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Deep Dive: Terpenes Defined

Updated: Dec 30, 2023

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Welcome to Deep Dive: Terpenes Defined. This free 1,500-word training article from Higher Learning LV defines and clarifies terpenes, the aromatic molecules produced by cannabis/hemp/marijuana and more than 20,000 other botanical species on earth.


This article teaches the biochemical and evolutionary basics of terpenes, including their core evolutionary function and the role of molecular isoprenes. It concludes by summarizing two recent peer-reviewed scientific research studies regarding terpenes and their potential medicinal efficacy when consumed by humans or mammals.

A woman peers through the large fan leaf of a plant.
What are terpenes?

Terpenes Defined: The Big Picture

Terpenes Defined. Three primary families of wellness molecules are produced by the cannabis/hemp/marijuana plant species:

This Higher Learning LV article examines the major and minor terpenes derived from cannabis, including their general characteristics, wellness efficacies, and safety profiles.

A chart of several common terpenes and their molecular structures.
Some common terpenes.

Terpenes are Built on Isoprenes

Terpenes Defined. Terpenes, produced in the nearly microscopic glandular trichomes of the flowers of the plant, are the aromatic flavor molecules that give cannabis its sometimes pungent fragrance—especially during the latter stages of flowering, immediately prior to harvest. They are a class of lipid (fat) molecules that features a distinct and repeating set of five carbon atoms called an isoprene. Isoprenes combine to form larger and larger terpenes.


"Terpenes, produced in the nearly microscopic glandular trichomes of the flowers of the plant, are the aromatic flavor molecules that give cannabis its sometimes pungent fragrance."

Some terpenes, such as pinene, feature two nearly identical molecular siblings, called analogs or isomers. The scientific naming convention involves an alpha (alpha-pinene) and a beta (b-pinene).


Terpene Evolutionary Function

Terpenes Defined. From an evolutionary perspective, terpenes provide two essential functions to the plant species that produce them:

  1. Dissuade pests and predators (which perceive the aroma to be undesirable or toxic).

  2. Attract pollinating insects (which propagate the species, helping ensure its survival).

An air freshener hands in a car in Las Vegas that reads "Know your terpenes: a-Pinene"
Alpha-pinene: Most common terpene.

This same aroma is perceived as pleasant and acts as an attractant to humans and some mammals. Like pollinating insects, humans support the cannabis species through selective breeding, horticulture, and overall commercialization.


Terpene Molecular Types

Terpenes Defined. Beyond major and minor categories that indicate their relative presence in the cannabis genome, scientists categorize terpenes in several different categories based on their molecular and chemical characteristics.


"Hundreds of research studies have revealed significant potential medicinal efficacy delivered by a wide range of terpenes."

Isoprene molecules, often called isoprene units, are molecules that join with other molecules to form compounds. Isoprene molecules feature five carbon atoms with double bonds. The most simple terpene category, monoterpenes, features two isoprene molecules. The most sophisticated and molecularly heavy terpene type, tetraterpenes, feature eight isoprene units.


Terpene Research Studies

Terpenes Defined. Hundreds of research studies have revealed significant potential medicinal efficacy delivered by a wide range of terpenes. Below, summaries of two recent peer-reviewed studies regarding terpenes are provided to better acclimate students to the biochemical effects of terpenes when consumed by humans.


2020 Terpene Study

A December 2020 study entitled "The Cannabis Terpenes" that was published in the journal Molecules attempted to "morphologically describe sources of cannabis terpenes and to explain the biosynthesis and diversity of terpene profiles in different cannabis chemovars."

Some common terpenes.
Some common terpenes.

Reported the study: "Within the scope of this review, we provide the general background history of cannabis discovery and the importance of the terpenes. The taxonomy and morphology of the cannabis, particularly the localization of the terpenes, are discussed."


The researchers noted that different cannabis cultivars and chemovars (strains) "elicit different aromas with a greater link to product quality, retail price, and consumer preference." They also noted that the terpene composition, or profile, of a cannabis cultivar vary by a number of characteristics, including growing season, cultivar, anatomical section, environmental conditions, maturity, and method of analysis.


"Two distinct terpene descriptive clustering groups: One featuring earthy, woody, and herbal scents and another with citrus, lemon, sweet, and pungent aromas."

In addition, the study explained that a single cannabis or hemp plant could produce a variety of different terpene profiles during various stages of its growth. It reported that plants during their vegetative stage (prior to flowering) exhibit a terpene profile that features "a much lower proportion of monoterpenes than the flowering stage."


Interestingly, the study observed that the "molecular or biological functions of the terpenes are effective only when the concentration of the terpene in the full-spectrum cannabis extract is above 0.05 percent." It noted that its data reveals that the most common terpenes are myrcene and limonene.


