Decarboxylation: Cannabinoid activation and terpene retention

Have you ever wondered why it is necessary to heat cannabis before consuming it, whether smoking, vaporizing or cooking with this plant? The answer lies in a process called decarboxylation, which occurs through the application of heat, and which transforms cannabinoids into their most active forms, such as THC and CBD. CBD .

In this article, you will learn about the chemistry behind joints and marijuana recipes, and it will help you optimize your cannabis experience by understanding the importance of properly heating these compounds.

What is cannabinoid decarboxylation?

In the world of cannabis, decarboxylation is well known because it is a chemical process by which cannabinoids are converted from their acid form into their neutral form, which has the greatest effect on the body.

Why does cannabis have to be decarboxylated?

The cannabis plant produces cannabinoids in acid form represented with an “A” in the nomenclature. Examples of acidic cannabinoids are tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA). It appears that cannabinoids in acid form have no psychoactive properties and few therapeutic properties until they are converted to their neutral form through the chemical process of decarboxylation.

How does cannabinoid decarboxylation occur?

Decarboxylation can occur naturally over time, or it can be accelerated by applying heat [1]. The most universal form of cannabis decarboxylation is the joint. During the combustion of marijuana, heat converts THCA into tetrahydrocannabinol (THC), which is the compound we inhale, and which is responsible for the psychoactive effects of marijuana in our bodies. The same process occurs when heating CBDA from cannabis flowers. cannabis flowers which is converted into cannabidiol (CBD) after decarboxylation.

In this decarboxylation process, where one of the products is CO2 (carbon dioxide), the cannabinoids lose part of their mass. For example, THCA loses 12% of its weight when it changes to the neutral form THC [2].

Cannabinoid degradation: compounds derived from cannabinoids

There are other compounds that can form in the plant when cannabinoids are decarboxylated. These are produced not by decarboxylation, but from neutral cannabinoids and by exposure to air or light, through other chemical changes such as oxidation.

CBN – Cannabinol

Thus, once decarboxylated, THC can be oxidized to become cannabinol (CBN), which has fewer hydrogens and therefore more double bonds between carbons. CBN has been studied for its sedative properties, and appears to have less psychoactivity than THC.

Apparently, this degradation can also lead to CBD being converted to THC (delta-9-THC) or THC being oxidized to CBN or delta-8-THC (THC isomer) [1], before these compounds are consumed.

Now, the million dollar question: Can this step occur inside the body and if I consume CBD can I test positive for THC? And the ambiguous answer is: no, this step occurs outside the organism. Now, apparently, even without any scientific evidence, CBD consumption does not lead to a positive result in a THC test, but since cannabis products have so many compounds, there may be traces of THC that lead to a positive result.

THC decarboxylation and oxidation
Processes by which the different cannabinoid compounds are obtained: decarboxylation where THCA loses a carboxylic acid (COOH) and changes to its neutral form THC (indicated by a purple circle) andCO2 is produced. The oxidation where THC losing hydrogens and gaining double bonds is converted to CBN indicated by the purple arrow.

Delta-8-THC – Delta-8 tetrahydrocannabinol

Delta-8-THC is another cannabinoid that has gained fame lately that has a double bond between carbons eight and nine, while delta-9-THC has this double bond between carbons nine and ten.

Structure of delta-8-THC
Structure of delta-8-THC, with all carbons numbered and the double bond between carbons eight and nine marked with a purple arrow.

What happens to terpenes during decarboxylation?

One of the problems during the process of decarboxylation of cannabinoids is the loss of terpenes terpenes, which are compounds found in cannabis plants that contribute significantly to their aroma and flavor. Terpenes are volatile, which means that they evaporate easily when subjected to high temperatures, and this can lead to their loss during the decarboxylation process [3].

Some terpenes evaporate at temperatures as low as 20°C, although the boiling point of some of these monoterpenes is between 155-276°C and of some sesquiterpenes between 282-314°C [6].

Controlled heating is the simplest way to promote decarboxylation, preserve the highest terpene content and avoid degradation of cannabinoids. One of the advanced methods that allows better preservation of terpenes is the extraction with supercritical CO2, where temperatures between 40 and 60ºC are used.

Other compounds formed during heating

In cannabis extractions, it has been determined that the sum of THCA + THC + CBN concentrations is not constant, and is reduced to 78% after 60 minutes at 160°C. This is similar for other cannabinoids such as CBDA and CBGA, as in both cases the sum of their acidic and neutral forms is reduced to more than 90% after 60 minutes at 160°C. This suggests that there may be formation of as yet unidentified products during the heating of cannabis, in addition to evaporation of neutral forms at high temperatures [4].

Time and temperature for decarboxylation

The kinetics of decarboxylation, which refers to the rate and ratio of the chemical reactions taking place, has been studied under different temperature and time conditions.

