Extraction and purification of cannabinoids for the Medical Cannabis industry

Before developing the methods to extract cannabinoids from cannabis plant material, there are a number of steps that will need to be understood and implemented. Plant material with the desired chemical characteristics (e.g. the most appropriate cannabinoid profile) will need to be chosen. This may involve the selective breeding of premium plants or the purchase of PBR rights to grow a particular plant. Once this is completed, the plants will need to be grown under optimal conditions (e.g. fertiliser, day length, etc.) for the production of the desired chemical profile.

Once the plants are mature, they will need to be harvested and stored them under ideal conditions (e.g. trimmed to clean buds, dried to remove water, stored cool and in the dark, etc.). Only then can the extraction of the plant material be commenced.

It is important that the specifications of the final extract are understood before processing begins. These specifications can range from a very crude extract containing all of the available terpenes, flavonoids and cannabinoids (along with the pigments and plant waxes) used for the Entourage effect to a high purity cannabinoid product.

Ethanol extraction

  • Extract bud material with 100% ethanol (optimise volume, time and temperature).
  • Concentrate the extract.
  • Winterise to remove plant lipids
  • Filter to remove any chlorophyll
  • Decarboxylate to “activate” cannabinoids

CO2 extraction

  • Extract the bud material with CO2 ± ethanol (optimise for pressure, temperature, [ethanol], etc.).
  • Winterise to remove plant lipids
  • Filter to remove any chlorophyll
  • Decarboxylate to “activate” cannabinoids
  • Analyse for yield and purity.

Propane/Butane extraction

  • Extract the bud material with propane or butane.
  • Remove any hydrocarbons
  • Winterise to remove plant lipids
  • Filter to remove any chlorophyll
  • Decarboxylate to “activate” cannabinoids

There are a number of other processes that have been used to extract and/or concentrate active material from cannabis plant material (e.g. trichromes, rosin, kief, hash, olive oil, etc.), but these are not generally used commercially. Each extraction process has advantages and disadvantages (which will be discussed in a subsequent article), and these need to be considered before an extraction process is chosen and implemented.

If the primary extract produced above does not meet the specifications required by the customer, further purification and fractionation of the extract may be necessary. These additional steps may include Fractional Distillation, Centrifugal Partition Chromatography (CPC), Preparative HPLC, Flash Chromatography and Crystallisation.