A more efficient approach to the large-scale purification of cannabidiol
The CPC 250 with a PLC 2250 Purification System; an analytical HPLC platform is used to analyse the CPC extracts
Cannabidiol (CBD), a component of cannabis, has been receiving increased attention for its medicinal value. In fact, 23 states in the US have already recognised the medical benefits of CBD.1 The US Food and Drug Administration (FDA) considers CBD (Figure 1) to be an “investigational drug,” and it has been made available to treat epilepsy in special cases.2
Figure 1: Chemical structure of cannabidiol
However, the purity of commercial CBD products cannot be guaranteed, as there are no established regulatory standards for its production.3 As the compound becomes more mainstream, it will be required by FDA to be free from contaminants — such as tetrahydrocannabinol (THC) — that can diminish the product’s safety and efficacy.
Traditional methods for purifying compounds from natural products, such as high performance liquid chromatography (HPLC) and flash chromatography, can be used to purify small amounts of CBD. However, these methods are too expensive and labour-intensive to scale-up for commercial manufacturers who need to produce large amounts of purified product. For one, because natural products contain thousands of compounds, they contaminate chromatography columns very quickly. As a result, the silica, which is expensive, must be replaced every few weeks or months, making the purification process cost-prohibitive.
Additionally, traditional chromatography involves too much hands-on time. To extract CBD from cannabis using chromatography, the crude cannabis oil must first undergo a labour-intensive pretreatment process, which decreases the production rate.4
Although it’s not a new technology, one method that is well suited for the large-scale production of CBD and other cannabis extracts is centrifugal partition chromatography (CPC). Compared with traditional purification methods, CPC is faster, uses fewer materials and produces a larger quantity of pure compound in a shorter timeframe, rendering it a highly scalable technique to produce pure CBD for therapeutics.
CPC works by the same principles as traditional chromatography, yet it is a simpler process. Instead of costly silica, the stationary phase in a CPC cell is composed of an inexpensive liquid commonly used in the laboratory, such as water or alcohol. Also, crude cannabis oil does not need to be pretreated; rather, it simply needs to be diluted into the eluent, which can then be injected directly into the centrifuge, saving time and material.
During a CPC run, the stationary phase is held in place by centrifugal force, while the cannabis oil is pushed through a series of cells. As the cannabis oil passes through each cell, different compounds diffuse into the stationary phase according to their affinity to it, ultimately separating into different cells along the way (Figure 2).
Figure 2: The CPC process. The mobile phase (yellow) is pushed through the stationary phase (blue) across a series of cells; the solutes (A, B, and C) in the mobile phase are left behind in separate cells according to their respective affinities to the stationary phase
As no silica is present, natural products such as cannabis do not leave behind residues that cause cross-contamination, so CPC cells can simply be rinsed and reused. The reusability significantly adds to the cost-effectiveness of the method.
CPC yields large quantities of nearly pure CBD in a very short period of time. In one demonstration, Gilson researchers injected 5 g of crude cannabis oil into their CPC 250 Pro System (Gilson, Inc., Middleton, WI, USA), and obtained 600 mg of >90% pure CBD and 150 mg of >90% pure THC in 10 minutes.5
In a demonstration of CPC’s production rate, Gilson’s CPC 10L PRO System was able to process 18 kg of crude cannabis oil in 8 hours, presumably generating kilograms of CBD and THC. As CPC uses a liquid stationary phase, manufacturers can use 3–5 times less solvent to elute the target compound than they use with traditional chromatography.6
CPC can purify multiple cannabis components besides CBD, including THC, tetrahydrocannabinolic acid, cannabidiolic acid and terpenoid. It can also purify other natural products, such as piperine from pepper.7 Production-scale CPC can help pharmaceutical companies to meet good manufacturing practice standards. It is important to note that CPC is not an analytical technique, which means it requires an analytical HPLC to produce chromatograms to validate the CPC process.
CPC may be unfamiliar to most manufacturers; they might have to spend additional time learning how to optimise the technology for maximum production. Gilson Purification’s Applications Laboratory, based in Vannes, France, is equipped to assist manufacturers with incorporating CPC into their CBD production workflows. The Applications Lab contains a training centre for preparative chromatography for CPC, which helps to shorten the learning curve. Their team of experts is also dedicated to optimising the CPC process for large-scale CBD production and creating turnkey solutions for the industry.
As the demand for CBD increases, so will the need for a scalable purification method. CPC is inexpensive and efficient, making it the ideal tool to produce large quantities of pure CBD for pharmaceutical manufacturing.