‘Terpenes are the chemicals which contribute to the flavor and effects profile in Cannabis, but we’re still early in the understanding of how.’ You’ve heard statements like this a thousand times and you’ve likely said it at least a few hundred times. But did you know that terps are an overwhelmingly huge class of chemicals, they’re a building block to cannabinoids from the cannabis plant, and that every plant and animal has the potential to make terpenes? And what do we even know about essential oil science? [[restructure questions are order to reflect document]] Let’s take a closer look at what’s meant when we say ‘terpene.’

A terpene is made of isoprene molecules, which makes it a hydrocarbon, just like butane. Think about LHO. I’m looking at you, Mr. H. Delbert. A hydrocarbon is composed of carbon and hydrogen, and if we add other elements to it – usually oxygen – it’s called a terpenoid. Think about beta caryophyllene versus beta-caryophyllene oxide. In the cannabis community (and in this article) the word terpene refers to terpenes and terpenoids. There are 11 primary terpenes found in cannabis, but 120 commonly found in the plant.

You’ve likely heard of monoterpenes and sesquiterpenes. These are references to how many isoprene molecules the terpene is made of. Each is five carbons, and we measure them similar to semitones in music. Each ‘full note’ is made of ten carbons. Monoterpenes – ‘mono’ meaning one – have ten carbons or two isoprenes. Sesquiterpenes have fifteen carbons, three isoprenes, or one and a half full notes. Diterpenes have 20 carbons, four isoprenes, or two full notes. The pattern continues through triterpenes, tetraterpenes, and polyterpenes. That last one can have hundreds of isoprenes, such as the basis of rubber.
The second layer of classification relates to how many cyclic, or circular rings, there are. In cannabis we see acyclic (no circles), monocyclic (one circle), bicyclic (two circles), and tricyclic (three circles). Cannabis produces terpenes, which are abundant in nature. Myrcene is the most abundant acyclic in nature, limonene the most abundant monocyclic, and pinene the most abundant bicyclic. There are few tricyclic terpenes found in cannabis, although THC can be classified as one.

Have you ever heard the term ‘terpinophilic’? It’s a reference to the structure of cannabinoids from cannabis: part terpene, part phenol. Don’t be concerned with the phenol element, but instead focus on what’s usually the left side of a cannabinoid molecule drawing. An easy comparison is CBD nearly having a limonene molecule as its terpene component. CBG has a nerol molecule as it’s terpene component. We find this pattern because terpenes and cannabinoids come from the same precursors.

In fact, their precursors are found throughout biology, as terpenes are ubiquitous to life. There are 25,000 documented terpenes and they’re all easily modified. In plants they act as signalling molecules and environmental modifiers. Examples can be as a fungicide to kill bad fungus in the soil, make an odour to attract an animal that will eat the insects off the plant, or even alter the earth’s atmosphere to encourage rain. In animal biology, terpenes are the basis of some hormones such as steroids we naturally produce. Farnesyl pyrophosphate, or FPP, is involved in the mitochondria (the ‘powerhouse’ of the cell, of course) and produces energy. It is also the precursor to sesquiterpenes in cannabis. Vitamin A is a terpene that has no odour