Cannabinoids Enriched Extracts from Industrial Hemp Residues

Abstract

Obtaining phytocannabinoids, associated with various medicinal and therapeutic properties with no reported side effects, is one of the hot topics. The phychotropic Δ⁹-tetrahydrocannabinol (THC) is less than 0.2 % in industrial cultivars therefore can be grown legally in many EU countries. Harvesting and processing of hemp for fiber or seeds generates large amount of wastes containing substantial amounts of bioactives such as cannabidiol (CBD) which are the primary cannabinoids along with cannabidiolic acid (CBDA), cannabinol (CBN), cannabigerol (CBG), and cannabichromene (CBC).
The aim of this work was to optimize the extraction of cannabinoids from industrial hemp threshing residue using supercritical carbon dioxide extraction in pilot scales. The effects of extraction pressure and temperature on the extraction yield were evaluated. Three ground and pelleted samples of the same type but with different harvesting time were also compared. After derivatization of the samples the cannabinoids and the minor THCs were quantified by GC-MS. The extraction yields were between 0.2 – 6.59 g/100 g dry mass depending on the source of hemp residue and on the process parameters of the extraction process. By increasing the pressure of extraction (in the range of 25-45 MPa at 45 °C) the extraction yields increased, meanwhile the yields of cannabinoids showed no significant increase. The volatile compounds were successfully separated from the cannabinoids with fractionated separation. From hemp threshing residues essential oil free extracts with high content of cannabinoids were obtained at 35 MPa extraction pressure and 45 °C temperature setting the first separator at 8 MPa and 40 °C.