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Why Does Cannabis Smell Skunky? New compounds detected by 2D gas chromatography


As cannabis is legalized in more and more areas, it has grown in popularity as a medicinal and recreational drug. This plant has a pungent skunk odor that some people like but repels others. Now, researchers reporting in ACS Omega have discovered a new family of prenylated volatile sulfur compounds (CSVs) that give cannabis its characteristic skunky aroma. The results open up opportunities to study the molecules for medicinal purposes, the researchers said.

Cannabis sativa L. produces over 200 known aromatic compounds. Previous studies have mainly focused on terpenoids – molecules that smell from fuel to woody, citrus, or flowers. Different cultivars of cannabis have various mixtures of these compounds which contribute to their unique aromas. However, although terpenoids are the most abundant aromatic compounds in cannabis, there is little evidence that they provide the underlying skunk odor of many cultivars. Skunks use multiple VSCs in their smelly defense sprays, so Iain Oswald and his colleagues suspected that there might be similar molecules in cannabis. The team decided to use sensitive analytical techniques to find out.

The researchers analyzed the flowers of 13 cannabis cultivars using a custom 2D gas chromatography system with three different types of detectors. Then, a panel of four people rated the cultivars for spiciness on a scale of 0-10. The hottest, called Bacio Gelato, had the highest concentration of VSC. The team identified seven CSVs in this cultivar, some of which were also present in other cultivars. Five of the CSVs contained the prenyl functional group and had skunk or sulfur aromas. One compound in particular, 3-methyl-2-butene-1-thiol, called VSC3, was the most abundant VSC in the cultivars the panel reported to be the most pungent. This compound has previously been implicated in the flavor and aroma of “skunked beer” – beer that deteriorates after being exposed to UV light.

To confirm that VSC3 was the primary source of the skunk aroma, the team added it to a blend of 10 other major cannabis aromatics, producing a combined odor very similar to the characteristic odor of cannabis. They also detected VSC3 in cannabis concentrates, such as those used for vaping. Finally, in greenhouse experiments, researchers determined that prenylated VSCs increased significantly towards the end of the flowering phase of cannabis growth, peaked during curing, and then decreased dramatically after 10 days of storage. . Because the molecular structures of VSCs resemble compounds in garlic that have anticancer and cardioprotective effects, the new family of prenylated scent molecules should be studied for their medicinal properties, the researchers say.

Reference: “Identification of a new family of prenylated volatile sulfur compounds in Cannabis Revealed by Comprehensive Two-Dimensional Gas Chromatography ”by Iain WH Oswald, Marcos A. Ojeda, Ryan J. Pobanz, Kevin A. Koby, Anthony J. Buchanan, Josh Del Rosso, Mario A. Guzman and Thomas J. Martin, November 12 2021, ACS Omega.
DOI: 10.1021 / acsomega.1c04196

The authors do not mention any source of external funding for this study. Three of the authors have filed a patent related to the results.

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