Biorefining of industrial hemp (Cannabis sativa L.) threshing residues into cannabinoid and antioxidant fractions by supercritical carbon dioxide, pressurized liquid and enzyme-assisted extractions

C. sativa threshing residues were biorefined by consecutive supercritical carbon dioxide (SFE-CO2) pressurised liquid (PLE) and enzyme-assisted extractions (EAE). SFE-CO2 at optimised parameters yielded 8.3 g/100 g of lipophilic fraction containing 0.2 and 2.2 g of cannabidiol and cannabidiolic acid per 100 g of threshing residues, respectively. The recovery of cannabinoids from plant material was >93%. PLE gave 4.3 and 18.9 g/100 g of flavonoid-containing polar extracts, while EAE added 20.2% (w/w) of water-soluble constituents and increased the release of mono- and disaccharides by up to 94%. Antioxidant capacity of non-polar and polar fractions was in the range of 1.3-23.5 mg gallic acid equivalents/g DW and 0.6-205.2 mg Trolox equivalents/g DW, with the highest activities of PLE-EtOH/H2O extract. The combined SFE-CO2, PLE and EAE reduced antioxidant capacity of starting plant material by 90-99%, showing that suggested multistep fractionation procedure is efficient in the recovery of a major part of the antioxidatively active constituents from hemp threshing residues.