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Comparison of the Cannabinoid and Terpene Profiles in Commercial Cannabis from Natural and Artificial Cultivation
John Decatur 1,
John Casali 2,
Tina Gordon 3,
Christine Skibola 4 and
Colin Nuckolls 1,*
Department of Chemistry, Columbia University, New York, NY 10027, USA
Huckleberry Hill Farms, 9415 Briceland Rd, Garberville, CA 95542, USA
Moonmade Farms, P.O. Box 5, Garberville, CA 95542, USA
Cosmic View, P.O. Box 1255, Novato, CA 94948, USA
Author to whom correspondence should be addressed.
Molecules 2023, 28(2), 833; https://doi.org/10.3390/molecules28020833
Received: 15 December 2022 / Revised: 3 January 2023 / Accepted: 11 January 2023 / Published: 13 January 2023
Interest in cultivating cannabis for medical and recreational purposes is increasing due to a dramatic shift in cannabis legislation worldwide. Therefore, a comprehensive understanding of the composition of secondary metabolites, cannabinoids, and terpenes grown in different environmental conditions is of primary importance for the medical and recreational use of cannabis. We compared the terpene and cannabinoid profiles using gas/liquid chromatography and mass spectrometry for commercial cannabis from genetically identical plants grown indoors using artificial light and artificially grown media or outdoors grown in living soil and natural sunlight. By analyzing the cannabinoids, we found significant variations in the metabolomic profile of cannabis for the different environments. Overall, for both cultivars, there were significantly greater oxidized and degraded cannabinoids in the indoor-grown samples. Moreover, the outdoor-grown samples had significantly more unusual cannabinoids, such as C4- and C6-THCA. There were also significant differences in the terpene profiles between indoor- and outdoor-grown cannabis. The outdoor samples had a greater preponderance of sesquiterpenes including β-caryophyllene, α-humulene, α-bergamotene, α-guaiene, and germacrene B relative to the indoor samples.
Until recently, cultivation and use of cannabis plants for medicinal, industrial, and recreational use were strictly prohibited and there is severely limited scientific research in this field [1,2]. However, due to recent shifts toward legalizing cannabis use in many locations, understanding its chemical diversity is of great importance for consumers and producers of cannabis. The bioactive properties of cannabis are derived from the plethora of secondary metabolites, which include cannabinoids, terpenoids, sterols, and flavonoids. Each of them has been identified and described across cannabis inflorescences, leaves, stem barks, and roots [3,4,5,6]. The chemical profile of particular metabolites has mainly been studied as a function of the plant’s genetics and environment. It stands to reason that the physiological effects and therapeutic benefit of different cannabis strains is linked to the diversity and the quantities of these secondary metabolites [7,8].
A common method in cannabis cultivation to avoid genetic variations is to grow genetically identical plants from clones. Moreover, by implementing biotechnological tools such as genetic engineering, it is possible to produce plants with overexpressed genes responsible for the biosynthesis of particular bioactive metabolites [7,9]. Environmental conditions such as mineral nutrition, temperature, humidity, soil bacteria, and light intensity/spectra are important factors affecting the chemical composition and secondary metabolism in cannabis plants [10,11,12,13]. The optimal mineral nutrients such as nitrogen (N), phosphorus (P), calcium (Ca), iron (Fe), and potassium (K) are essential for both the vegetation and flowering development stage of cannabis production [14,15,16,17,18,19]. For example, cannabis supplementation with nitrogen has been suggested for maximal inflorescence biomass production, while an increase in nitrogen supply may cause depletion in the levels of major cannabinoids such as Δ9-tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA) . THCA and CBDA are synthesized from cannabigerolic acid (CBGA), a common precursor, by THCA and CBDA synthase, respectively . Subsequently, they can be decarboxylated through various processes, such as heating, light exposure, or chemical reactions into CBD and THC. It has been reported that phosphorus-enhanced fertilizer increases the levels of CBD, CBG, and cannabinol (CBN), while decreasing THC . Interestingly, the concomitant N, P, and K supplementation can cause accumulation of CBG in flowers and depletion in the level of CBN/CBNA in both flowers and inflorescence leaves . Moreover, temperature, relative air humidity, and CO2 concentrations are other abiotic factors influencing cannabinoid biosynthesis . Significant variations in the cannabis plant morphology and secondary metabolism have also been reported in response to light intensity and quality [21,22,23,24].
Cannabis can be cultivated in open fields (outdoors), in greenhouses under a protected environment, or in controlled growing spaces (indoors). Outdoor cultivation exploits Mother Nature for light, temperature, and humidity, while indoor cultivation is energy-consuming and costly, mainly due to air conditioning, artificial lighting, heating, and ventilation . The vast majority of recent studies have been applied to fulfill the demand for optimal efficiency of the controlled growing system and yield maximization of cannabis in indoor conditions; therefore, there is limited information on the effect of outdoor cultivation on the quantity and variability of the secondary metabolites. During the period of prohibition, it was difficult to grow cannabis outdoors under optimized conditions, and as such, comparisons of outdoor- and indoor-grown cannabis are lacking in the scientific literature. This study compares the metabolic profile of commercial cannabis from two different cultivars, grown indoors using artificial light and artificially grown media, with samples having identical genetics but grown outdoors in living soil with sunlight. We found that in general, the commercial samples that were sun-grown (naturally) have less oxidized and degraded cannabinoids and more terpenes (quantity and type of terpenes), particularly the sesquiterpenes, than the genetically identical commercial samples grown indoors, under artificial lights utilizing artificial growth media.
2. Results and Discussion
Cannabis is an annual plant that can be grown efficiently indoors under controlled conditions or outdoors under full spectrum sunlight . Secondary metabolism in cannabis plants is influenced by several environmental cultivation conditions. To date, the effects of outdoor cultivation factors compared to indoor conditions on the cannabinoid and terpene profiles in cannabis have not been fully studied.
During inflorescence, the cannabis plant produces a plethora of cannabinoids and terpenes in the glandular trichome cells . It is staggering and remarkable the number of these molecules that the plant produces. There is also added complexity that the cannabinoids can be oxidized in a multitude of ways. This creates two types of cannabinoids. The first are ones that are intrinsic to the cannabis plant because they are made by a biological pathway in the plant . We refer to these as intrinsic cannabinoids. There are also other cannabinoids that are extrinsic to the cannabis plant that are created through subsequent reactions due to their environment, such as oxidation or photochemistry. We refer to these as extrinsic cannabinoids. The terpenes broadly fall into four main categories: monoterpenes (10 carbon), monoterpenoids (oxygenated terpenes), sesquiterpenes (15 carbon), and sesquiterpenoids (oxygenated sesquiterpenes) .
In this study, we used commercial cannabis samples that are cloned from a common parent but which are grown both indoor and outdoor under optimized conditions. The outdoor samples were grown in raised beds using a proprietary mixture of all-natural soil and composts under full sunlight. The indoor samples were grown under artificial light in a proprietary growth medium. The outdoor samples were stickier to the touch and were much more pungent than the indoor samples. The morphology and color of the flowers were similar. Each of the samples was from the same season to eliminate issues of large differences in age between the samples. Therefore, we can assess the importance of the two environments on the terpenes and cannabinoids metabolite compositions in two cultivars.