Exploring the Chemical Makeup of Cannabis Extract by Method

This article reviews the chemical makeup of cannabis extracts and how they affect the human body. From terpenes to cannabinoids, this article takes a deep dive into the chemistry of cannabis extracts. It also demonstrates the opportunity for discovery and what we have yet to uncover.

Cannabis is widely known for tetrahydrocannabinol (THC) and cannabidiol (CBD), two prominent compounds found in relatively high concentrations in the flowers of Cannabis Sativa (1). As the legal cannabis industry develops, product offerings have expanded exponentially. Smoking cannabis flower is no longer the only option available to consumers, though it does maintain its position as the majority of product sales (Figure 1, click to enlarge).

Cannabis extraction has emerged as the gateway to product development. Various solvents are used to produce a number of different cannabis extracts, which can be sold as inhalable products or used to infuse ingestible and topical products. The chemical profile of the extract is dependent on the solvent used during the extraction, the parameters used during the extraction, as well as the input material.

Method-by-Method Chemical Analysis

Ethanol Extracted Cannabis Extracts

Ethanol extraction (2) is optimal for efficient cannabinoid extraction. The solubility of ethanol allows for all grades of cannabis plant matter to be used in the extraction, with nearly 100% of cannabinoids able to be extracted within 20 min. However, by optimizing for cannabinoids this extraction method sacrifices terpenoids, flavonoids, and other light compounds within cannabis that are lost in the process.

Warm or Room Temperature Ethanol Extracts

Warm or room temperature ethanol extracts contain:

⦁ Cannabinoids (THC, CBD, cannabigerol [CBG], and so on)

⦁ Plant pigments such as chlorophyll and carotenoids

⦁ Plant waxes

Because of the plant pigments and waxes, further refinement is necessary to remove these undesirable by-products. In turn, there is more loss of the delicate flavonoids and terpenoids leaving a highly concentrated extract full of phytocannabinoids. Some higher temperature ethanol extraction simultaneously decarboxylates the tetrahydrocannabinolic acid (THCA) turning it into THC. While we know the aforementioned compounds are found in the extract, we are still unsure of about 20–40% of the chemical makeup of cannabis extract depending on the cannabinoid potency. It is thought that warm or room temperature ethanol extracts are full of medically beneficial compounds and are best used in tinctures, capsules, and sublingual products.

Cryogenic Ethanol Extracts

Cryogenic ethanol extracts contain:

⦁ Cannabinoids

⦁ Some pigments

⦁ Some terpenes

⦁ Unknown other compounds

The cold temperatures of cryogenic ethanol extraction allow for efficient extraction of cannabinoids without the by-products such as pigments or waxes. The result is a high potency cannabinoid fraction that is not decarboxylated. Advanced cold extraction techniques are able to produce inhalable products called shatter, which is a hard-candy consistency product used as an inhalable. It is made up of 80–90% THCA crystals.

Ethanol extracts are growing in popularity because of their efficiency and potency, but lack in versatility. These extracts are often used to make high potency distillates as well as a variety of distillate infused ingestible products (Figure 2, click to enlarge).

Hydrocarbon Extracted Cannabis Extracts

Hydrocarbon extraction started as a low-tech but innovative extraction method in early medical and illicit markets. Its products, known as “concentrates” or “dabs,” have been a popular choice for many experienced cannabis users because of the amplified flavor and higher concentration of cannabinoids.

Hydrocarbon solvents are used under cold temperatures and under relatively low pressures. This is fast and captures the desirable components of the cannabis plant.

⦁Cannabinoids

⦁Terpenoids, especially mono-terpenes and mono-terpenoids

⦁Some plant waxes

Because of the higher potency of cannabinoids and terpenoids, hydrocarbon extracts often have potencies over 75% cannabinoids (Figure 3, click to enlarge).

While hydrocarbons quickly extract terpenes, aromatic hydrocarbons found in the plant, and cannabinoids extensive post-processing is required to remove the solvent from the extract. This requires more time and explosion-proof extraction and solvent removal equipment. The gravity of scalability and safety of this extraction method is significant.

