O. Aleknavičiūtė, R. Baranauskienė, P. R. Venskutonis
Kaunas University of Technology,
Lithuania
Keywords: Cannabis stiva, suoercritical carbon dioxide fractionation, phytocannabinoids, waxes, essential oils
Summary:
Hemp or industrial (fiber type) hemp is one of the fastest growing plants and was one of the first plants to be spun into usable fiber 10,000 years ago. It belongs to the same Cannabis sativa species, which has been used as a cannabis drug containing high content of the psychoactive component tetrahydrocannabinol (THC). Its content in hemp is remarkably lower (less than 0.2-0.3%), whereas another, non-psychoactive phytocannabinoids such as cannabidiol (CBD) and cannabigerol (CBG) may be present at remarkably higher concentrations; they are biosynthesized in the plant mainly in the form of carboxylic acids. I general, more than 100 phytocannabinoids have been identified until now in various C. sativa cultivars. CBD is one the most abundant compound in the majority of fibre type cannabis breeds with large pharmacological and health beneficial properties. For instance, the following activities have been reported for CBD in the scientific literature: anxiolytic, antipsychotic, antiepileptic, neuroprotective, vasorelaxant, analgesic, anti-ischemic, antiemetic, proliferative/anticancer, intestinal anti-prokinetic, anti-inflammatory, adenosine immunosuppressive, antipsoriatic, antibacterial, antispasmodic, bone-stimulant, antidiabetic. In addition, hemp accumulates essential oil, which is rich in some sesquiterpenes, which are also assigned to phytocannabinoid class of the natural compounds. Due to these effects hemp and its bioactive constituents have attracted significant attention both among the researchers and producers. Phytocannabinoids are usually recovered from hemp leaves and inflorescences with organic solvents (hexane, ethanol, isopropanol) or by supercritical carbon dioxide extraction. The latter method possesses several advantages such as the use of safe, inflammable, food and environment friendly (‘green’) solvent, and producing solvent residues free products. However, all methods also extract other soluble in the applied solvents substances, particularly the waxes, which dilute phytocannabinoids in the products obtained and therefore are not desirable in the extracts. Traditionally, the waxes are removed from hemp extracts obtained by supercritical carbon dioxide by the method, which is called winterization and includes its dilution in the ethanol, freezing at -20 °C and filtration. This study aimed at separating supercritical carbon dioxide extracts into the wax and phytocannabinoid/essential oil-rich fractions. For this purpose, the system with two separators was used. Dried and ground hemp leaves were extracted at 450 MPa pressure and 45 °C temperature, the pressure in the 1st separator was reduced to 7 MPa, while its temperature was cooled from 0 °C to -30 °C. Pure carbon dioxide and its mixture with 5% co-solvent ethanol were used in the experiments. Two fractions were obtained at the all parameters applied, however, separation of hemp extract was rather ineffective in case of using pure carbon dioxide. Application of the co-solvent ethanol remarkably increased separation effectiveness; for instance, the fraction precipitated in the 1st separator at -10 °C consistent mainly of waxes, while phytocannabinoids and essential oil were collected in the 2nd separator. Depending on the separation parameters applied the enrichment factor for hemp bioactive compounds was approx. 3-10. It may be concluded that effective procedure was developed for the recovery and pre-purification of hemp bioactive constituents using 1-step process.