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Mythical Myrcene • Grow Magazine

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By Robert C. Clarke

“I used to feel high, now I just fall asleep.”

Terpenes are the talk of Cannabis Town and myrcene crosses our lips more than most. Symbolic of the many questions surrounding modern sinsemilla, myrcene is both in your face, yet elusive, blamed for couch lock while touted as an effective sleep aid, plays a key role in the “indica versus sativa” debate, proves challenging for breeders, and has become a recent focus of plant patents. But what do we really know about this mythical monoterpene?

UBIQUITOUS MYRCENE

Myrcene is the most commonly reported aromatic compound in Cannabis as well as its closely related genus Humulus or hop. The genes coding for myrcene biosynthesis must have evolved long before their deep time divergence from a common ancestor into separate genera. Myrcene is produced by many plants and can be found in significant quantities in basil, bay, parsley, lavender, lemongrass, sage, and thyme leaves, as well as pine needles and mango fruits, to name a few. Because it is found in Cannabis worldwide, including in wild populations and landraces as well as fiber and seed hemp varieties, it is impossible to determine with certainty a geographical origin for the myrcene content of modern sinsemilla.

Laboratory analyses of sinsemilla flowers reveal that myrcene is the most common terpene, followed by caryophyllene and humulene, limonene, terpinolene, the pinenes, ocimene, and linalool. Although these and many other terpenes have been identified in Cannabis, myrcene is dominant in more than half of present-day cultivars. There are dozens of terpenes found in Cannabis plants, and in some varieties other terpenes are dominant, indicating that the majority of widely available commercial sinsemilla lacks potential aromatic diversity.

Afghan landrace introductions are in part responsible for the prevalence of myrcene in modern cultivars, the vast majority of which are descendant from ’80s Afghan hybrid crosses. When it is the dominant terpene, myrcene levels range from 25.0 to 80.0% of the essential oil. High myrcene levels are reported in Skunk No. 1, Bubba Kush, OG Kush, and 9 Lb. Hammer (an OG Kush hybrid), Blue Dream (a Blueberry x Haze hybrid), Granddaddy Purple (with Big Bud heritage), Grape Ape (a descendant from an Afghan x Skunk No. 1 cross), Tangie (a California Orange x Skunk No. 1 hybrid), and the seminal Dutch cultivar White Widow (a Northern Lights relative). Myrcene is also found in the high-CBD sinsemilla cultivars Cannatonic, Harlequin, and Remedy, among others.

All of these varieties share Afghan landrace ancestry, but so do the vast majority of modern sinsemilla hybrids, some of whose chemotypes are dominated by other terpenes and are typically low in myrcene. Myrcene was already present in New World landraces and early homegrown populations long before Afghan arrived. The introduction of Afghan landraces resulted in more profound agronomic outcomes including compact plants with more branched structure, earlier maturation, increased resin production, and vulnerability to bud rot and mildew. Myrcene content is upheld as defining “indica” varieties that are characterized as high in myrcene, and “sativa” varieties that are relatively lower in myrcene. In fact, myrcene levels can be high and even dominant in sinsemilla varieties characterized as either predominantly indica or predominantly sativa, and there are few if any correlations between myrcene content and the popularized “indica versus sativa” classifications.

FLEETING MYRCENE

Myrcene is highly volatile and fugitive. Its molecules continually escape into the air, and myrcene accumulates in Cannabis resin glands simply because biosynthesis exceeds evaporation rate. When a flower is harvested, terpene biosynthesis ceases, but evaporation continues apace. Large amounts of terpenes are lost during drying. More disappear with curing, and myrcene can even escape through plastic zip bag and canning jar seals. The remaining myrcene degrades into other monoterpenes with differing fragrances and flavors.

At room temperature, myrcene-dominant aromas change over time and eventually disappear entirely, making high-myrcene cultivars difficult to assign to a single fragrance and flavor group. Terpene content decreases until the flowers are properly dried, cured, packaged, and stored. Each time you smell a drying flower, it offers but a fleeting glimpse of an ever-changing aromatic landscape, never to be revisited. Although myrcene was often the predominant terpene at harvest, by the time exported cannabis reached distant destinations, the majority had disappeared during transport. Exceptionally high levels of myrcene and other terpenes in fresh sinsemilla are the main reason modern cannabis is different!

MYRCENE AROMAS

Myrcene alone presents an especially complex odor characterized by fragrance and flavoring experts as a blend of spicy, musky, earthy, peppery, balsamic, and root-like aromas with herbaceous, woody, rose, clove, citrus, tropical fruit, mango, grape, peach, vanilla, wine, mint, hop, celery, and carrot nuances. Fruits and flowers, herbs and spices, and earthy dankness all rolled into one. Wow!

Skunk No. 1 essential oil typically contains 50.0 to 70.0% myrcene with limonene as the second terpene. Skunk No. 1 is a descendant of Colombian, Mexican, and Afghan landrace parents and presents a classic example of a hybrid New World homegrown marijuana lineage crossed with an Old World Afghan hashish landrace — the seminal heritage shared by the majority of today’s sinsemilla cultivars. Skunk No. 1 was also a cornerstone building block in the genetic heritage of many cultivars, further spreading myrcene as the dominant terpene.

The fragrance and flavor of myrcene-rich Skunk No. 1 is commonly described by aficionados as sweet, fruity, and floral with citrus notes, a bit of musty earthy dankness, and a hint of cedar spiciness. Myrcene is likely responsible for the sweet fruity and floral aromas and limonene for the citrus notes, while its earthiness may come from the Afghan side, and spiciness from its New World parents. Skunk No. 1 is respected for its cerebral high and somewhat energetic effects at onset, followed by deep meditative relaxation, essentially a “best of both worlds” scenario. High myrcene content could account for both the initial stimulation as well as eventual sedation.

