Tag Archives: decarboxylation

From The Lab

I Was Wrong… und das ist auch gut so!

By Dr. Markus Roggen
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I was wrong. And that’s a good thing! Based on all available data, I assumed that evaporating ethanol from a cannabis oil/ethanol solution would result in terpene loss. As it turns out, it doesn’t. There are so many beliefs and assumptions about cannabis: Cannabis cures cancer!1 Smoking cannabis causes cancer!2 Sativas help you sleep; Indicas make you creative!3,4 CBD is not psychoactive!5 But are these ‘facts’ backed by science? Have they been experimentally tested and validated?

I postulated a theory, designed experiments to validate it and evaluated the results. Simply putting “cannabis backed by science” on your label does not solve the problem. Science is not a marketing term. It’s not even a fixed term. The practice of science is multifaceted and sometimes confusing. It evolved from the traditional model of Inductivism, where observations are used in an iterative process to refine a law/theory that can generalize such observations.6 Closely related is Empiricism, which posits that knowledge can only come from observation. Rationalism, on the other hand, believes that certain truths can be directly grasped by one’s intellect.7 In the last century, the definition of science was changed from the method by which we study something, such as Inductivism or Rationalism, and refocused on the way we explain phenomena. It states that a theory should be considered scientific if, and only if, it is falsifiable.8 All that means is that not the way we study something is what makes it scientific, but the way we explain it.

I wonder how can we use empirical observations and rational deliberations to solve the questions surrounding cannabis? And more importantly, how can we form scientific theories that are falsifiable? Cannabis, the plant, the drug, has long been withheld from society by its legal status. As a result, much of what we know, in fact, the entire industry has thrived in the shadows away from rigorous research. It’s time for this to change. I am particularly concerned by the lack of fundamental research in the field. I am not even talking about large questions, like the potential medical benefit of the plant and its constituents. Those are for later. I’m talking about fundamental, mundane questions like how many lumens per square centimetre does the plant need for optimal THC production? What are the kinetics of cannabis extraction in different solvents? What are the thermodynamics of decarboxylation? Where do major cannabinoids differ or align in terms of water solubility and viscosity?

The lack of knowledge and data in the cannabis field puts us in the precarious position of potentially chasing the wrong goals, not to mention wasting enormous amounts of time and money. Here’s a recent example drawn from personal experience:Certainly, I cannot be the only one who has made an incorrect assumption based on anecdotes and incomplete data?

Some of the most common steps in cannabis oil production involve ethanol solutions. Ethanol is commonly removed from extraction material under reduced pressure and elevated heat in a rotary evaporator. I expected that this process would endanger the terpenes in the oil – a key component of product quality. My theory was that volatile terpenes9 would be lost in the rotary evaporator during ethanol10 removal. The close values of vapor pressure for terpenes and ethanol make this a reasonably assumed possibility.11 In the summer of 2018, I finally got the chance to test it. I designed experiments at different temperatures and pressures, neat and in solution, to quantify the terpene lost in ethanol evaporation. I also considered real life conditions and limitations of cannabis oil manufacturers. After all the experiments were done, the results unequivocally showed that terpenes do not evaporate in a rotary evaporator when ethanol is removed from cannabis extracts.12 As it turns out, I was wrong.

We, as an industry, need to start putting money and effort into fundamental cannabis research programs. But, at least I ran the experiments! I postulated a theory, designed experiments to validate it and evaluated the results. At this point, and only this point, can I conclude anything about my hypothesis, even if that is that my working theory needs to be revised. Certainly, I cannot be the only one who has made an incorrect assumption based on anecdotes and incomplete data?

