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What Can We Learn from Terpene Profiles: In Discussion with Dr Keith Allen

By Leo Bear-McGuinness
Published: Sep 24, 2018   
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“The important thing to remember about terpenes is that this stuff did not evolve to get us high,” explains Dr. Keith Allen, Director of Bioinformatics at Steep Hill laboratories. Allen’s work centers on the chemical and genomic profiles of plant materials, and how these data can better inform us about cannabis cultivation. His efforts have helped Steep Hill in becoming one of the most accurate labs in California for profiling cannabis cultivars.

Allen will feature as a Keynote Speaker in Analytical Cannabis’ online symposium, The Science of Cannabis 2018, on September 27, 2018. In anticipation of the event, Analytical Cannabis caught up with the director to discuss his expertise on one of the cannabis industry’s most talked about compound groups: terpenes.

All-natural terpenes

While initially understood to provide cannabis, and many other plants, with their distinctive odors and flavors, terpenes have since been hailed as the plant’s new wonder compounds. Research has shown these chemicals can reduce the negative effects of cancer, malaria, and inflammation, all while playing a role the venerated and therapeutic ‘entourage effect’ when consumed with cannabinoids. But despite all this hype, many users still couldn’t tell you what a terpene really is.

“Terpenes are a mechanism that a plant uses to communicate with its environment,” says Allen. “So that’s attracting either microbes or insects, things that it likes, or repelling things that it doesn’t like.”

Terpenes are a large and broad group of hydrocarbons produced by a variety of plants, particularly conifers, that act as chemical signals to insects and other animals. For example, the potent insecticide group pyrethrins are produced by Chrysanthemum flowers and target the nervous systems of predatory insects. Terpenes have therefore been used as natural pesticides for thousands of years. Aside from affecting nervous tissue, terpenes can also disrupt reproduction and muscle functions, inhibit ion transport, block animal hormones and deter feeding by predators.

So, on the surface at least, they’re not the kind of compound one would expect to find in popular cannabis products. Fortunately, these insecticidal properties are tailored to the plants’ six-legged pests. Compared to insects, mammals generally have a lower nerve sensitivity, greater body size, and more efficient hepatic metabolisms, and so they are– to the great relief of cannabis users - impervious to many of terpenes’ negative effects.

Terpene precursors and shelf-lives

“The diversity of terpene molecules is a lot of what makes the plant so interesting and probably a big component of what makes the plant so effective in the recreational and medical sense,” says Allen.

While it’s hard to pin down just how many different terpene types are present in cannabis – “the number 140 goes around a lot,” adds Allen – the chemical profiles of terpenes can teach cannabis growers a lot about what constitutes a valuable cultivar.

To begin with, all monoterpenes come from the precursor molecule geranyl diphosphate.

“It’s a brilliant molecule,” says Allen. “It’s designed like the ultimate toolbox – you can make this huge number of different molecules out of it once you pop off this diphosphate group.” A pivotal molecule for terpene synthesis, it’s crucial that cannabis analysts like Allen understand as much as they can about geranyl diphosphate in order to manage the production of its valuable (and not so valuable) secondary molecules effectively.

Plus, a better understanding of terpene molecules means a better understanding of their potency and the point at which they become ineffective.

As Allen explains, “Unlike the cannabinoids, the terpenes are volatile - they go away. Fresh bud is a very different thing than stuff that’s sitting in an open jar. And this complicates our terpene profiles as we’ve got this added variable of time”.

What terpene genomics can teach the cannabis Industry

So, as the cannabis industry looks forward to a new wave of craft and medicinal breeding, it stands at a pivotal moment when it comes to terpenes. In the coming years, it will be experts like Allen that will be sought after by companies to determine which types of terpenes they should be producing in their cannabis.

To get the most out of these popular compounds, it’s vital that experts are heard.

“In terms of lessons for breeders, the future of cannabis is going to be very precisely dialed in strains that have very well-defined oil profiles,” explains Allen. “There are a lot of these different terpene synthases to work with, but there are going to be limits to what you can breed.”

At Steep Hill, Allen has combined extensive terpene profiling data with modern genomic approaches to identify a list of genes responsible for producing the large range of terpenes found in cannabis plants. With this knowledge, his team at Steep Hill can map cannabis genes to different terpene oil profiles. The hope is that this database will act as a guide for breeding cultivars with specific terpene properties.

“We want to develop a marker that will tell you, ‘you’ve got an active or dead terpene synthase’. And that’s going to be a very useful thing for breeders to know about,” he clarifies. “Ultimately, that’s what this is about: enabling this very targeted breeding.”

Dr. Keith Allen will be the Keynote Speaker at Analytical Cannabis’ online symposium, The Science of Cannabis, on September 27 2018. You can register to join the symposium here.


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