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      “Skunky” Cannabis: Environmental Odor Troubleshooting and the “Need-for-Speed”

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          Abstract

          Although the “skunky” odor characteristic of cannabis has been widely referenced, its cause has been historically misassigned to unspecified “skunky terpenes”. Recent reports from two independent research groups, the Koziel team (March and April 2021) and Oswald team (August and November 2021), have corrected this misassignment by linking the “skunky” character of industrial hemp and cannabis to 3-methyl-2-butene-1-thiol (321MBT). A recent USPTO patent application review clearly indicated that the Oswald team should take full credit for the discovery of this link with respect to cannabis. However, the August 19, 2021 publication of their patent application appears to be their formal public disclosure of 321MBT as the primary source odorant which is responsible for the targeted “skunky” odor. This date is well after the March and April 2021 public disclosures by the Koziel team for the 321MBT/“skunky” odor link relative to both cannabis and industrial hemp. This Viewpoint summarizes the investigative strategy leading to the public disclosure of this historically elusive link. It is presented from the perspective of the rapid multidimensional–gas chromatography–mass spectrometry–olfactometry (i.e., MDGC-MS-O) based odorant-prioritization “screening” approach, as applied by the Koziel team.

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          Most cited references20

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          Characterizing the Smell of Marijuana by Odor Impact of Volatile Compounds: An Application of Simultaneous Chemical and Sensory Analysis

          Recent US legislation permitting recreational use of marijuana in certain states brings the use of marijuana odor as probable cause for search and seizure to the forefront of forensic science, once again. This study showed the use of solid-phase microextraction with multidimensional gas chromatography—mass spectrometry and simultaneous human olfaction to characterize the total aroma of marijuana. The application of odor activity analysis offers an explanation as to why high volatile chemical concentration does not equate to most potent odor impact of a certain compound. This suggests that more attention should be focused on highly odorous compounds typically present in low concentrations, such as nonanal, decanol, o-cymene, benzaldehyde, which have more potent odor impact than previously reported marijuana headspace volatiles.
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            Identification of a New Family of Prenylated Volatile Sulfur Compounds in Cannabis Revealed by Comprehensive Two-Dimensional Gas Chromatography

            Cannabis sativa L. produces over 200 known secondary metabolites that contribute to its distinctive aroma. Studies on compounds traditionally associated with the scent of this plant have focused on those within the terpenoid class. These isoprene-derived compounds are ubiquitous in nature and are the major source of many plant odors. Nonetheless, there is little evidence that they provide the characteristic “skunk-like” aroma of cannabis . To uncover the chemical origins of this scent, we measured the aromatic properties of cannabis flowers and concentrated extracts using comprehensive two-dimensional gas chromatography equipped with time-of-flight mass spectrometry, flame ionization detection, and sulfur chemiluminescence. We discovered a new family of volatile sulfur compounds (VSCs) containing the prenyl (3-methylbut-2-en-1-yl) functional group that is responsible for this scent. In particular, the compound 3-methyl-2-butene-1-thiol was identified as the primary odorant. We then conducted an indoor greenhouse experiment to monitor the evolution of these compounds during the plant’s lifecycle and throughout the curing process. We found that the concentrations of these compounds increase substantially during the last weeks of the flowering stage, reach a maximum during curing, and then drop after just one week of storage. These results shed light on the chemical origins of the characteristic aroma of cannabis and how volatile sulfur compound production evolves during plant growth. Furthermore, the chemical similarity between this new family of VSCs and those found in garlic ( allium sativum ) suggests an opportunity to also investigate their potential health benefits.
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              Multidimensional gas chromatography-olfactometry for the identification and prioritization of malodors from confined animal feeding operations.

              Odor profiling efforts were directed at applying to high-density livestock operations some of the lessons learned in resolving past, highly diverse, odor-focused investigations in the consumer product industry. Solid-phase microextraction (SPME) was used for field air sampling of odorous air near and downwind of a beef cattle feedyard and a swine finisher barn in Texas. Multidimensional gas chromatography-olfactometry (MDGC-O) was utilized in an attempt to define and prioritize the basic building blocks of odor character associated with these livestock operations. Although scores of potential odorant volatiles have been previously identified in high-density livestock operations, the odor profile results developed herein suggest that only a very few of these may constitute the preponderance of the odor complaints associated with these environments. This appeared to be especially true for the case of increasing distance from both cattle feedyard and swine barn facilities, with p-cresol consistently taking on the dominant odor impact role with ever increasing distance. In contrast, at- or near-site odor profiles were shown to be much more complex, with many of the well-known lower tier odorant compounds rising in relative significance. For the cattle feedyard at- or near-site odor profiles, trimethylamine was shown to represent a significantly greater individual odor impact relative to the more often cited livestock odorants such as hydrogen sulfide, the organic sulfides, and volatile fatty acids. This study demonstrates that SPME combined with a MDGC-O-mass spectrometry system can be used for the sampling, identification, and prioritization of odors associated with livestock.
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                Author and article information

                Journal
                ACS Omega
                ACS Omega
                ao
                acsodf
                ACS Omega
                American Chemical Society
                2470-1343
                12 May 2022
                14 June 2022
                : 7
                : 23
                : 19043-19047
                Affiliations
                []Department of Agricultural and Biosystems Engineering, Iowa State University , Ames, Iowa 50011, United States
                []Byers Scientific , Bloomington, Indiana 47404, United States
                [§ ]Don Wright & Associates, LLC , Georgetown, Texas 78626, United States
                []Volatile Analysis Corporation , Grant, Alabama 35747, United States
                Author notes
                [* ]Email: koziel@ 123456iastate.edu . Tel.: +1-515-294-4206.
                [* ]Email: dwrigh256@ 123456gmail.com . Tel.: +1-512-750-1047.
                Author information
                https://orcid.org/0000-0002-2387-0354
                Article
                10.1021/acsomega.2c00517
                9201892
                35722010
                0e688a2d-d01d-4fba-952e-ac18ac5186de
                © 2022 The Authors. Published by American Chemical Society

                Permits non-commercial access and re-use, provided that author attribution and integrity are maintained; but does not permit creation of adaptations or other derivative works ( https://creativecommons.org/licenses/by-nc-nd/4.0/).

                History
                : 25 January 2022
                : 29 April 2022
                Funding
                Funded by: Iowa Agriculture and Home Economics Experiment Station, doi NA;
                Award ID: IOW05556
                Categories
                Viewpoint
                Custom metadata
                ao2c00517
                ao2c00517

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