Menthol-based hydrophobic deep eutectic solvents: Towards greener and efficient extraction of phytocannabinoids

As the demand for medical cannabis preparations increases, so does the use of the common organic solvents that are used in the extraction and quantification of phytocannabinoids. Since common organic solvents are typically hazardous to the environment and to human health, it is vital to identify safer, greener, and more efficient alternatives. The aim of the present research was to develop a series of hydrophobic deep eutectic solvents (DESs) based on terpenes and natural organic acids and to establish whether these might be potential substitutes for the extraction of phytocannabinoids (tetrahydrocannabinol, cannabidiol, and their carboxylated homologues) from raw cannabis plant material. Data were obtained using capillary electrophoresis with diode array detection (DAD). Initial screening showed that the DES composed of a menthol: acetic acid (1:1 M ratio) mixture showed the greatest extraction efficiency (of all the DESs that were tested), with yields ranging from 118.6% to 132.6% (compared to a methanol: chloroform mixture). In conclusion, menthol: acetic acid DES extraction is efficient, as well as non-toxic and biodegradable. As such it has applications within the pharmaceutical industry and represents a greener alternative organic solvent for the extraction of phytocannabinoids.