Understanding terpenes: Chemical properties and biosynthesis

Breaking down the science behind terpenes

Terpenes are naturally occurring volatile compounds responsible for the scent, flavor, and color of plants. They’re used in the natural world to protect organisms against insects and a host of other predators and pathogens. They communicate everything from food availability to the presence of a mate or potential danger.

Terpenes’ natural ability to deter insects and mitigate microorganisms resulted in their use across a range of commercial applications, including insecticides,  medicine and  essential oils. They are commonly sourced from such plants as lemon and other citrus fruits, thyme, and tea.

In addition to the vital role terpenes play in repelling predators and attracting us to the aroma and appearance of the cannabis plant, they are behind the plant’s anti-inflammatory, antiviral, antimicrobial, antiparasitic, and other medicinal properties.

As legalization expands and opens the door to further research, brands have already started moving away from distinguishing cultivars as either indica or sativa – labels that are now considered carryovers from the illicit market. Terpenes have begun to emerge as a more nuanced way for growers and producers to differentiate their products and explain to consumers the potential effects.

Isoprenoids, terpenoids, and terpene biosynthesis

Terpenes are part of the most extensive and varied class of volatile organic compounds known as isoprenoids. Isoprenoids are comprised of two or more units of isoprene, a hydrocarbon that contains a chemical structure of C5C8, or five carbon atoms and eight hydrogen atoms. Though terpenes are derived from a single isoprene unit, the terms are often used interchangeably.

Biosynthetic processes like photosynthesis and transpiration enable plants to convert oxygen, water, CO₂, and nutrients into energy – carbohydrates, proteins, and other primary metabolites – that they can use throughout their life cycle. During terpene biosynthesis, a single enzyme creates a reaction that links one part of a molecule to another and forms a closed ring, causing a variety of modifications that support growth and development. Secondary metabolites are among these modified compounds; they offer defense against pests and other stresses when a plant needs it most. An example of this is when a plant emits a scent that attracts pollinators to facilitate fertilization.

Terpenoids, a class of terpenes that defend medicinal and aromatic plants against diseases, are secondary metabolites that result from the introduction of oxygen. Included among secondary metabolites are flavonoids which also use scent, color, and flavor in plants to attract insect pollinators and regulate cell growth, among other functions.

Scientists have reportedly characterized anywhere from 20,000 to 80,000 classes of terpenoids. The sheer volume of terpenoid diversity is attributed to terpene synthase enzymes, which have the ability to create an entirely new profile by changing the chemical structure of a single amino acid.

Monoterpenes and sesquiterpenes in cannabis

Over 100 terpenes have been characterized across multiple cannabis genotypes and classified based on the number of isoprene units they possess. While there’s still much to be studied about these compounds, the majority of terpenes discovered in cannabis fall under two classes: monoterpenes and sesquiterpenes.

Monoterpenes have two isoprene units and are considered the smallest and most fragrant terpene. The primary function of monoterpenes is to attract pollinators or repel predators from feeding off plants through scent. They are used commercially in fragrances and repellants and are the primary ingredient in essential oils. The major monoterpenes in the cannabis plant include limonene, α-pinene, linalool, and β-myrcene.

Sesquiterpenes are larger and more stable than monoterpenes and are characterized by three isoprene units. Sesquiterpenes contribute to plant growth and serve as either a defense or attraction mechanism in response to environmental factors. They are used to treat migraines and bacterial infections. The most prominent sesquiterpene in cannabis is β-Caryophyllene.

Terpenes give each cannabis chemovar its unique flavor and aroma, and when combined with cannabinoids, they create a vast array of effects for growers and consumers.

While the relationship between humans and cannabis has existed for millennia, much of our understanding of the plant began just decades ago. One of the most exciting outcomes of legalization is the promise of more scientific research, which will go a long way toward helping producers cultivate plants and create products that serve consumers and patients in a variety of ways.

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