Thermo-chemical conversion of cannabis biomass and extraction by pressurized liquid extraction for the isolation of cannabidiol

Abstract Cannabis plants produce acidic cannabinoids, however the neutral form is required to effectively bind to the human cannabinoid receptor. This research aimed to develop and validate methodology for thermo-chemical conversion of acidic cannabinoids during pressurized liquid extraction for the isolation of cannabidiol. Cannabinoid decarboxylation is typically performed by heating plant material or extract, however cannabinoids are thermolabile and can readily degrade or convert to undesired metabolites. Consequently, decarboxylation during the extraction process would minimize additional steps and potential for degradation and metabolite formation thereby proving beneficial in the isolation of neutral cannabinoids. A thermo-chemical conversion process was established to convert acidic cannabinoids to their neutral forms. Subsequent extraction with ethanol yielded a cannabidiol extract of 75.8 % purity. Purification with flash chromatography resulted in cannabidiol rich fractions being collected for liquid-liquid extraction and crystallization. The end product was 91.8 % pure. The loss over the extraction and purification process was analyzed and found to be 22 %, which can be reduced by reprocessing select fractions. The optimized pressurized liquid extraction method using water for thermo-chemical conversion of acidic cannabinoids prior to an ethanol extraction step is proposed. The extraction process combined with purification by flash chromatography and liquid-liquid extraction yields cannabidiol crystals of greater than 90 % purity.