As of February 2017, 29 states in the US (plus the District of Columbia; DC) have legislation, either in place or in progress, permitting the use of medical marijuana[A1] . Another 16 states have decriminalized possession[A2] , and 8 states (plus DC) have legalized marijuana[A3] for recreational use. With such changes in legislation, it is no surprise that North America’s cannabis sales increased by 30% between 2015 and 2016. Furthermore, they are projected to post an impressive 25% compound annual growth over the next 5 years, or by 2021. Tom Adams, editor-in-chief for ArcView Market Research said, “The only consumer industry categories I’ve seen reach $5 billion in annual spending and then post anything like 25% compound annual growth in the next five years are cable television (19%) in the 1990s and the broadband internet (29%) in the 2000s.”1
Two major contributors to the explosive increase in cannabis sales are edibles and other consumables (concentrates). In the first quarter of 2016, edibles and concentrates accounted for approximately 1/3 of total marijuana sales, up from 24% the year before.2 Specifically, the sale of edibles increased by 53% between Q1 of 2015 and Q1 of 2016, while sales of concentrates increased 125% comparing the same two periods.2 Edible products are very important to the medical marijuana industry; approximately 16–26% of patients opt to consume edibles because oral consumption eliminates exposure to the harmful by-products created by smoking the drug.3
Still other new products containing THC are in development, including alcoholic beverages that also contain cannabis, under development at Constellation Brands Inc. in Colorado.4 A second example, Cannabis Basics, produces low-THC, cannabis-based health and beauty product line. Recent success in legislative lobbying has afforded an opportunity to market these products, which contain ≤0.3%, in mainstream retail markets such as Kroger-owned grocery stores.5
Terpenes – the molecules responsible for cannabis effects
Terpenes, or isoprenoids, are fragrant molecules found in cannabis that contribute to its physiological and psychoactive effects.6 These molecules are volatile hydrocarbons built from repeating units of isoprene. In the plant kingdom, terpenes contribute to insect predation, protection from environmental stress, and defense against bacteria, fungi, and other pests. While there are >100 different terpenes found in cannabis,7 the primary terpenes include: α-pinene, linalool, myrcene, limonene, ocimene, terpinolene, terpineol, valencene, β-caryophyllene, geraniol, and humulene.6,7 In addition to terpenes, similar molecules called terpenoids may be found. These molecules are modified terpenes that have incorporated oxygen atoms or methyl groups. Terpenes (and terpenoids) act as building blocks for more complex molecules, such as the cannabinoids associated with the plant itself.
Terpenes and terpenoids, and the cannabinoids built from them, each have a unique set of pharmacological activities that vary widely, including pro-inflammatory, anti-inflammatory, anti-bacterial, anti-fungal, analgesic, anesthetic, sedative, muscle relaxant, anti-carcinogenic, and anti-seizure effects. Furthermore, many different combinations of two or more of these small molecules can produce synergistic effects. These multiple different compounds, in varying combinations and abundances, with a range of effects, leads to an exponential amount of variation in the net result of consuming a cannabis-containing edible or concentrate. These differences explain much of the variation experienced in not only the effects felt by its consumption, but also the scent of the product.
Between varietals of the Cannabis plant, terpenes and cannabinoids can vary in combination and abundance. On the plus side, the developing understanding of combination and synergy between these families of compounds has opened up opportunities for breeders to optimize plant strains and extractions for unique cannabis therapeutics. However, these tremendous variabilities create a considerable set of challenges for product makers and consumers alike.
The challenge – variation between products and batches
Analyses of the concentration and abundance of THC and the myriad terpenes in cannabis have shown tremendous variability in edibles and orally consumable products. These variations have potential implications in market value and quality control, as well as a unique set of legal concerns. For a patient, this variability can create difficulties with over- or under-dosing, leading to undesired side effects or lack of medical benefit, respectively. In one study that analyzed cannabis samples collected from dispensaries in Los Angeles, San Francisco, and Seattle, the researchers found that, of 75 tested products, only 17% were accurately labeled with regard to their THC content.8 Instead, 23% were under-labeled (contained more THC than described) and 60% were over-labeled (contained less THC than described). The lack of regulations for product labelling may contribute to this issue, but with a majority of products containing less THC than described, there is a real concern that they may not produce the desired medical benefit.
Clearly, an analytical system and clear, accurate product labelling are needed to improve this issue. Because the myriad terpenes and terpenoids influence the medical effects, a system sensitive and specific enough to capture minute quantities of these various molecules in a sample would provide the best description of a particular product or batch and provide the basis to predict how it will affect a user.
Importantly, there is no federal oversight currently in place to monitor the quality or safety of cannabis-based edibles or concentrates. Those states that have mandates for analytical testing leave laboratories with little guidance on the safety or legality of these products with regard to the concentrations of the active ingredients or the limits to various contaminants, such as heavy metals and pesticides. Furthermore, there is very little data to guide limits for contamination, which can ultimately result in delay in medicine access (if the limitations are too strict) or create potential risks (if the limitations are too lax.
Terpene analysis using headspace solid-phase microextraction (HS-SPME) and gas chromatography/ mass spectrometry (GC/MS)
Terpenes have high vapor pressures and are quite volatile. These properties make them excellent candidates for static headspace (HS) GC analysis. Although the available data on this subject is still quite limited, several projects have been designed to analyze the terpenes in cannabis samples. GERSTEL worked with MilliporeSigma to develop an HS-SPME method to detect three select terpenes: α-pinene, R-(+)-Limonene, and Linalool.9 Samples were spiked with a terpene cocktail, and volatile compounds were extracted with an HS-SPME technique on the GERSTEL MultiPurpose Autosampler, minimizing the “hands-on” time in processing. Although for these tests the cannabis sample was spiked with a terpene cocktail, the HS-SPME technique for terpene extraction provided detection with >90% accuracy for all three compounds. Because this technique is so sensitive, very little sample is required to acquire precise, reproducible, dependable results.
Sigma-Aldrich has used headspace SPME-GS/MS to analyze the terpenes in unprocessed, dried cannabis.10 In this analysis, terpenes were isolated using headspace SPME and separated on an Equity-1 capillary GC column. The compounds were identified using MS spectral matching against reference spectra in two different spectral libraries. For this sample, the most abundant terpenes included caryophyllene, α-pinene, and limonene.
Finally, a recent analysis was conducted at Penn State University to quantify the terpenes in Cannabis samples. 11 In this study, the GERSTEL MultiPurpose Autosampler was used to process the various standards and samples quickly and reproducibly. As part of the analysis, the researchers compared static headspace sampling with the more-sensitive HS-SPME extraction, followed by GC/MS. The reason for this comparison was to test whether static headspace analysis could accurately measure the wide range of terpene compounds with different volatility. Static headspace sampling was more selective for smaller, more-volatile compounds, whereas SPME was more sensitive for larger molecules. Overall, SPME was the more sensitive for terpene analysis.[A4]
In conclusion, the subject of terpene analysis in cannabis-containing edibles and concentrates is a quickly growing field of research and another important application for advanced, sensitive extraction methods and GC/MS analyses. Toward that end, GERSTEL has the tools needed to capture these important data, which will be extremely important in the development or regulations and laws to ensure that patients using medical marijuana can rely on their medication as confidently as they do for other pharmaceuticals. On a separate, but similarly important note, as we continue to analyze and learn about the important physiological and psychoactive synergistic effects of terpenes and how these compounds vary in the cannabis plant, we envision the capacity to cultivate and streamline this product into very specific, important therapeutics for a range of diseases.