Mechanism and kinetics of CBDA decarboxylation into CBD in hemp

Cannabidiol (CBD) is a pharmacologically active ingredient for use in medical, cosmetic, and food products. CBD forms from cannabidiolic acid (CBDA) with the process of decarboxylation by heating cannabis ( Cannabis sativa L.) material. During the production of CBD-rich material, decarboxylation should be performed in precise conditions regarding temperature and time. The experiments were performed by heating hemp samples at 100, 110, 120, 130, and 140 °C for 180 min. Materials were sampled every 20 min and cannabinoid content was analyzed using HPLC, followed by calculation of kinetic parameters. Experimental results showed an exponential reduction of CBDA in the samples during heating. CBD simultaneously increased, and after a specific point, CBD started degrading. The optimal conditions were 140 °C for 30 min. At the level of molecular orbitals, reaction steps, and reaction coordinates, along with the corresponding changes in molecular energy, the molecular mechanism of CBDA decarboxylation and CBD formation was described. Computational analysis has confirmed that the mechanism of CBDA decarboxylation is a direct beta-keto acid pathway. The course of CBDA decarboxylation depends on the time, temperature, and chemical composition of the sample.