CO₂ Extracted Cannabis Extract

Carbon dioxide is used in a number of other industries including hops oil extraction. Because of the nature of the cannabis plant, and the familiar similarities to hops, it was clear that CO₂ extraction would be a good fit for cannabis (4). CO₂ is easily manipulated into different phases using pressure and temperature. Naturally, this makes CO₂ one of the most versatile solvents in cannabis extraction.

Despite requiring a longer extraction time, CO₂ has the ability to selectively extract specific fractions from the plant because of its various phase properties (5). Subcritical and Supercritical CO₂ are the two most popular phases for cannabis extraction. Supercritical fluids maintain the properties of both liquid and gas. This gives CO₂ the ability to freely flow through the plant material, like a gas, while penetrating the trichomes and surface of the plant material, like a liquid. Subcritical CO₂ is operated at a lower temperature becoming a less efficient solvent overall, but focusing primarily on the volatile aromatic compounds such as terpenoids and terpenes. CO₂ is more efficient with extracting the full terpene profile of the plant including monoterpenes, sesquiterpenes, and a wide array of terpenoids, as demonstrated in a terpene fraction (Figure 4, click to enlarge).

Alternatively, CO₂ pressures can be ramped up to the supercritical phase to increase the efficiency of cannabinoid extraction. With that, the extraction time is dramatically reduced but more undesirable components such as waxes and pigments are also extracted. This reduces the crude potency of the extract, but a wax removal process known as “winterization” can be utilized to remove the lipids. This increases the potency of the extract. The terpene fraction and cannabinoid fractions are blended together to create high quality extract for vapes (Figure 5, click to enlarge).

In addition to the extraction solvent and parameters, the starting plant material also dictates the end result of the extract’s chemical profile. If starting with material that is low in terpenes but high in cannabinoids, the end result will be a low terpene high cannabinoid extract. If decarboxylated plant material is extracted with hydrocarbons, a THCA crystalline product will not be possible to produce as the THCA has already been converted to THC. There are many variables to the process that must be considered prior to extraction.

The Unknown and the Future

While testing methods have advanced significantly since the dawn of the modern era of cannabis, there remains a wide frontier of opportunity to discover and learn. Even in 2020, 10–30% of the total mass of a cannabis extract remains unidentified on a typical certificate of analysis (COA). This demonstrates that we are unable to identify a relatively large portion of the extract’s chemical makeup, or that it is not economically viable to do so. Generally, it is known that there are compounds such as esters, flavonoids, various pigments, alkaloids, and so on within cannabis extract. Despite the potential to influence experiences with cannabis, these compounds have yet to capture public interest or significant scientific inquiry with respect to product profiles and consumption.

Over time, discoveries have been made which demonstrate that each compound affects the human experience with cannabis. THC can enable euphoria, CBD reduces inflammation, limonene is energizing, CBG reduces anxiety (7), linalool is relaxing—yet none of these compounds work the same together as in isolation. Each compound influences the behavior of the entire network to provide synergistic effects. Through studying cannabis interactions with the human body, scientists have unveiled entire networks of systems within the human body, namely the endocannabinoid system (ECS). Our understanding of cannabis chemistry remains limited, and this new frontier provides ample opportunity for research and insights that can enable people to get more from this plant.

References

1. https://en.wikipedia.org/wiki/Cannabis_sativa.
2. https://www.edenlabs.com/coldfinger/ethanol-extraction-process/.
3. http://skyhighgardens.net/.
4. https://www.edenlabs.com/co2-extraction/co2-extraction-process/.
5. https://www.heylocannabis.com/post/what-is-rawx-why-does-heylo-cannabis-follow-this-method.
6. https://www.heylocannabis.com/strains.
7. https://www.heylocannabis.com/post/cbg-cannabigerol.
8. https://www.conflabs.com/

ABOUT THE GUEST COLUMNIST

LO FRIESEN is the founder, CEO, and Chief Extractor of Heylo. With a background in chemistry and clinical research, Lo was inspired to explore cannabis as medicine and to enter the emerging industry. She joined Eden Labs, a leading CO_² extraction equipment manufacturer to support and expand a Research and Development department. There she managed the development of their latest and greatest CO_² extraction system. In 2017, after working with Eden Labs and another cannabis processor, Lo launched Heylo with a mission to help people get more out of life with cannabis.

How to Cite this Article

L. Friesen, Cannabis Science and Technology 3(6), 14-20 (2020).