Of the many active ingredients in marijuana, cannabinoids — the miracle molecules that deliver most of the medical efficacy of marijuana — are not the whole picture. Some cannabis consumers may be aware of terpenes, the cannabinoid-like chemicals that give herb such a pungent aroma.
What most do not know is that terpenes also deliver therapeutic relief, just like their cannabinoid cousins.
Terpenes are produced in special secretory cells within the trichomes of the plant, the nearly microscopic resinous stalks that cover the flowers and sometimes leaves. This is also where all cannabinoids, like THC and CBD, are created. About 20,000 terpenes exist in nature; more than 200 have been identified in cannabis (compared to 111 cannabinoids).
Like amino acids, terpenes are powerful building blocks within the plant’s physiology that aid in the production of vitamins, hormones, pigments, resins, and — yes, that most cherished part of the herb — cannabinoids. Cannabis plants release more terpenes when temperatures are higher.
Beyond odor, terpenes play several roles, including protecting the cannabis plant against predators like insects and animals. These special molecules constitute roughly 10 to 20 percent of the total pre-smoked resin in the trichome. It is estimated that 10 to 30 percent of smoke resin produced by marijuana comes from terpenes.
Myrcene, one of the most common terpenes in cannabis, produces earthy, balsamic, spicy, and clove-like odors. According to a 1997 study in Switzerland, it is the most abundant terpene in cannabis, sometimes composing up to 50 percent of the terpene volume in a cannabis plant. More important, myrcene has been found to be a precursor to many other terpenes in cannabis, meaning it helps form them.
It is found in more plants than simply marijuana, however. Myrcene is also produced in high amounts in mangos, basil, hops, lemon grass, and other plants. The amount of myrcene in a particular sample of cannabis determines if the plant will exhibit an indica or sativa effect.
Steep Hill Labs reports that marijuana samples with more than 0.5 percent myrcene will be indica, while those with less than 0.5 percent will be sativa. Myrcene is a constituent element of menthol and citronella and is arguably the most cited terpene.
The myrcene terpene offers many therapeutic effects, including relaxing muscles and killing pain. It is also an anti-depressant and anti-inflammatory. Like another terpene, limonene, myrcene has an effect on the permeability of cell membranes, meaning it can act as a regulator of other terpenes and cannabinoids, enhancing or buffering their effects (very similar to how CBD modulates the efficacy of THC).
Myrcene also possesses antimicrobial, antiseptic, antioxidant, and anti-carcinogen effects. Because it helps some other cannabinoids and terpenes pass through cell membranes, it allows more THC to reach brain cells, thus increasing the potency of cannabis. It’s the perfect example of the entourage effect in which both terpenes and cannabinoids work together synergistically to produce or enhance a particular therapeutic effect that could not be obtained from a single cannabinoid or terpene alone.
This powerful terpene also has been shown to slow bacterial growth, inhibit cell mutation (one of its roles in fighting cancer), suppress muscle spasms (making it a powerful tool in the fight against epilepsy and dystonia), and is even helpful for those suffering from psychosis because of its tranquilizing effect.
Unfortunately, the dearth of cannabis research — especially in the United States due to its Schedule I status — means that relatively little is known about the therapeutic effects of terpenes. What is known is very promising, however.
A 2007 study at the University of Jordan indicated that myrcene, working synergistically with another terpene, thujone, helps fight the symptoms of diabetes. This study was performed on mice and is a good example of the need for robust human trials to better identify the efficacy of this terpene and how it might help patients with life-altering conditions like diabetes.
A study by GW Pharmaceuticals in 2008 investigated the pain relieving properties of myrcene. It found that the terpene exhibits an analgesic effect that is opium-like in its mechanism — only without the addiction.
According to a comprehensive 2011 study published in the British Journal of Pharmacology entitled “Taming THC: Potential Cannabis Synergy and Phytocannabinoid-terpenoid Entourage Effects,” terpenes have been found to have medical efficacy typically considered to be delivered only by cannabinoids.
“Mice exposed to terpenoid odours inhaled from ambient air for [one hour] demonstrated profound effects on activity levels, suggesting a direct pharmacological effect on the brain, even at extremely low…concentrations.”
The study also found that myrcene relaxed muscles in mice and acted as a sleep aid at high doses.
“Together, these data would support the hypothesis that myrcene is a prominent sedative terpenoid in cannabis, and combined with THC, may produce the ‘couch-lock’ phenomenon.”
This detailed study, led by Dr. Ethan Russo of GW Pharmaceuticals, also identified the cannabinoids with which particular terpenes interact to produce targeted therapeutic effects — something Russo calls “phytocannabinoid-terpenoid synergy.”
The study identified myrcene as interacting with the following cannabinoids to produce medicinal benefits:
- CBD + Myrcene: Decreases inflammation, reduces pain, and fights cancer.
- THC + Myrcene: Reduces pain and relaxes muscles; also acts as a sedative and a “hypnotic.”
- CBG + Myrcene: Fights cancer.
Mangos: The Urban Legend
Because myrcene is present in high concentrations in mangos, it is responsible for the urban legend that consumption of mangos before smoking cannabis will enhance the effects of the THC in the herb. However, according to Steep Hill Labs, a respected marijuana testing facility in San Francisco, cannabis consumers who eat a fresh mango before smoking cannabis actually will increase its potency.
“For most people, the consumption of a fresh mango, 45 minutes before inhaling cannabis, will result in a faster onset of psychoactivity and greater intensity.”
Need for More Research
As with all aspects of the cannabis plant, more research is necessary to better understand the role of terpenes like myrcene and how they might be harnessed to combat common diseases and ailments. More needs to be understood about how myrcene, working in tandem with cannabinoids like CBD and CBG, fights cancerous tumors and reduces pain.
However, until marijuana is reclassified from Schedule I under the Controlled Substances Act, ample research and human trials can’t occur in the United States — and sick patients will continue to needlessly suffer.
This post was originally published on July 15, 2015, it was updated on October 5, 2017.