The unmistakable aroma of weed is the product of over 200 volatile compounds, each of which contributes earthy, citrus, diesel or various other tones to a cultivar’s scent. However, while many of these aromas are associated with terpenes, new research has revealed that the distinctive skunky smell of cannabis is actually derived from a totally different family of compounds that are also found in garlic.
New Smell Compounds Found In Cannabis
Presenting their findings in the journal ACS Omega, the study authors describe how they used techniques such as gas chromatography mass spectrometry to measure the aromatic properties of various strains of bud. In doing so, they discovered that a previously undetected class of volatile sulphur compounds (VSCs) plays a role in giving cannabis its smell[i].
In particular, a VSC called 3-methyl-2-butene-1-thiol – which the researchers simply refer to as VSC3 – was identified as the “primary odorant” in skunky smelling flowers. To confirm this, the authors attempted to recreate the smell of cannabis by assembling the plant’s ten most pungent compounds while excluding VSC3.
In doing so, they “found that although the scent was mildly reminiscent of the flower, it did not possess the pungent, skunk-like aroma.” However, the addition of VSC3 “resulted in an immediate olfactory change that strongly emulated the scent of the flower.”
According to the researchers, an analogue of VSC3 is also present in garlic, contributing to the herb’s aroma, while also endowing it with anti-cancer properties. Another compound called bis(3-methyl-2-butenyl) disulfide was also found to influence the smell of cannabis, and is virtually identical to a molecule in garlic that is believed to enhance cardiovascular health.
Based on these observations, the study authors write that “the structural similarities between VSCs in cannabis and garlic thus warrant further investigation to determine if the former possess similar health benefits to those of the latter.”
Why Does The Smell Of Cannabis Fade Over Time?
To determine how VSCs influence the strength of a plant’s aroma over time, the researchers measured the concentration of these compounds in several cultivars that they grew inside a greenhouse. Results indicated that VSCs were completely absent until about the seventh week of flowering, at which point several of these molecules began to appear in low amounts.
The skunky smell of these cannabis plants then strengthened over the following three weeks, correlating with an increase in the concentration of VSCs. At this point, the researchers harvested, dried and cured their bud for 11 days, noting that VSC levels “reached a maximum at the end of this process.” Unsurprisingly, the plants’ aroma was also at its strongest at this point.
However, concentrations of VSCs declined rapidly over the next ten days, corresponding with a noticeable decrease in scent. This, they say, indicates that these compounds are highly volatile, which would explain why cannabis has such a strong smell – especially when it is recently cured.
[i] Oswald IW, Ojeda MA, Pobanz RJ, Koby KA, Buchanan AJ, Del Rosso J, Guzman MA, Martin TJ. Identification of a New Family of Prenylated Volatile Sulfur Compounds in Cannabis Revealed by Comprehensive Two-Dimensional Gas Chromatography. ACS Omega. 2021 Nov 12. – https://pubs.acs.org/doi/10.1021/acsomega.1c04196