Fibre hemp inflorescences: From crop-residues to essential oil production

The volatile composition of ten fibre hemp (Cannabis sativa L.) varieties was investigated during two successive growing seasons under temperate climatic conditions in Central Italy. The freshly plant inflorescences were hydrodistilled and the essential oils (EOs) were characterized by GC-MS. In addition, the composition of the aroma emitted spontaneously from the freshly plant inflorescences were analysed by SPME-GC-MS. The EO yields of eight dioecious (Carmagnola, C.S., Red Petiole, Pop 1, Pop 2, Pop 3, Pop 4, Pop 5) and two monoecious (Codimono and Felina 34) cultivars ranged from 0.11 to 0.25% (w/w) and showed a significant production of α-pinene (3-20%), β-pinene (1-8%), E-ocimene (1-10%), myrcene (8-45%) and terpinolene (0.12-22%). The monoterpene composition was useful to distinguish the monoecious cultivars from the dioecious ones. β-Caryophyllene (7-28%), α-humulene (3-12%), and caryophyllene oxide (2-6%) were the main sesquiterpenes. Tetrahydrocannabinol (THC) was present in traces in the EOs of only two dioecious cultivars cultivated in 2005. Cannabinol (CBN) was not detected in the essential oils, while the no-hallucinogenous cannabidiol (CBD) was found as typical volatile constituent in several analysed cultivars. These findings were also confirmed by the headspace GC-MS analysis carried out on the same samples. The analysed EOs obtained from fibre hemp varieties cultivated in Central Italy were characterized by an interesting and specific terpene composition with a legal and safe cannabinoid content. They were obtained from freshly plant inflorescences, which usually represent a waste material from C. sativa L. fibre varieties. The present study strengths the hypothesis to grow hemp as a multi-use crop through a complete utilization of the plant material using inflorescences to produce essential oils as natural flavour and fragrance additives.