There is a particular danger when using incomplete data to form conclusions. There are many striking examples in the medical literature and even the casual observer might know them. The case of hormone replacement therapy for menopause and the associated risks of cardiovascular diseases showed how observational studies and well-designed clinical trials can lead to contradicting results.13 In the thirties of the last century, lobotomy became a cure-all technique for mental health issues.14 Dr. Moniz even won the Nobel Prize in Medicine for it.15 And it must come as no surprise when WIRED states “that one generation’s Nobel Prize-winning cure is another generation’s worst nightmare.”16 And with today’s knowledge is impossible to consider mercury as a treatment for syphilis, but that is exactly what it was used as for many centuries.17 All those examples, but the last one in particular should “be a good example of the weight of tradition or habit in the medical practice, […] of the necessity and the difficulties to evaluate the treatments without error.”18 There is the danger that we as cannabis professionals fall into the same trap and believe the old stories and become dogmatic about cannabis’ potential.

We, as an industry, need to start putting money and effort into fundamental cannabis research programs. That might be by sponsoring academic research,19 building in-house research divisions,20 or even building research networks.21 I fully believe in the need for fundamental cannabis research, even the non-sexy aspects.22 Therefore, I set up just that: an independent research laboratory, focused on fundamental cannabis research where we can test our assumptions and validate our theories. Although, I alone cannot do it all. I likely will be wrong somewhere (again). So, please join me in this effort. Let’s make sure cannabis science progresses.


References

  1. No, it does not. There are preliminary in-situ studies that point at anti-cancer effects, but its more complicated. The therapeutic effects of Cannabis and cannabinoids: An update from the National Academies of Sciences, Engineering and Medicine report, Abrams, Donald I., European Journal of Internal Medicine, Volume 49, 7 – 11
  2. No, it does not. National Academies of Sciences, Engineering, and Medicine. 2017. The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research. Washington, DC: The National Academies Press. https://doi.org/10.17226/24625.
  3. No, it does not. The chemical profile of the plant dictates the biological effects on humans, not the shape of the leaf.  Justin T. Fischedick, Cannabis and Cannabinoid Research, Volume: 2 Issue 1: March 1, 2017
  4. Indica and Sativa are outdated terms. Piomelli D, Russo EB. The Cannabis sativa versus Cannabis indica debate: An Interview with Ethan Russo, MD. Cannabis Cannabinoid Res 2016; 1: 44–46.
  5. No, it is. CBD’s supposed “calming effects” is indeed a psychoactive effect. However, it is not intoxicating like THC. Russo E.B., Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects.Br. J. Pharmacol. 2011; 163: 1344-1364
  6. As attributed to Francis Bacon.
  7. See the work by philosopher Baruch Spinoza.
  8. As theorized by Karl Popper.
  9. Monoterpenes have a vapor pressure in the low to mid hundreds of Pascals at room temperature.
  10. Vapor pressure of 5.95 kPa at 20˚C.
  11. Furthermore, there is always the possibility of azeotropes in complex mixtures. Azeotropes are mixtures of two or more liquids that have different boiling points individually, but in mixture boil together.
  12. Terpene Retention via Rotary Evaporator Application Note, Heidolph North America
  13. https://www.pharmaceutical-journal.com/research/review-article/establishing-the-risk-related-to-hormone-replacement-therapy-and-cardiovascular-disease-in-women/20202066.article?firstPass=false
  14. https://psychcentral.com/blog/the-surprising-history-of-the-lobotomy/
  15. https://en.wikipedia.org/wiki/António_Egas_Moniz
  16. https://www.wired.com/2011/03/lobotomy-history/
  17. https://www.infezmed.it/media/journal/Vol_21_4_2013_10.pdf
  18. https://www.ncbi.nlm.nih.gov/pubmed/11625051
  19. Canopy Growth funds a professorship of cannabis science at UBC. Tilray collaborates with UCSD on a phase I/II clinical trial.
  20. For examples see: NIBR, PMISCIENCE.
  21. For examples see: CEMI, theAIRnet, Future Sky.
  22. Research that does not lead to short-term stock value spikes but long-term progress
The Practical Chemist

Potency Analysis of Cannabis and Derivative Products: Part 2

By Rebecca Stevens
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As mentioned in Part 1, the physiological effects of cannabis are mediated by a group of structurally related organic compounds known as cannabinoids. The cannabinoids are biosynthetically produced by a growing cannabis plant and Figure 1 details the biosynthetic pathways leading to some of the most important cannabinoids in plant material.

