Prenylthiol, chemically 3-methyl-2-butene-1-thiol (often abbreviated 321MBT), is a small prenylated thiol. Oswald et al. (2021, ACS Omega) identified it as the key compound behind the classic skunk smell of cannabis, ending the long assumption that the smell came from terpenes. It is the same compound responsible for "lightstruck" or skunky beer.
In practice
Concentrations are tiny, too low for a standard terpene panel to see, yet enough to dominate aroma because the human nose detects thiols at extremely low levels. Detecting it takes specialised sulfur-selective gas chromatography, so it doesn't appear on routine COAs. In the 2021 study, related prenylated sulfur compounds were found across many cultivars, at different levels. That supports the grower observation that "skunk" is a genetic trait, not a product of feeding or curing tricks.
Don't confuse with
- Skunk (the animal): its spray uses different thiols, though the smell overlaps.
- Terpenes: present at much higher amounts, but not the skunk source.
- Skunk (cultivar name): a lineage name, not a chemical measurement.
Skunk is a generic name for a family of early hybrid cultivars from the 1970s and 1980s, and for the pungent, musky aroma they made famous.Terpenes are volatile hydrocarbon compounds built from five-carbon isoprene units; in cannabis they are made in the trichome heads and are a major part of aroma and flavour.A terpene test measures the individual terpenes and total terpene content of a sample, usually by GC-FID or GC-MS, reported in % w/w or mg/g.Volatile sulfur compounds (VSCs) are trace sulfur-containing aroma molecules, especially prenylated thiols, that give cannabis its skunky, gassy smell at concentrations far below terpenes.Gas chromatography (GC) separates volatile compounds in a heated gas stream; it is used for terpenes and residual solvents and decarboxylates acid cannabinoids in its hot inlet.Sulfur (S) is a secondary nutrient taken up as sulfate, used in the amino acids cysteine and methionine; deficiency yellows new growth fairly evenly.A terpene profile is the measured mix of terpenes in a sample, reported as each compound's % w/w and the total, used to describe and compare cultivar aroma chemistry.
