Supercritical CO2 Extraction May Cause Loss of Some Terpenes

At present, medicinal and recreational cannabis is most commonly consumed through inhalation, usually by smoking or vaporizing the cannabis flower, but other consumption methods are gaining popularity. Cannabis-derived extracts and concentrates are becoming increasingly popular, for example. These products tend to be created using solid-liquid extraction to create a cannabis concentrate that can be consumed via inhalation or oral ingestion. A recent study aimed at evaluating patterns of cannabis use in medicinal and recreational users found that cannabis concentrates accounted for 6.4% of self-reported usage data, third behind the more traditional inhalation (84.1%) and oral (8%) consumption methods.

Cannabis concentrates in the retail market

In recent years supercritical CO2 extraction (SC-CO2) has become an effective and popular approach for creating cannabis concentrates. Supercritical fluid extraction has been readily adopted by the cannabis industry, a process which has been aided by the popularity of the technique for creating other botanically derived concentrates. SC-CO2, is particularly well-suited for the production of cannabis concentrates as CO2 is cheap, non-toxic, works with many different types of organic compound, and is easy to separate and recover from the final extract.

Examining how the constituent cannabinoids and terpenes present in cannabis flower might be affected by being transformed into a cannabis concentrate via SC-CO2 is of great interest to producers and consumers alike. At the point of sale, cannabis is typically sold under a strain name that is thought to be indicative of its chemotype, and more specifically its cannabinoid and terpene content. This creates a level of expectation when a cannabis flower and a cannabis concentrate are being marketed under the same strain name: consumers assume they will have a similar chemotypic profile and therefore similar characteristics. This is an especially important consideration for those using cannabis for medicinal purposes as different chemotypes could have differing therapeutic effects.

Comparison of cannabis flower versus concentrate

Researchers from Washington State, U.S.A., recently published a study where they compared the cannabinoid and terpene content of the cannabis flower and the corresponding SC-CO2 extract for six common cannabis chemotypes. The group used a high-performance liquid chromatography/diode array detector (HPLC-DAD) method to quantify seven major cannabinoids, as well as gas chromatography-mass spectrometry (GC-MS) to quantify 42 different terpenes.

Five of the six chemotypes tested were what is known as type 1 plants, with the final chemotype being a type 2 plant. These types refer to the levels of two major cannabinoids, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), which are responsible for the majority of psychoactive and therapeutic properties of cannabis respectively. Type 1 plants are THC dominant, whereas type 2 plants usually show an equal ratio or slight leaning toward CBD. For the type 1 plants, they recorded a mean THCmax of 24% and a mean CBDmax of 0.2%. The corresponding cannabis concentrates for these type 1 chemotypes registered a mean THCmax of 73% and a mean CBDmax of 1.2%. The type 2 chemotype showed a similar trend, with the type 2 flower demonstrating a mean THCmax of 9% and CBDmax of 10%, which increased to 35% and 41% respectively in the concentrate. None of the other five cannabinoids that were tested for were present in significant amounts in either the flower or the concentrate.

All of the flower samples used were found to have similar terpenoid profiles with only minor variances in ratio. There are, however, large differences between the terpenoid profiles of the flower versus the concentrate samples. Monoterpenes, such as D-limonene and α-pinene, were present in lower levels in the concentrate compared to the flowers, by factors of 0.6 and 0.7 respectively. Many monoterpenes have relatively low vapor pressures and it is thought that the moderate heat involved in the SC-CO2 process may have caused a loss or a transformation of these compunds. 

The remaining terpenes studied, made up of sesquiterpenes and terpene alcohols, as well as a ketone and an ether, all experienced many-fold potency increases to varying degrees in the concentrates compared to the cannabis flowers. The most amplified component of the terpene profile was one bicyclic sesquiterpene which was found to be concentrated by a factor of 9.3 compared to the cannabis flower samples. The other terpenes varied between 4-fold and 9-fold increases in potency.

Concerns for concentrate use

The reduction in monoterpene content in the cannabis concentrates represents a big change in terpene fingerprint, and hence the whole chemotype, from the cannabis flowers to the cannabis concentrate. This means that the concentrate is not simply a more concentrated version of the flower. This change can alter the synergy between the cannabinoids and terpenes, which through the entourage effect, is thought to influence medicinal properties. As a result, the findings of this study may be of interest to those who support the movement for whole plant medicine, who believe that the entourage effect is key to creating more effective therapeutic cannabis strains. 

While there are some studies into terpene toxicity, they do not focus on terpenes consumed during cannabis use and so are of limited use to discussions surrounding the safety concerns brought about by this change in chemotype. Outside of the difference in terpene fingerprint, the large increase in THC content may also warrant further research into the potential health effects of acute and long-term use of high-potency cannabis such as this.