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The Same Compounds Behind Marijuana's Distinctive Stinky Smells Give Clues About the Kinds of High You'll Experience

The secrets behind marijuana’s bouquet are in the "terpenes."
 
 
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The first thing you notice upon entering a well-stocked medical marijuana dispensary is the many varieties of cannabis on display – dozens of glass jars filled with glistening, manicured bud. Everyone has their favorites: OG Kush, Headband, Sour Diesel, Flo, Lemon Thai, Super Silver Haze ... Some strains are energizing, some are sedating; some are better for pain, others for inspiration.

A couple hits of high-THC herb, by whatever name it’s called, will get you good and stoned. But it’s not the amount of delta-9-tetrahydrocannabinol that accounts for the particular properties of each strain. Nor are the minuscule quantities of cannabidiol (CBD) or the hundred or so “minor” cannabinoids a key factor in most strains. With few exceptions, the THC levels are lofty, while the other cannabinoids barely register their presence, according to labs that test samples for growers and dispensaries in states where medical marijuana is legal.

So if THC levels are generally high across the board and the other cannabinoids are present only at trace levels, what makes one strain different from another? And why does each marijuana strain impart a distinct psychoactive effect? There must be something else in the plant that influences the quality of the cannabis high.

David Watson, the master crafter of the foundational hybrid Skunk #1, was among the first to emphasize the importance of aromatic terpenes for their modifying impact on THC. Terpenes, or terpenoids, are the compounds in cannabis that give the plant its unique smell. THC and the other cannabinoids have no odor, so marijuana’s compelling fragrance depends on which terpenes predominate. It’s the combination of terpenoids and THC that endows each strain with a specific psychoactive flavor.

In 1989, Watson and his business partner, Robert Connell Clarke, formed HortaPharm, a legally chartered, Holland-based research company that specializes in botanical science and cannabis therapeutics. Based in Amsterdam, these two American expatriates broke new ground in horticultural pharmacology as they crossed and recrossed thousands of cannabis varietals, discarding most along the way while selecting a relatively small number for further development.

How did they decide which plants made the first cut? “We smelled them,” Watson explains.

He had long suspected that the terpenes present in cannabis resin enhance the potency of THC. Ten years after launching HortaPharm, Watson tested his hypothesis in an experiment that compared the subjective effects of 100 percent THC to lesser amounts in terpene-infused cannabis resin. The consensus among Watson and several associates: Terpene-infused resin with 50 percent THC was more potent by dry weight than an equivalent amount of pure THC.

Typically, terpenes are volatile molecules that evaporate easily and readily announce themselves to the nose. Therein lies the basis of aromatherapy, a popular alternative-healing modality. Like their odorless cannabinoid cousins, terpenes are oily compounds secreted in the marijuana plant’s glandular trichomes. Terpenes and THC share a biochemical precursor, geranyl pyrophosphate, which develops into the cannabinoids and terpenoids that saturate the plant’s flower tops.

But unlike THC and the other plant cannabinoids that exist nowhere else but in marijuana, terpenes are ubiquitous throughout the natural world. Produced by countless plant species, terpenes are prevalent in fruits, vegetables, herbs, spices, and other botanicals. Terpenes are also common ingredients in the human diet and have generally been recognized as safe to consume by the US Food and Drug Administration.

Scientists have identified and characterized the molecular structure of some 20,000 terpenes, which compose the largest category of plant chemicals. These can be further broken down into mono-terpenes, diterpenes and sesquiterpenes, depending on the number of repeating units of a five-carbon molecule called isoprene, the structural hallmark of all terpenoid compounds.

 
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