Methods of Purifying Cannabinoids from Plant Material (GW Patent)

Outlined in pretty thorough details are the methods for purifying THCA, CBDA, d9-THC, THCV, CBG, and CBC which GW Pharmaceuticals thought worth patenting back in 2005.

Most involve ethanolic extraction of chemovars selected for their expression of specific cannabinoids, followed by filtration and rotary evaporation to give an enriched extract. This enriched extract is then eluted through Sephadex LH20 with 2:1 TCM:DCM, and the relevant fractions are gathered. The solvent is then removed by rotary evaporation, the extract redissolved in MeOH, insoluble filtrate removed, evaporated again and then redissolved in pentane before filtering again, and removing solvent for the final time to give a substantially pure preparation of the desired cannabinoid.

Iā€™m not sure why they chose to opt for SEC, especially when they had the luxury of working with chemovars selected for favourable cannabinoid expression. Scaling this production becomes prohibitively expensive given Sephadex-LH20 is $4000/kg too.

Interesting reading even if only for the theory.

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