Wake Up and Smell the Terpenes! How Cannabis Works

The chemical structure of tetrahyrdocannabinol (THC) was determined in 1964 by Raphael Mechoulam and Yechiel Gaoni. For more than three decades thereafter, its blatant psychoactivity induced scientists to define THC as the active ingredient in the plant.
Experienced marijuana smokers who tried the drug Marinol (pure, synthetic THC) when it became prescribable in the mid-1980s, reported that the effects were noticeably dissimilar. But it wasn’t until the late 1990s that the research establishment acknowledged that another compound, cannabidiol (CBD), was exerting significant effects, too.
In 1999 a British start-up, G.W. Pharmaceuticals, began clinical trials of a plant extract containing equal amounts of THC and CBD. Multiple Sclerosis patients found the combination more effective in reducing pain and spasticity than a THC extract, and less psychoactive. The THC-CBD combo, “Sativex,” has now been approved for use by MS patients in England, Canada, New Zealand, and a growing list of European countries.
Several of the so-called “minor cannabinoids” —notably tetrahydrocannabavarin (THCV), cannabigerol (CBG) and cannabichromene (CBC)— also show therapeutic promise, and plants with high levels of each have been grown out in G.W.’s glasshouses for research purposes.
Now scientists are formally acknowledging something else that Cannabis consumers have long taken for granted: aroma is associated with effect.
Plant cannabinoids —21-carbon molecules found only in Cannabis— are odorless. It’s the terpenoids —components of the plant’s “essential oils”— that create the fragrance. Terpenoids contain repeating units of a 5-carbon molecule called isoprene, and are prevalent in smelly herbs such as mints and sage, citrus peel, some flowers, aromatic barks and woods. The aroma of a given plant depends on which terpenoids predominate. They tend to be volatile molecules that readily evaporate, and they’re very potent —all it takes is a few reaching the nose to announce their presence. The cannabinoid content of a trichome might be 10 times heavier than the terpenoid content.
Evidence that “phytocannabinoid-terpenoid interactions” enhance the therapeutic effects of cannabis was presented by Ethan Russo, MD, at a conference in Israel last fall and is about to be published in the British Journal of Pharmacology. Russo, a neurologist and ethnobotanist,, is senior medical adviser at G.W. Pharmaceuticals.
Terpenoids and cannabinoids are both secreted inside the Cannabis plant’s glandular trichomes and they have a parent compound in common (geranyl pyrophosphate). More than 100 terpenoids have been identified in Cannabis. The most common and most studied include limonene, myrcene, alpha-pinene, linalool, beta-caryophyllene, caryophyllene oxide, nerolidol and phytol. Anecdotal evidence suggests that alpha-pinene is alerting, limonene is “sunshine-y,” and beta-myrcene is sedating...

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Fred Gardner @'Counterpunch'