Terpenes. Everybody has interacted with them in one form or another. If you’ve ever cleaned the house, washed your face, sniffed a flower or walked outside, you have unknowingly ingested terpenes. Terpenes are small, aromatic compounds found in all plants and even some insects. They give plants their smell and also have associated therapeutic properties. In the world of cannabis, terpenes are kind of a big deal.
Research scientists believe that terpenes in cannabis are most likely responsible for the varying effects on mood and the therapeutic potential that different cannabis varieties may exhibit. Cannabis consumers want the terps, not only for enhanced aroma, but also for enhanced effect. Manufacturers, responding to consumer demand, have now made it common practice to add terpenes to edibles, concentrates, and extracts so that they may have greater appeal for consumers. However, not all terpenes are created equal and more terpenes is not always synonymous with better effects. When vetting products that have “added terpenes” ask the following questions: Where did the additive terpenes come from; synthetic, botanical or cannabis? How were they extracted? What solvent are they suspended in? What concentrations of terpenes exist in the product?
Additive terpenes typically come from one of three sources: cannabis, botanical (fruits and/or other plants), or synthetic aka made in a laboratory setting. In the cannabis market, most terpenes added to enhance concentrates and extracts are from botanical sources. For example, a common terpene in cannabis – limonene – is also abundantly found in the rinds of citrus fruits. Extraction technicians can extract limonene from citrus fruits. Most often, terpenes are removed from their botanical sources by a process called steam distillation.
Distillation is the evaporation and subsequent condensation of a liquid to produce concentrated pieces of the original plant material’s composition. Distillation produces essential oil as well as hydrosol. Many terpenes sold on the market are hydrosols: aromatic “floral” waters that contain many different compounds, very few of them actual terpenes. It is important to note that hydrosols are unfit for human consumption via inhalation.
Steam distillation uses the heating and condensation of water to distill essential oil and hydrosol from plant material. Because this process uses heat, terpenes are often thermally degraded. Terpenes are incredibly volatile compounds – they easily evaporate into air and are reactive even at low temperatures. The hot steam used in distillation will decompose terpenes and may even lead to the creation of new compounds in the process, such as the highly reactive aldehydes and esters. Aldehydes and esters are organic compounds that are often aromatic and may be mistaken for terpenes because of their smell.
This is all to say that when you extract terpenes with heat, you degrade the terpenes. Therefore, the oil cells present in distilled oils and hydrosols do not carry the same compounds as oil cells present in the original plant material. This means that the effects of these extracted terpenes will differ from their associated properties observed when they are consumed in the plant material.
Despite the thermal degradation, extracted terpenes sold on the market do contain concentrated compounds including denatured terpenes, aldehydes, esters and phenols. At this point, we don’t have enough research to conclusively state that consuming these compounds, especially via inhalation, in such high concentration, is safe.
A 2017 study titled, “Toxicant Formation in Dabbing: The Terpene Story”, found that when terpenes were exposed to the temperatures needed to ‘dab’, the terpenes transformed into harmful compounds, such as the carcinogenic compound benzene. These research findings suggest a cause for concern when adding terpenes to concentrates and extracts designed to be heated and inhaled.
Terpenes are important to the therapeutic potential of cannabis. They not only have an impact on the aroma of varieties, but can also have a physiological impact as well as share synergistic potential with cannabinoids. However, the thermal extractions of terpenes from botanical sources, cannabis and otherwise, create relics of the original compounds. These terpene extracts may be unhealthy and even dangerous when heated at such high temperatures and inhaled.
To have a cannabis experience that is terpene centric, try consuming cannabis flower in a dry plant vaporizer programmed to the lowest temperature setting. This will allow you to gently heat and inhale terpenes in their original form and concentrations, reaping the therapeutic and aromatic benefits of the flower.
The next time you assess a cannabis vape pen or a cannabis concentrate intended for inhalation, look for the language “added terpenes” and inquire as to their origin. While marketing may have us believe that a higher concentration of terpenes equates to better quality, it could mean the opposite.
For more information on this topic, listen to this episode from Periodic Effects podcast on Terpenes.
Meehan-Atrash, Jiries, et al. “Toxicant Formation in Dabbing: The Terpene Story.” ACS Omega, vol. 2, no. 9, 2017, pp. 6112–6117., doi:10.1021/acsomega.7b01130.
Morrow, Kenneth. “Not All Terpenes Are Created Equal.” Cannabis Business Times, magazine.cannabisbusinesstimes.com/article/november-2019/terpenes-hydrosols-essential-oils-cannabis-production.aspx.