A new prototype reactor for the fast microwave-assisted decarboxylation and extraction of cannabinoids in olive oil from Cannabis inflorescences

Abstract

Several different Cannabis-based pharmaceutical preparations have been approved for medical treatments. Standardization to ensure specified phytocannabinoid contents and to maintain the integrity of the product is therefore required. Olive oil is clearly a safe and edible solvent suitable for the galenic preparation of ready-to-use Cannabis extracts. Pharmacists can use several non-standard procedures for this purpose, most of which involve the heat treatment of the plant matrix (i.e. the female inflorescences) for 2 h. In order to allow the “neutral” and more biologically active forms of the major phytocannabinoids to be extracted, prior thermal treatment of the plant matrix is desirable. This work investigates a new prototype microwave (MW) reactor (Ethos Lean) specifically designed for the decarboxylation of the acidic cannabinoids in Cannabis inflorescences and their subsequent extraction into oil. Both of the steps to produce the oily extract were carried out in the Ethos Lean's cavity with special accessories; a rotating drum for the decarboxylation process and a glass reactor with a stirrer for the extraction step. The variables considered in the process optimization were time and temperature, according to which the instrument automatically calibrated the power output. In collaboration with a hospital pharmacy, the efficiency of the device has been evaluated by comparing the results obtained with those of exhaustive decarboxylation in a conventional oven and ethanol extraction. A comparison was also made with conventional procedures in olive oil. Thanks to the rotating drum, which is sensitive to dielectric heating, the complete and homogeneous decarboxylation of phytocannabinoids was rapidly achieved (30 min, 120 °C), even with discrete quantities of inflorescences (150 g) and without releasing the characteristic intense odor into the laboratory. The exhaustiveness (100% yields of both CBD and THC) of MW-assisted extraction process in olive oil was achieved with 30 min irradiation at 90 °C. Furthermore, the possible decarboxylation occurring during MW-assisted extraction in oil and the effect of cooling time on the final yields have also been evaluated.