"Data reveals that the most common terpenes are myrcene and limonene."

In terms of how humans perceive different cannabis strains and, thus, different terpene profiles, the study reported "two distinct descriptive clustering groups": The first included earthy, woody, and herbal scents, while the second featured descriptors such as "citrus, lemon, sweet, and pungent."


The study concluded that "recreational cannabis" has become more acceptable as a food ingredient and that terpenes have gained "high industrial attention in recent years." It noted that different cannabis genotypes feature variousa terpene profiles and that their medicinal efficacy could be enhanced by cannabinoids.


View the original study.

 

2019 Terpene Study

A November 2019 study entitled "Therapeutic and Medicinal Uses of Terpenes" that was published in the journal Medicinal Plants explored terpenes and their various molecular manifestations, including the two major categories, monoterpenes, sesquiterpenes, and more minor varieties like diterpenes, triterpenes, and tetraterpenes.

A chart showing the different types of terpenes.
Monoterpenes are most common.

The research focused on the medicinal properties of these various terpenes and terpene categories. Among these were antiviral, anticancer, antidiabetic, and antidepressant characteristics.


The study reported that terpenes "are the largest and most diverse group of naturally occurring compounds" on earth and that their categorization above is based on their number of molecular isoprene units. It noted that terpenes are found primarily in plants and that they form most of botanical essential oils. It identified common plant sources of terpenes as "tea, thyme, cannabis, Spanish sage, and citrus fruits (e.g., lemon, orange, mandarin)."


The research noted that terpenes are responsible for "the fragrance, taste, and pigment of plants." The researchers also explained that plants are not the sole source of terpenes. "Larger classes of terpenes, such as sterols and squalene, can be found in animals," reported the study.


Terpenes are responsible for "the fragrance, taste, and pigment of plants."

Antiviral activity was listed as among the most powerful capabilities of terpenes in humans and mammals. Efficacy of terpenes against viruses was found in the case of "three major human viruses—herpes simplex virus-1 (HSV1), dengue virus type 2, and Junin virus." The study reported that monoterpenes were found to be the most effective against viruses and listed the particular terpenes as "carvone, carveol limonene, alpha- and beta-pinene, caryophyllene, camphor, beta-ocimene," and a sesquiterpene called germacrene.

A sign at a shop in Los Angeles reads "terpenes"
What are terpenes?

This 2019 study was in the form of a literature review that analyzed data from previous studies on the subject. It found that a 2008 study analyzed the essential oil and terpene profiles from seven plants from Lebanon for antiviral activity ("HSV1 and severe acute respiratory syndrome corona virus, SARS CoV"). It found the best effects from the terpenes alpha- and beta-pinene, beta-ocimene, and cineole.


"A combination of monoterpenes, diterpenes, and sesquiterpenes can be effectively used to treat cancers that occur in colon, brain, prostate gland, and bones."

A 2009 study considered by the present investigation revealed similar results, suggesting that cineole, alpha-pinene, caryophyllene oxide, and sabinene were "major components of virucidal [antivirus] oils."


Terpenes were also reported to deliver potential anticancer efficacy by this study. "An early 1997 study concluded that a combination of monoterpenes, diterpenes, and sesquiterpenes can be effectively used to treat cancers that occur in colon, brain, prostate gland, and bones," reported the study. It noted that terpenes "inhibited the growth of prostate cancer cells and sensitized the tumor in such a way [that] it becomes susceptible to radiotherapy."

A woman holds a green cancer ribbon in her hands.
Do terpenes treat cancer?

It reported that the terpene limonene—available via citrus peels, orange peels, and cannabis and the second most common terpene on earth next to alpha-pinene—is "well recognized as an anticancer agent"and that it exhibits "strong cancer inhibition." A 2009 study considered showed that limonene "eliminates cancer cells by induction of apoptosis" (a genetically pre-programmed mechanisms by which cancer cells kill themselves via what is basically cellular suicide).


"Limonene can act as an excellent chemopreventive drug for cancer as it can be deposited in the body."

"Limonene can act as an excellent chemopreventive drug for cancer as it can be deposited in the body," reported the study. 2013 research considered revealed that limonene suppresses "the expression of breast tumor cyclin D1." The study also reported the efficacy of limonene for breast cancer, lung cancer, and pancreatic cancer (often involving the mechanism of apoptosis).


The research reported that the terpene thymoquinone "has been proved to be anticancerous against several cancers such as breast cancer, skin cancer, non–small cell lung cancer, bile duct cancer, and brain cancer" and that the mechanisms underlying this anticancer efficacy were apoptosis and cell cycle arrest.


In addition, the study discussed how terpenes may offer medicinal and therapeutic support for other diseases and conditions, including depression, diabetes.


View the original study.

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