The time-temperature binomial is fundamental in the cannabinoid decarboxylation process, as it affects the speed of conversion, the loss of terpenes, the degradation of cannabinoids and therefore the quality of the final product. If the temperature is increased, decarboxylation will occur more rapidly, but loss of volatile terpenes may also increase.

Decarboxylation follows first-order kinetics [4], meaning that the rate or speed of the reaction is proportional to the concentration of the reactant. In other words, the amount of neutral cannabinoids (such as CBD or THC) produced after decarboxylation is proportional to the amount of acidic cannabinoids (such as CBDA or THCA) present in the original sample.

At what temperature should cannabis be heated to obtain cannabinoids in their neutral form?

When the cannabis sample is subjected to elevated temperatures (approximately 160°C), there may be an increased loss of cannabinoids, which can be minimized if performed in the absence of oxygen [4].

The optimum temperature for decarboxylation has been determined to be around 200°C for a short time of 3 minutes. At lower temperatures, below 80°C, the conversion from the acidic to the neutral form is slower, and this rate increases with increasing temperature.

The conversion of THCA to THC is faster than that of CBDA to CBD or CBGA to CBG [4]. At a temperature of 120°C, THCA is completely decarboxylated after 90 minutes [4], whereas CBDA takes about one hour [5]. At a somewhat higher temperature of 160°C, only 20 minutes are required to achieve complete decarboxylation of THCA [4], whereas at 140°C, CBDA is converted to CBD within 30 minutes [5].

To decarboxylate the maximum of CBD, cannabis can be heated at a temperature of 140°C for 30 minutes. Under these conditions, CBDA is converted into CBD.

To avoid CBN accumulation, it is important to perform the conversion of THCA to THC at a temperature of 120°C for one hour, or at 105°C for 1-2 hours [5].

To decarboxylate the maximum THC, marijuana can be heated to a temperature of 160°C for 20 minutes. In this case, THCA is completely decarboxylated, becoming THC.

According to other evaluations, at a temperature of 150°C for 20 minutes, approximately 63% of CBDA is converted to CBD, 86% of THCA is converted to THC, and 63% of CBGA is converted to CBG [3].

If you want to decarboxylate the maximum THC, CBD and THC together in a single sample of cannabis, a balance must be found.

With the above data, at a temperature of 150°C for 20 minutes, the conversion of approximately 63% of CBDA to CBD, 86% of THCA to THC and 63% of CBGA to CBG is observed. These conditions could be a starting point to obtain a reasonable decarboxylation of the three main cannabinoids.

Vaporization temperatures

The boiling temperature of THC is around 157°C, while that of CBD is in the range of 160-180°C [4]. This is relevant for those wishing to vaporize cannabis, as these cannabinoids can be released and experienced through inhalation at appropriate temperatures.

Now that you know what decarboxylation is…

Thank you for joining me on this journey through the process of transformation of the components of cannabis during its heating. I hope that now you understand why whenever you want to get the properties of cannabis, it is subjected to heating, either in the form of a joint, or in recipes, such as the now legendary marijuana brownie .

But that’s not the end of the story. Now you may be wondering: what is the best method to decarboxylate and extract cannabinoids? Of course, marijuana can be heated in the oven at home, or in laboratories with sophisticated extraction equipment. This is how liquid hashish and marijuana butter are obtained.

Referencias
  1. Grijó, D.R., I.A.V. Osorio, and L. Cardozo-Filho, Supercritical extraction strategies using CO2 and ethanol to obtain cannabinoid compounds from Cannabis hybrid flowers. Journal of CO2 Utilization, 2018. 28: p. 174-180.
  2. Valizadeh Derakhshan, M., et al., Extraction of cannabinoids from Cannabis sativa L.(Hemp). Agriculture, 2021. 11(5): p. 384.
  3. Moreno, T., et al., Extraction of cannabinoids from hemp (Cannabis sativa L.) using high pressure solvents: An overview of different processing options. The Journal of Supercritical Fluids, 2020. 161: p. 104850.
  4. Moreno, T., P. Dyer, and S. Tallon, Cannabinoid decarboxylation: a comparative kinetic study. Industrial & Engineering Chemistry Research, 2020. 59(46): p. 20307-20315.
  5. Qamar, S., et al., Extraction of medicinal cannabinoids through supercritical carbon dioxide technologies: A review. Journal of Chromatography B, 2021. 1167: p. 122581.
  6. Eyal, A. M., Berneman Zeitouni, D., Tal, D., Schlesinger, D., Davidson, E. M., & Raz, N. (2022). Vapor pressure, vaping, and corrections to misconceptions related to medical cannabis’ active pharmaceutical ingredients’ physical properties and compositions. Cannabis and Cannabinoid Research.

Dra. Daniela Vergara
Investigadora y catedrática | Especialista en cultivos emergentes y consultora de cannabis

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