Let’s be blunt: cannabis stinks. And hey, no judgment – we’re just saying there’s a reason it’s called skunk. But why must it smell so bad? The public demands answers – and a new study, published in the latest issue of the journal ACS Omega, has them.
There’s more than one thing that gives cannabis its tell-tale waft, and scientists have already isolated more than 200 of them. Most that have been studied so far belong to a family of compounds called terpenoids: smelly molecules, widespread in the natural world, that produce aromas ranging from fuel-like to woody or floral.
These terpenoids “can individually contribute upward of 50% of the aroma concentration,” explains the study. “For instance, OG Kush, a cannabis indica cultivar, possesses a strong, pungent, fuel-like aroma that arises from high concentrations of β-myrcene and β-caryophyllene. On the other hand, Jack Herer, a cannabis sativa cultivar, has high amounts of terpinolene and d-limonene, creating a woody and citrus aroma.”
But that’s not the whole story. Terpenoids “contribute strongly to the aroma of cannabis and give each cultivar its unique scent,” the study notes, but don’t account for “the chemical origins of the ‘skunk-like’ scent.” Even people who find the smell of cannabis pleasant would be hard-pressed to describe it as just citrusy or woody – so what else is at play?
It’s a hard question to answer, in part because the scent molecules involved are so complex, but it seems to come down to a family of chemical compounds known as volatile sulfur compounds, or VSCs. These are the same things that make Brussels sprouts taste gross and morning breath smell bad – and they’re also what make skunks smell so nasty. That’s actually one of the reasons the researchers decided to look for them in the cannabis plants – “the aroma of cannabis is often described as ‘skunk-like,’” explains the paper, “and as skunks are well known to possess several potent VSCs in their defensive aerosol spray, we suspected there could be similar compounds in cannabis.”
Their suspicions were right: they discovered “numerous” VSCs in the sample strains, some of which were brand new to them. Using a custom-built 2D gas chromatography system equipped with three different types of detectors, the team found that cannabis cultivars ranked by a panel of scientific sniffers as especially pungent also had higher concentrations of VSCs.
One of these, a compound called 3-methyl-2-butene-1-thiol, was particularly associated with the stinkiest of the samples – it “has an intense, sulfuric, skunky aroma even in extremely dilute concentrations,” the study reports, and is known for being the compound that gives “skunked beer” its distinctive wet cardboard flavor. When the team added this VSC to a cocktail of aroma compounds associated with cannabis, they were able to reproduce that skunky scent characteristic of the devil’s lettuce.
While “why does weed smell bad” may seem like a niche area of science, it could turn out to be surprisingly important. The VSCs responsible for the smell of cannabis are surprisingly similar in structure to compounds in garlic – compounds that may harbor anti-cancer and cardioprotective effects. Because of this, the researchers suggest investigating potential health benefits of cannabis.
If nothing else, the discovery might be the first step towards reducing the weed’s pungent aura – or, if the fancy takes you, intensifying it. After all, as the poet Radric Delantic Davis once said, “Kush, purp, strong dro; what I need cologne for? … Marijuana is my fragrance, probably smell it on my clothes.”