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What Are Mono and Sesquiterpenes?

What Are Mono and Sesquiterpenes?

Posted by Matt Leonetti (he/him), NurseGrown Organics co-founder and farm manger on 8th Mar 2022

The chemical structure of terpinolene in 3D

I’m sure we’ve all heard the term terpene used, especially as it’s been popularized by the booming cannabis industry. Terpenes are aromatic oils that give plants their unique aromas.

Terpenes play a vital role in plants, attracting pollinators and repelling predators. Some support a plant’s immune system by keeping germs away, while others can help the plant recover from damage. But within this larger family of terpenes we find sub-categories such as mono- and sesquiterpenes. So, what are these, exactly?

The Chemistry

Terpenes are made mostly of hydrocarbons, an organic compound consisting of hydrogen (H) and carbon (C). The basic structure is a five carbon isoprene unit. An isoprene is a common organic compound, which, in its pure form, is a colorless volatile liquid.

The chemical structure of one isoprene unit.

Terpene hydrocarbons have a molecular formula of (C5H8)n – 5 carbon atoms and 8 hydrogen atoms. The n in the formula indicates the number of those isoprene units they have, and terpenes are classified based on their number of isoprene units.

Monoterpenes have 2 isoprene units and 10 carbon atoms. A sesquiterpene has 3 isoprene units and 15 carbon atoms. There are also diterpenes, triterpenes and tetraterpenes with ascending chemical structures.

To further complicate this, terpenes can be subdivided into acyclic and cyclic classes, which refers to their structure. Acyclic terpenes form a line – for example the terpene B-myrcene. Cyclic terpenes, like p-cymene, form rings. Both classes can be acyclic or contain rings and have many unique combinations.

Monoterpenes are generally isolated through steam distillation. They are colorless volatile oils that are less dense than water and have boiling points ranging from 150-190C. Monoterpenes are small molecules that evaporate quickly and are usually the first top note you’ll smell. When exposed to light, heat or air, they oxidize quickly and then are considered degraded.

Myrcene is believed to enhance the ability of THC to cross the blood brain barrier, giving certain cultivars their punch or slap.

This class of terpenes helps support the respiratory system as well as being responsible for many antiseptic, antibacterial and antiviral properties. They can act as air purifiers and deodorizers while also disrupting the body’s anti-inflammatory response and acting as cooling and soothing agents.

A very common monoterpene found in cannabis is myrcene. Myrcene is believed to enhance the ability of THC to cross the blood brain barrier, giving certain cultivars their punch or slap. Examples of monoterpenes are alpha-pinene, -3-carene, p-cymene, terpineol, and eucalyptol.

Sesquiterpenes are not as volatile as monoterpenes and can be generally isolated through distillation with steam or by extraction. They are colorless liquids of easily melted crystalline solids, with a boiling point of 230-300C. They have a weaker but more persistent odor than monoterpenes.

Sesquiterpenes are generally known for their calming properties. They also lend support to the immune system protecting us from harmful microbes, they can act as antioxidants and assist in cellular repair.

Breeders can now create cultivars with specific terpene profiles targeted to certain ailments.

The most common sesquiterpene in cannabis is B-caryophyllene. This is the only known terpene that binds to the cannabinoid receptor CB2. The action at this receptor is believed to enhance the pain relieving and anti-inflammatory actions of the cannabis plant.

Where We’re Headed

As research in the cannabis space moves forward, our greater understanding of cannabinoid and terpenoid synergy has allowed us, in a sense, to optimize cannabis therapies. Breeders can now create cultivars with specific terpene profiles targeted to certain ailments.

This is starting to dispel the myths of effects associated with sativa and indica cultivars. For example, one of the most well known sativa cultivars is Jack Herer. The dominant terpene is terpinolene, which has a sedating effect – exactly the opposite of the effect sativas are supposed to have, and highlights the importance of terpenes in cannabis. This shows why we shouldn’t be hung up on sativa or indica designations. Terpene profiles are far more significant.

As educators, we want to create well-informed cannabis consumers, and guide them about what to look for, and how to shop for their needs. Legalization has opened the doors for research, and helped broaden our understanding of the complexity of cannabis’s inherent compounds.

We look forward to the day when we have an even greater understanding of the therapeutic effects of our cultivars, and an expanded capacity to help as many medical cannabis patients as possible.

Photo by Jason Leung on Unsplash, Terpinolene – Creative Commons, Isoprene Unit – Almarie, Ahmed. (2020). Roles of Terpenoids in Essential Oils and Its Potential as Natural Weed Killers: Recent Developments. 10.5772/intechopen.91322.

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