What gives marijuana its signature scent?

Sacramento cannabis enthusiasts have yet another thing to be snobs about in 2012: terpenes, the building blocks that make up the unique smell of cannabis, which are beginning to waft into the mainstream.

Drug companies are researching the therapeutic properties of these simple organic molecules, and at least two California medical-cannabis labs have begun testing for their presence in dispensary weed.

According to Donald Land, a UC Davis chemistry professor who cofounded Halent Laboratories, which tests for terpenes and conducts occasional smelling classes, “Terpenes are a set of relatively simple organic molecules that are present in all living organisms.” He noted that most of the flavors and aromas of plants comes from terpenes.

“The name terpene is derived from the main ingredient in a certain type of pine pitch called turpentine,” Land explained. “That piney smell that comes along with turpentine comes from terpenes. There are lots of others.”

Herbalists have recognized the power of terpenes for decades. “Cannabis and other plants share a lot of the same terpenes, so terpenes have been legal for many decades,” Land said. “There’s been quite a bit of research on them in the U.S. and abroad, including many well-documented medicinal effects.”

Rick Pfrommer, manager at Harborside Health Center in Oakland, said that as head buyer for the popular dispensary, he has smelled countless numbers of bags and glass jars full of the sticky ick, and that a lot of the odors he detects aren’t actually coming from the weed.

“You can smell everything from bat guano to heavy salt-hydroponic fertilizers,” Pfrommer said during an interview inside Harborside’s buyer’s room. The space is dominated by an examination counter, shelves of pot-strain reference books and expensive computers. Pfrommer has been selling ganja for about 25 years.

Pfrommer insists that if one boasts an acute sense of smell, you can smell chlorophyll in a bud that hasn’t been cured well, and even molds. “Once you’ve smelled multiple thousands of samples of cannabis,” he explained, “when something is off, it’s apparent that it’s off, like, as soon as you crack the bag open.”

Like a wine sommelier or a buyer for a boutique coffee roaster, Pfrommer smells each potential new addition to Harborside’s menu using a specific ritual. First, he pops open a glass jar of coffee beans and takes a big sniff. Like ginger before sushi, coffee beans reset the palate, he said. Then he takes a big whiff from a sample cannabis bag, fishes out a single nug, cracks it open, and inhales deeply.

“All you really want to smell is the terpenes,” he said.

According to a literature review by the medical-cannabis journal O’Shaughnessy’s: “Limonene (also found in lemon) is an antidepressant and immune-stimulant in humans; alpha-pinene (also found in pine needles) is an anti-inflammatory, a bronchodilator, and a wide-spectrum antibiotic; nerolidol (also found in oranges) is a sedative; linalool (also found in lavender) has an anti-anxiety effect; and myrcene (also found in hops) is a sedative, a muscle relaxant, a sleep aid, and an anti-inflammatory.”

Trainers teach drug dogs to hunt for beta-caryophyllene, a terpene in cannabis that also is an anti-inflammatory. Terpenes are also the chemical precursors to the euphoric ingredient in pot, tetrahydrocannabinol, or THC, making them a proxy for potency.

Researchers like Ethan Russo, senior medical director at GW Pharmaceuticals, believe that terpenes contribute to the “entourage effect” that lies at the core of medical cannabis’s efficacy in treating nausea, inflammation, chronic pain and more. GW Pharmaceuticals has started growing terpene-only pot—sans THC—to better investigate the effects of terpenes, O’Shaughnessy’s reported.

And, unlike the THC pill Marinol, new prescription throat spray Sativex contains THC, its therapeutic peer CBD, and terpenes.

Terpenes also enable pot snobs to make outlandish yet credible claims that they smell chocolate, mango, diesel or lavender in their bag. The five to 10 main terpenes in cannabis have about 25 more rare peers, but cannabis has been found to contain more than 200 different types of them. The combinations are infinite.

Cannabis lab data from Halent and The Werc Shop near Los Angeles is helping to elevate breeding to a science. It’s also giving patients a first-ever ingredients list for that dubious doobie, said Jeffrey Rabe, director of The Werc Shop.

Pfrommer envisions legal OG Kush deodorizers or Agent Orange floor cleaners. “I think, along with CBD, terpenes are one of the two most exciting things going on in cannabis,” Pfrommer said. “We’re just scratching the surface now.”

And sniffing.