The Cannabis plant produces an impressively diverse range of medicinal compounds, containing over 100 known cannabinoids and 200terpenoids contained in its resin. But the plant biosynthesizes cannabinoids in their acidic forms, such as THCA, CBDA, or CBGA, characterized by the presence of a carboxyl group attached to the phenolic ring. These acidic cannabinoids can lightning-fast be converted into the most ‘neutral’ and most medicinal proportions (THC, CBD, CBG etc.) under the influence of heat or prolonged storage that causes loss of the relatively unstable carbonyl group in the form of carbon dioxide. This process is called decarboxylation and is generally used in the preparation of spirits for oral or local use at low temperatures, without vaping or smoking.
A side effect of decarboxylation is the loss of terpenes, which are aromatic compounds of the plant that act synergistically with cannabinoids in relieving symptoms. Terpenes are volatile oils that evaporate at relatively low temperatures. Therefore, the creation of spirits for oral use at low temperature, with effective decarboxylation, reducing the loss of terpenes, is the ideal pharmaceutical approach. For spirits intended for vaping or intended for consumption at high temperature, pre-decarboxylation is unnecessary as this process occurs during digestion. This results in more preserved terpenes reaching the patient.
According to a 2013 study by ArnoHazekamp, university of Sienaand Leiden University, a comparison of decarboxylation methods revealed that a mild treatment of “bathing” the cannabis flower, at a low boiling temperature (98 – 100°C) for 5 minutes, did not lead to any particular deviations in the toxic-to-neutral cannabinoid ratio. In contrast, a kiln treatment with the material heated to 145°C for 30 minutes led to complete decarboxylation of the main identified cannabinoids. The THCA, the cannabigerolicacid (CBGA) and the cannabichromenicacid (CBCA) had all been fully converted toTHC, cannabigerol (CBG) and cannabichromene (CBC), respectively. Further conversion of THC to the main decomposed cannabinoidCBN), which inducing apocalyptic action, was created only in a small percentage during furnace treatment.
Compared to raw use, monoterpenes (the most volatile than terpenes) were reduced by about half of their original values even after the plant material was exposed to the “bath” of boiled water for just 5 minutes. After the most aggressive treatment in an oven, only traces of monoterpenes, terpineol, myrcene and terpinolene could be detected. The less volatile sesquiterpenes proved to be more resistant to mild ”bath’ treatment. However, most of them were lost in the furnace treatment and only traces of gamma-kadinenius and eudesma-3,7(11)-diene remained.
With this in mind, it seems that with effective pre-decarboxylation of the material while creating distillate, it will unfortunately result in the almost complete loss of monoterpenes. Heating the material to a temperature below 145°C for a period of more than 30 minutes, may be the ideal approach for the preservation of seskiterpenes and at the same time the creation of a medicinal distillate with the ideal toxic-to-neutral ratio for consumption at low temperature.
Due to the beneficial ‘accompanying effects’ that terpenes create in interaction with canabinoids, more research into terpene preservation techniques using different solvents and heating processes should become a goal of the pharmaceutical community. This includes experiments with the newest refined cold-extraction technologies that expose the distillate to just 100°C for 30 seconds as part of the solvent evaporation process. This minimal exposure offers the best method of preserving terpenes so far, although the distillate produced must go through decarboxylation with a strong ingestion temperature or other means.
by Sama’a Djomehri
 Luigi L Romano, Department of Pharmacy, University of Siena, Italy,
Arno Hazekamp, Plant Metabolomics group, Institute of Biology, Leiden University, The Netherlands, “Cannabis Oil: chemical evaluation of an upcoming cannabis-based medicine”, Cannabinoids, Vol 7, Issue 1, May 5, 2013