Cannabis was introduced into Western medicine in the 19th century by the Irish physician O’Shaughnessy, who became aware of the plant’s medical properties via the Indians. Cannabis, mostly in the form of ethanolic tinctures, was soon included in most pharmacopoeias and sold in the pharmacies of Western nations. This would remain the case until the 30s, when the global movement of criminalization started against the backdrop of increasing recreational use.
Wieland Peschel, from London University, notes in his recent experimental article that due to their early end, cannabis tinctures were never subjected to the modern pharmacological techniques of standardization and quality control. This is easy to understand considering that it was not until the 60s that the first cannabinoids started being elucidated.
Today, cannabis tinctures are regaining some popularity among non-smoking users, and there’s still a lack of knowledge about their chemical stability. This lack of information—Peschel reminds—is detrimental for a correct assessment of products’ shelf-lives, storage requirements, and analytical procedures needed to meet modern regulatory demands.
After considering these issues, the researcher went on to test different cannabinoid tinctures, created with traditional techniques and stored under ‘real world’ conditions. Different parts of cannabis plants were macerated using varied water and ethanol solutions. The liquids were then poured into common amber jars without a vacuum seal, and stored at different temperatures and light exposure conditions.
As expected, the higher the ethanolic (EtOH) content in the extracting liquids, the higher the total amount of THC and ratio of other cannabinoids were. For instance, the 40% EtOH and 20% EtOH formulations contained only 1/3 and 1/20 of the cannabinoid contents of the the traditional 80% EtOH tinctures. Regardless of the treatment, THC was always the major cannabinoid, with a usual 10:1 concentration to other cannabinoids.
Also not surprisingly, extracts from flowers, leaves, and roots yielded quite different results. Root extracts or cold water macerates were inefficient, whereas hot water allowed only for the extraction of non-cannabinoids. Pure flower extracts contained up to 10 times more THC than pure leaf extracts. More interesting perhaps was the finding that tinctures from finely ground leaves contained considerably higher concentrations of THC and phenolics than comparable extracts from intact leaves.
Profiles of tinctures from flowering tops (F), leaves (L = intact, GL = finely grond), or root (R) fresh and after 3 months of ‘fridge’ (4 °C/dark) or ‘shelf’ (15–25 °C/light). CW, cold water macerate; HW, hot water infusion, 40%, 60%, and 90% EtOH. Shown total levels of THC (THCtot), Cannabigerol (CBGtot), other cannabinoids (oCAN) and phenolic content (TPC).
After three months, flower tinctures stored at room temperature (20 °C) under moderate light exposure had lost twice as much cannabinoid content as those stored in the fridge (4 °C) in dark. The room temperature tinctures were also at more advanced stages of decarboxylation, with higher percentages of THCA and CBGA being converted to THC and CBG, than those stored in the fridge. In contrast, leaf extracts which had initially low total cannabinoid levels remained stable in both conditions, suggesting a chemical equilibrium or reduced decarboxylation process.
Shown absolute values for THCA, THC, CBN, and their sum (THCtot) in 60% tinctures from flowering tops (left) and ground leaves (right) over 15 months (4 °C/dark).
Chemical analysis at 15 months further revealed unexpected peaks of minor cannabinoids and flavonoids, which the author notes might pose a challenge to the correct labeling of cannabinoid tinctures.
Finally, the author examined the effects of a short heating (80 °C for 20 minutes, as in pasteurization) or a longer heating (70 °C for 2 hours). The procedures led to a moderate decrease—usually lower than 10%—in total cannabinoid and THC levels, especially in the 40% EtOH tinctures, but not to a significant decarboxylation. This suggests that cannabis tinctures are amenable to short heating operations, as is commonly practiced in industrial processes.
The study offers new information about the conditions of typical homemade cannabis tinctures, suggesting that protection from light, heat and oxygen is crucial for their stabilization. Total cannabinoid and THC levels, as well as the relative ratios of THCA/THC and CBGA/CBG (which are not usually analyzed), plus information about the extract solutions and the percentage of flower/leaf/root used, are important for determining the contents and quality of these tinctures. Some of these aspects, however, are less likely to matter in industrial preparations, where the extracts should already be fully decarboxylated.
Featured image via Flickr user Alice Carter.