Magical Nighttime Landscape With Sparkly Lights

COUCH LOCK

Myrcene is attributed with causing the sedative and somewhat dissociative suite of effects called “couch lock,” commonly experienced with modern sinsemilla. However, there are additional differences between sinsemilla and traditional imported weed. Today’s sinsemilla is more potent than seedy imports; the effects produced by THC are often biphasic with initial stimulation followed by relaxation, especially after the peak experience begins to fade.

Media reports often claim that “indica” varieties produce higher levels of myrcene, which accounts for their more sedative and relaxing effects, and also the corollary that “sativa” varieties are characteristically lower in myrcene and are therefore more stimulating. Certainly, mental escape, relaxed tranquility, and proper sleep are valuable outcomes of cannabis use, and these effects are what many people want and have come to expect. Yet others seek a more cerebral, energetic and euphoric high to enhance creative thought and motion. Variations in THC, CBD, and minor cannabinoid levels and ratios do not sufficiently account for the wide range of effects experienced from cannabis use, and the aromatic terpenes are likely responsible. No cannabis variety produces only a single aromatic compound, and effects are based on the collective actions of a complex suite of terpenes. Myrcene-rich varieties can be either more corporeal or more cerebral depending on both their cannabinoid content and the presence of additional terpenes.

There is however, significant anecdotal evidence alluding to myrcene’s relaxing qualities. Historical accounts indicate that hop pickers slept remarkably well after a day of harvesting, and babies slumbered peacefully in their hammocks suspended between the rows. Hungarian hemp harvesters lay their babies in the shaded interior of conical tent-like stooks of drying stalks, where they sleep soundly while their parents work. “Dream pillows” stuffed with aromatic dried hops rich in myrcene are used to promote sound sleep. Highly volatile myrcene is likely the common denominator throughout these Cannabaceaean encounters.

MEDICINAL MYRCENE

Lemongrass is both myrcene- and limonene-rich and has been used in traditional Asian folk medicine for centuries. Today, lemongrass essential oil is included in popular infused drinks to add aroma and flavor as well as enhance their relaxing and sedative properties. Potential therapeutic uses of myrcene also rely on its sedative, analgesic, and muscle-relaxant effects; as well as its antiseptic, antibiotic, antimicrobial, antioxidant, antispasmodic, anti-depressant, anti-inflammatory, and anti-mutagenic properties shared by other terpenes.

A single sinsemilla flower can contain more than 50 terpenes (albeit most in only trace amounts) and synergistic relationships modifying the effects of the primary active cannabinoids are likely. Along with myrcene, other major terpenes such as caryophyllene and the pinenes may individually have relaxant properties, and varieties combining all three may be more synergistically effective for reducing stressful anxiety than any one alone.

However, mouse studies administering much larger doses of myrcene than the levels found in cannabis indicate that although it has strong analgesic and sedative effects, myrcene alone does not reduce anxiety, depression, or psychosis, and in high doses may actually cause anxiety. Recent in vitro research indicates that myrcene as well as CBD activate the TRPV1 receptor system involved in pain modulation. Myrcene residues linger after binding to shared receptors and thereby may attenuate the pain-modulating effects of CBD.

Myrcene also affects the permeability of cell membranes and may facilitate the uptake of cannabinoids and terpenes by the lungs and other tissues. These actions in concert may produce the “rush” smokers feel when inhaling a large hit of terpene-rich sinsemilla flowers, concentrates, or extracts. Myrcene may also synergistically influence the actions of THC and thereby produce differing effects than THC alone. Although both anecdotal insights and laboratory research indicate that myrcene may reduce inflammation and enhance pain relief as well as lengthen sleep, there is as yet no clinical evidence linking myrcene at the levels commonly found in sinsemilla with sedative, anti-inflammatory, or pain-relieving analgesic effects in humans.

MYRCENE PATENTS

Myrcene is so prevalent in modern sinsemilla that its absence has become an important point of difference in cannabis breeding, plant variety protection, and intellectual property rights claims. The broad-ranging utility patents filed by Mark Lewis and assigned to Biotech Institute focus on processes related to breeding Type 2 varieties with CBD levels roughly equal to or exceeding those of THC, and Type 4 varieties with limited minor cannabinoid content. Eight patents describe plants not having myrcene as the dominant terpene, with six of those producing either limonene, terpinolene, linalool, or caryophyllene as the designated dominant terpene.

However, applications filed by the same group for both patents and plant breeder’s rights on individual clonal cultivars reflect more diverse interests. These include three Type 1 high-THC cultivars (one is myrcene-dominant, another has myrcene as the third terpene, and myrcene ranks lowest in the third) suitable for adult-use markets; four Type 2 cultivars with CBD levels exceeding those of THC (one is myrcene dominant) suitable for medicinal markets; and two Type 3 high-CBD cultivars with THC levels around the Farm Bill approved maximum of 0.3% THC, making them suitable for CBD isolate production.

MYRCENE’S FUTURE

Myrcene is here to stay. Breeders may favor other terpenes, but myrcene forms the heart and soul of Cannabis and will always flavor our human-cannabis relationships. Presently, myrcene receives more attention from researchers than many other terpenes and its medicinal values are increasingly verified. However, we have much to learn about the effects of terpenes at the levels present in sinsemilla flowers and products, especially in their edible and vaporized forms. Myrcene’s dominance throughout commercial sinsemilla attests to an immediate need to promote genetic, phenotypic, and chemotypic diversity in Cannabis cultivars. Variety is



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