Development of a dispersive solid-liquid microextraction method using natural eutectic solvents for a greener extraction of phytochemicals from fiber-type Cannabis sp

The use of plant materials as natural resources has become fundamental for several applications, in perspective of a sustainable growth. Cannabis sp. crop perfectly fits this purpose, thanks to its rich phytocomplex, that can be exploited in pharmaceutical and cosmetic industry. At the same time, the increasing demand for innovative technologies, energy saving and greener solvents makes necessary the development of new extraction methods to obtain the metabolites of interest. In this study, a dispersive solid-liquid microextraction (DSLME) method, using natural eutectic solvents (ESs), was first optimized and validated for the extraction of the non-volatile fraction of the aerial parts of hemp collected before flowering. The DSLME was directly carried out on the freeze-dried powder of the plant, without the need of a pre-extraction with harmful organic solvents. The optimized method is fast and easy to perform compared to conventional procedures, and only requires 100 µL of ES and 2 mL of water. The ES easily formed the dispersion in water after 30 s of vortex, and no dispersive solvent was added. After 10 min of sonication, the enriched phase was simply recollected after centrifugation and solubilized in 500 µL of methanol/water (70:30, v/v) before the injection in the UHPLC-PDA system. Several natural compounds (menthol, linalool, terpinen-4-ol, eugenol, carvacrol, thymol) were combined and the influence of the two components of the ES, on the performance of extraction, was also evaluated. The proposed solvents showed a higher enrichment of cannabinoid compounds compared to the more polar flavonoids, thanks to the hydrophobic features of the proposed ESs.