Selective recovery of terpenes, polyphenols and cannabinoids from Cannabis sativa L. inflorescences under microwaves

Abstract

In recent years, hemps health and nutritional properties recognition has led to an impressive growth of Cannabis research, industrial processing, and the related market. Moreover, the demand for natural Cannabis-derived compounds (i.e. terpenes, polyphenols, and cannabinoids) is constantly growing. In spite of the strict regulation of some countries, the global market needs suitable technologies for the smart recovery of bioactive Cannabis metabolites. Conventional extraction procedures can show drawbacks, in terms of environmental impact and their high energy consumption. Microwaves (MW), a mature technique for extraction-process intensification, is attracting great amounts of attention in academic-research and industrial-application fields for its technological advantages. This work aims to design a fast and cost-efficient MW-assisted cascade protocol for bioactive Cannabis compounds recovery in a pilot-scale reactor. Microwave-assisted hydrodistillation (MAHD) can provide a volatile hydrodistillate that is rich in monoterpenes, sesquiterpenes, and a small amount of phytocannabinoids. Using non-canonical protocol of hydrodistillation, the definition of “volatile fraction” is generally considered more appropriate than “essential oil”.The health-promoting activity of this combination has been proposed in literature, and can constitute matter of further investigations. The optimized MAHD procedure yielded 0.35 ± 0.02 % w/w of hydrodistillate, while conventional hydrodistillation gave only 0.12 ± 0.01 %, w/w (in relation to dry inflorescence mass). The water resulting in the vessel after MAHD showed a high total polyphenolic content (5.35 ± 0.23 %, w/w). Two flavones known for their beneficial effects to health, namely luteolin-7-O-glucoside and apigenin-7-O-glucoside, were detected and quantified. An attempt to recover phytocannabinoid using the MW-assisted hydrodiffusion and gravity method (MAHG) was also carried out. Cannabinoids (CBD and THC) content was determined in fresh Cannabis and in production streams. During MAHD, phytocannabinoid decarboxylation inside the residual matrix was around 70 % (69.01 ± 0.98 % and 74.32 ± 1.02 % for THC and CBD respectively). Furthermore, the overall content of these metabolites was not affected by the hydrodistillation, preserving the processed plant material for subsequent ethanolic extraction.