Centrifugal partition chromatography’s new use: medical marijuana | Nature

By September 14, 2018Cannabis

The U.S. FDA recently approved the first drug comprised of an active ingredient in cannabis, or marijuana. As the hunt for new cannabis compounds heats up, so will the need for new tools with which to isolate them.Credit: Stefan Wermuth/Bloomberg Creative Photos/Getty Images

As of spring 2018, more than 20 countries, as well as 29 U.S. states, had legalized the sale of cannabis for medicinal or recreational use, spawning a multibillion-dollar industry that reaches from Alaska to Zimbabwe. The ‘Green Rush’ has launched a new generation of entrepreneurs and inspired a stream of cannabis products, from the plant itself, to artisanal foods, marijuana-infused body lotions, and discreet vaporizer pens.

Investment funds are also pouring in for cannabis-derived medicines — with the first such therapy poised to hit in the US market this year after an advisory committee to the country’s Food and Drug Administration voted unanimously in April to approve a cannabis-based product called Epidiolex for treating childhood epilepsy.

Pharmaceutical interest is focused on the plant’s many compounds, including its terpenoids, and its namesake cannabinoids — the group of related compounds that include the psychoactive agent tetrahydrocannabinol (THC) and the medicinal substance cannabidiol (CBD) — any number of which could offer treatment for or pain relief from a range of debilitating diseases.

Although these molecules can be synthesized in the laboratory, many companies prefer to source the compounds from plant extracts, sometimes purifying them further by distillation. Even using this method, however, the result “is still a mixture of whatever cannabinoids are coming from a particular marijuana strain, which is a highly variable thing,” says Brian Reid, chief scientific officer of ebbu, a Colorado company that specializes in cannabis purification.

And while unpredictable mixtures might satisfy the consumer market, where most people just want the buzz of THC, or the presumed health benefits of CBD, they are not ideal for therapeutics. Doctors want to know what they’re prescribing and patients want the confidence that the dose they took yesterday will be the same as the one they have today.

“It will definitely be an advantage to have cannabis-based medications with clearly defined and constant contents of cannabinoids,” says Kirsten Müller-Vahl, a neurologist and psychiatrist at Hannover Medical School in Germany.

As demand for cannabis-based therapeutics increases, so will the pressure on companies and scientists to find more exact ways to isolate and purify compounds.

Precision extracts

Because extracts are the primary source of cannabis compounds, most companies have focused on improving those sources rather than seeking new ones. For example, GW Pharmaceuticals, the company behind Epidiolex and the biggest firm developing cannabis-based medicines, develops its extracts from a stock of identical cannabis clones and a common carbon dioxide (CO2)–based extraction method. Depending on what chemovar the company starts with, the resulting extract is either 60% THC or 60% CBD, with other cannabinoids making up another 6% or so, according to GW’s patent filings. The company then uses one or both of these extracts to produce its Sativex drug for multiple sclerosis (approved in Europe, Canada, Australia and elsewhere) or the newer Epidiolex drug for epilepsy.

Diagram showing the chemical constituents of cannabis
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