The decarboxylation of cannabinoids.
While the legal status of cannabis can vary significantly, extracts of the Cannabis plant (in the form of crude drugs, marijuana, hashish or hash oil) are the most widely consumed and popular recreational/medicinal botanical drug product in the world. Cannabis is now one of the most thoroughly studied plants with more than 100 cannabinoids isolated and identified, including delta 9, tetrahydrocannabinol (THC), cannabidiol (CBD) and cannabigerol (CBG). Studies of cannabis have investigated the potential benefits of phytocannabinoids for several disease states and symptoms (e.g. anticancer, antiemetic, sedative and palliative agents).
Phytocannabinoids- Carboxylic Acid (THC-A, CBD-A)
The cannabis plant manufactures phytocannabinoids in a carboxylic acid form (e.g. THC-A and CBD-A). These chemicals are not orally active (at least at CB-1 receptor sites) and they must be decarboxylated to be able to cross the blood-brain barrier. THC and CBD aren’t found in raw bud. Instead, raw bud contains tetrahydrocannabinolic acid and cannabidiolic acid (THCA and CBDA). In their natural state, THC-A and CBD-A don’t interact with the body in the ways you’re used to (THC-A won’t get you high and CBD-A won’t provide its potent medical benefits). During the drying process, the heat causes THC-A and CBD-A to chemically transform into THC and CBD. The efficient production of neutral cannabinoids (e.g. THC, CBD and CBG) from cannabis plant material is important for the development of dosage formulations to facilitate the successful medical use of cannabis. These neutral cannabinoids do not occur at significant concentrations in fresh plant material. Cannabis synthesizes primarily the carboxylic acid forms – namely D9-tetrahydrocannabinolic acid A (THC-A), cannabidiolic acid (CBD-A) and cannabigerolic acid (CBG-A). These acidic cannabinoids are thermally unstable and can be decarboxylated to neutral cannabinoids by exposure to light or heat (e.g. via smoking or baking). The decarboxylation of acidic phytocannabinoids can be understood using analytical chromatography (HPLC).
Decarboxylation CBD Hemp Oil
Decarboxylation is an essential step in the process of creating CBD hemp oil (medical cannabis, recreational cannabis, etc.), a popular supplement used for a variety of ailments. Decarboxylation occurs naturally (correlated with time/temperature treatment), resulting in the release of H2O and CO2. Cannabis plant material and cannabis extracts are heated to decarboxylate the cannabinoids (e.g. to convert CBD-A into CBD). Decarboxylation is an essential step when processing cannabis. It is a chemical reaction used to make cannabis extracts more potent. Decarboxylation is a process and chemical reaction that removes a carboxyl group from a molecule and releases carbon dioxide. Before cannabis is decarboxylated, naturally occurring CBD or THC are not present in the plant. These phytocannabinoids are found in an acidic state, better known as cannabidiolic acid (CBD-A) and tetrahydrocannabinolic acid (THC-A). The decarboxylation process converts these inactive components in cannabis (which are not psychoactive) into active components – converting CBD-A into CBD and THC-A into THC. The process of decarboxylation occurs naturally over time at ambient temperatures (so older cannabis is often already partly decarboxylated). It is noteworthy that the regular drying process typically isn’t enough to fully decarboxylate cannabis bud material and decarboxylation doesn’t happen naturally in the body. Decarboxylation is an important step for the efficient production of the major active components in cannabis – D9-tetrahydrocannabinol (THC), cannabidiol (CBD) and cannabigerol (CBG). These cannabinoids do not occur in significant concentrations in cannabis, but can be formed by decarboxylation of their corresponding acids (the predominant cannabinoids in the plant). The decarboxylation process is essential to unlocking all of the benefits for consumers. CBD is non-psychoactive, so even after decarboxylation users won’t receive the “high” of THC products – the process is simply to be able to activate the various therapeutic compounds of CBD. CBD oil can work as a treatment for various mental and physical illnesses (e.g. anxiety, cancer and chronic pain), as well as possessing beneficial properties (e.g. antioxidants, anti-inflammatories, anticonvulsants and antipsychotics). Understanding the kinetics of decarboxylation is important for phytocannabinoid isolation and dosage formulation for medical use. The diagram below from a 1990 publication has been used to describe the influence of temperature on THC decarboxylation.
A recent publication by Wang et al. (2016) gives a much more detailed summary of the decarboxylation of several cannabinoids (e.g. THC and CBD) over a range of temperatures and times. The study identified the most appropriate conditions for complete decarboxylation of the native cannabinoids. The diagram below summarises the effect of a variety of temperatures and times on the generation of CBD from CBDA. The optimal temperature for decarboxylation is about 110oC for about 1 hour. If decarboxylation proceeds for longer than this optimal period, other reactions can occur. The levels of decarboxylated cannabinoids can start to decrease and other chemicals can be generated. This paper discussed the generation of CBN (an oxidation product), D8-tetrahydrocannabinol and THCV during the decarboxylation process.
From: Wang, et al. Cannabis and Cannabinoid Research (2016) 262-271. Decarboxylation Study of Acidic Cannabinoids.
Decarboxylate Cannabis in Oven
The easiest and most convenient way to decarboxylate cannabis bud material is in an oven (e.g. 110oC for 1 hour). Special care has to be taken with heating (drying) the plant material or extract to avoid damaging the terpenes (the essential oils that give the cannabis plant its unique olfactory characteristics). There are a wide variety of terpenes and terpene combinations that create the odours and flavours (e.g. sour, bitter, sweet, spicy, etc.) that distinguish cannabis strains. Terpenes can also work in tandem with the cannabinoids to increase medical efficacy. As terpenes begin to degrade at 150oC, it is advisable to dry/decarboxylate below this temperature. Heating at lower temperatures has immense benefits for cannabis decarboxylation. Slowing down the process can assist cannabinoid extraction and retaining the distinctive flavor of a cannabis strain, which comes from naturally occurring oils called terpenes.
Cannabis plant material or cannabis extract can be “over-decarboxylated” if it is heavily heated for short periods of time. The cannabinoids and terpenes can be broken down with low heat for long periods of time until nothing is left. With higher temperatures, for shorter times, there is a risk of terpene and cannabinoid degradation on the surface of the marijuana. It is often better to heat slowly at a low temperature. In fully decarboxylated bud material, the THC and CBD in the extracts can be degraded if heat is used in subsequent extraction/processing steps.
Two primary stages in which decarboxylation
There are two primary stages in which decarboxylation can happen – when the flower is dried and when it is heated. When smoking or vaporizing, the extreme heat instantly activates the cannabinoids, which are absorbed into our bodies, producing an effect via our cannabinoid receptors. When cannabis is decarboxylated for edibles or extractions, these cannabinoids must be “activated” before consumption takes place. Once the cannabis plant material is successfully decarboxylated, it can be extracted to create potent tinctures or infused with various cooking oils, butter and lecithin. Correct decarboxylation will result in a fully activated extract where the integrity and potency of the cannabinoids and terpenes are maximised.
Author Dr. Craig Davis