type, 
2. THC:CBD <1 it was a fiber Type 
3. THC: CBD close to 1 – Intermediate type. 

• Followed by the 2018 study⁴ provides yet another insight. The below table provides a summary of the same.

Chemotype	Characteristics	Usage
I	drug type plants with a predominance of Δ9-THC-type cannabinoids	-Medicinal or recreational purposes, -Most investigated
II	plants with intermediate characteristics between drug-type and fiber-type plants	-Textile or food purposes
III & IV	fiber-type plants containing high levels of non-psychoactive cannabinoids and very low amounts of psychoactive ones	-Textile or food purposes- Contain cannabinoid acids, cannabidiolic acid (CBDA), cannabigerolic acid (CBGa), followed by their decarboxylated forms: cannabidiol (CBD) and cannabigerol (CBG)
V	fiber-type plants  containing almost no cannabinoids	-European countries have approved for commercial use. -The Commercial value of hemp and a legal limit of 0.2-0.3% THC is usually applied.

A 2012 study⁵ points out as ‘direct defenses’ that are characteristic of the plant biology that acts as mechanical protection on the surface. 

For example, hairs, trichomes, thorns, spines, or thick leaves. Even more terpenoids, alkaloids, phenols that either kill or retard insects, or animals.

Furthermore, inferences from the 2012 study⁶ clarifies that these trichomes contain abundant cannabinoids. The capitate stalked trichomes (large), contain tetrahydrocannabinol acid ( THCA), cannabidiolic acid ( CBDA), cannabigerolic acid ( CBGA) including their decarboxylated derivatives Tetrahydrocannabinol, THC, cannabidiol CBD, and cannabigerol CBG.

Role of THC in the Endocannabinoid system

The endocannabinoids and their receptors are present throughout the body and are involved in the complex actions of all organs. Including, the immune system and nervous system.

Even more, the 2013 study⁷ asserts that the endocannabinoids are the major physiological activators of CB1 and CB2, yet they are not standard neurotransmitters.

From the 2017 study⁸ we can understand that the CB1 receptor is the predominant form with abundant G -protein-coupled receptors found in the brain, central nervous system, liver, kidneys. 

More importantly, it is this CB1 receptor that binds the main psychoactive ingredient in marijuana that is THC and mimics its effects. 

On the other hand, CB2 receptors work more independently and are found in the cells and tissues of the immune system. They exhibit a more defined pattern in the brain. 

In a nutshell, according to the 2013 study⁷ THC, acts on the brain by muscling in on the neuronal signaling system ( the receptors) by mimicking it and hijacking it. 

Medical Benefits of THC

• 2011 study⁹ reports THC’s analgesic, muscle relaxant, and antispasmodic properties. In addition, it is a bronchodilator, neuroprotective antioxidant, and has 20 times the anti-inflammatory power of aspirin. 

• In a 2019 study¹⁰ THC has been reported to have generated measurable improvements in symptom relief. As well as this study emphasis that Cannabis with THC could be more widely accessible for pharmaceutical use.

• The 2014 survey study¹¹ conducted among 100 patients who used cannabis for one year, reported on some of the therapeutic benefits. They are relief from stress, anxiety, insomnia, improved appetite, relief from depression, and discontinuity from medications for pain.

THC: Overuse or effects

Besides the growing body of knowledge with regard to the scope of therapeutic applications of medical marijuana, it is always good to equally understand the implications of overuse or misuse. 

The 2014 study¹² points out risks of addiction. Especially, marijuana use by adolescents, in particular, is troublesome. Besides this, Impaired neural connectivity in specific brain regions, Increased risk of anxiety and depression, psychoses for people with pre-existing history are some of the risks attributed to marijuana use. 

More importantly, with respect to the risks of motor vehicle accidents, overuse of marijuana poses adverse effects. 

On this subject the 2020 study¹³ reports that THC causes psychomotor impairment and puts the driver at increased risk of motor vehicle collisions. Regular cannabis users tend to show persistent elevation of THC even after a period of abstinence. 

A 2009 study¹⁴ illustrates that THCA is the acidic precursor of THC by non-enzymatic decarboxylation. Additionally, THCa is biosynthesized by THCa synthase from the biosynthetic reaction of CBGa (cannabigerolic acid) 

As you can see in the below picture, the evolution of these cannabinoids represented in their chemical structure, The right-hand side (B) of the image shows the conversion of CBGa to CBN to CBG. The left-hand side (A) shows the transformation of THCa and CBDa to THC and CBD, respectively. At every stage, the acidic carboxyl group gets eliminated. 

Moreover, the ‘big 6’ cannabinoids THC, CBD, CBG, CBN, CBC, and THCV begin their life in acidic forms. Hence, the CBGa converts into THCa, CBDa, and CBCa.  

• 

Medical Benefits of THCa

Cannabinoids research is growing like never before because of its promising qualities in therapeutic applications.

While several studies have begun to focus their attention on the medical benefits of THCA, the available research is anecdotal evidence and patient records. Some of the potential benefits could be:

• Anti-inflammatory
• Neuroprotective properties
• Antiemetic
• Anti-proliferative 
• Insomnia
• Pain management

Research on THCa-A

• The 2016 study¹⁶ brings forth some of its therapeutic potential benefits supported by Cell-based experiments on THCa-A. They could exert:

 (i) immunomodulatory, (ii) anti-inflammatory, (iii) neuroprotective, and (iv) antineoplastic effects

             The study also clarifies the unclearness about THCa-A:

1965 – First identification of THCa – Prof.Friedhelm Korte

1969 – Raphael Mecholam reported the existence of a second acid- the isomer of THCa, and named the former THCa-A and the latter THCa-B.

• In addition, the 2017 study¹⁷ reports that instability in the clinical application of THCa-A, despite growing interests in its therapeutic use. It adds that THCa-A lacks cannabimimetic effects, on the hypothesis that it has little binding potential with CB1.

• Contrary to the above study, a recent 2019 study¹⁸ investigated the possibility of dimerization of THCa-A to solve the issue of decarboxylative instability. This could by-pass the clinical applicability problems and support developments in pharmacological applications. 

Conclusion

• Cannabis research, its extracts, and cannabinoids have broadened the scope of pharmacology and clinical applications. It has promoted selective breeding of specific chemotypes and inventions of synthetic versions leading to improvements in the therapeutic index of cannabis. 

• Research on THCa and its therapeutic potential is in its infancy stage and could demonstrate positive outcomes.

References

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