High added-value compounds from Cannabis threshing residues

Industrial hemp cultivation in Europe is dual-purpose, with stalks providing fibers and hurds, and seeds being used for food, feed and pharmaceutical applications. Economic sustainability of hemp cultivation should encompass the possibility of recovering non-narcotic secondary metabolites from hemp by-products (leaves, leaflets and bracts) originating from seed harvest and seed cleaning procedures. Surprisingly, no information is currently available on the contents of high added value bioactive compounds (CBD, CBG, cannflavin A, Δ9-THC) in industrial hemp inflorescence and threshing residues. This observation provided a rationale for investigating the issue on three monoecious varieties grown in Northern Italy. The concentration of target compounds was monitored from full-flowering until plant senescence by LC–MS/MS analysis of methanolic extracts of the plant biomass. The anti-inflammatory prenylated flavonoid cannflavin A was present in all varieties at levels mainly affected by genotype and air temperature. Conversely, the concentration of CBD, currently the clinically most promising non-narcotic cannabinoid, correlated to the overall extent and distribution of precipitation during growing cycle. Our findings suggest that postponing harvest after seed maturity increases the CBD contents and increase the CBD/Δ9-THC ratio in harvest threshing.