Potency figure 1
Figure 1: The biosynthetic pathway of phytocannabinoid production in cannabis has been deeply studied through isotopic labeling experiments

The analytical measurement of cannabinoids is important to ensure the safety and quality of cannabis as well as its extracts and edible formulations. Total cannabinoid levels can vary significantly between different cultivars and batches, from about 5% up to 20% or more by dry weight. Information on cannabinoid profiles can be used to tailor cultivars for specific effects and allows end users to select an appropriate dose.

Routine Analysis vs. Cannabinomics 

Several structurally analogous groups of cannabinoids exist. In total, structures have been assigned for more than 70 unique phytocannabinoids as of 2005 and the burgeoning field of cannabinomics seeks to comprehensively measure these compounds.¹

Considering practical potency analysis, the vast majority of cannabinoid content is accounted for by 10-12 compounds. These include Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD), cannabigerol (CBG), Δ9-tetrahydrocannabivarian (THCV), cannabidivarin (CBDV) and their respective carboxylic acid forms. The cannabinoids occur primarily as carboxylic acids in plant material. Decarboxylation occurs when heat is applied through smoking, vaporization or cooking thereby producing neutral cannabinoids which are more physiologically active.

Potency Analysis by HPLC and GC

Currently, HPLC and GC are the two most commonly used techniques for potency analysis. In the case of GC, the heat used to vaporize the injected sample causes decarboxylation of the native cannabinoid acids. Derivatization of the acids may help reduce decarboxylation but overall this adds another layer of complexity to the analysis² ³. HPLC is the method of choice for direct analysis of cannabinoid profiles and this technique will be discussed further.

A sample preparation method consisting of grinding/homogenization and alcohol extraction is commonly used for cannabis flower and extracts. It has been shown to provide good recovery and precision² ³. An aliquot of the resulting extract can then be diluted with an HPLC compatible solvent such as 25% water / 75% acetonitrile with 0.1% formic acid. The cannabinoids are not particularly water soluble and can precipitate if the aqueous percentage is too high.

To avoid peak distortion and shifting retention times the diluent and initial mobile phase composition should be reasonably well matched. Another approach is to make a smaller injection (1-2 µL) of a more dissimilar solvent. The addition of formic acid or ammonium formate buffer acidifies the mobile phase and keeps the cannabinoid acids protonated.

The protonated acids are neutral and thus well retained on a C18 type column, even at higher (~50% or greater) concentrations of organic solvent² ³.

Detection is most often done using UV absorbance. Two main types of UV detectors are available for HPLC, single wavelength and diode array. A diode array detector (DAD) measures absorbance across a range of wavelengths producing a spectrum at each point in a chromatogram while single wavelength detectors only monitor absorbance at a single user selected wavelength. The DAD is more expensive, but very useful for detecting coelutions and interferences.

References

  1. Chemical Constituents of Marijuana: The Complex Mixture of Natural Cannabinoids. Life Sciences, 78, (2005), pp. 539
  2. Development and Validation of a Reliable and Robust Method for the Analysis of Cannabinoids and Terpenes in Cannabis. Journal of AOAC International, 98, (2015), pp. 1503
  3. Innovative Development and Validation of an HPLC/DAD Method for the Qualitative and Quantitative Determination of Major Cannabinoids in Cannabis Plant Material. Journal of Chromatography B, 877, (2009), pp. 4115

Rebecca is an Applications Scientist at Restek Corporation and is eager to field any questions or comments on cannabis analysis, she can be reached by e-mail, rebecca.stevens@restek.com or by phone at 814-353-1300 (ext. 2154)