A difference in terpene contents in the inflorescence according to their position along the stem was noticed. A loss of terpenes and oxidative reactions of sesquiterpenes are induced by the process of drying, forming caryophyllene oxide and humulene epoxide II from caryophyllene and humulene, respectively . Interestingly, two terpenes have also been isolated from an hexane fraction of cannabis roots . Apart from mono- and sesquiterpenes present in the EO, triterpenes have also been recovered from cannabis roots, stem and leaves. The highest content of triterpenoids was found in roots , where friedelin is the major compound identified at a content up to 0.135 w% . Various other triterpenoids including epifriedelin and β-amyrin have also been detected in smaller amounts . Friedelin have shown various biological activities including antiulcer, antidiabetic and cytotoxic effects while β-amyrin have been associated with anti-microbial, anti-fungal properties and a potential anti-inflammatory activity .
To our knowledge, no biological activities have been reported for epifriedelin. Most studies reported here involve hydrodistillation for the extraction of terpenes from C. sativa. This is one of the traditional methods for the recovery of EO from plant biomass. Some authors used CSE while others explored innovative methods, in some cases attempting to intensify or partition the extraction. As mentioned above, biomass conditioning has a significant effect on the EO yield and composition. Drying and storing the plant lead to a significant decrease in the percentage of EO, as observed in several studies . The two processes cause the evaporation of high vapor pressure components. In particular, EO composition is characterized by a higher loss of the most volatile components, monoterpenes, and therefore an increased percentage of sesquiterpenes .A further decrease in the EO yield occurs when the drying temperature is increased.Hydrodistillation and steam distillation are among the most popular methods used to extract EO from plant sources. These methods were developed to lower the boiling point molecules using the water vapor pressure.
The water steam penetrates the biomass and dissolves the volatile compounds. Solvent and solutes are then condensed that causes their separation, the upper phase of the liquid being the essential oil. The slight difference in the methods is that the steam is directly brought to the plant material in SD while the material is initially soaked in water and heated to its boiling point in the case of HD . It appears that the type of distillation influences the selectivity of the process towards terpenes. The recent study of Fiorini et al. compared the chemical composition of essential oil from Felina cultivar obtained by SD and HD. They noticed that with SD a greater content of monoterpenes is obtained compared to sesquiterpenes . On the contrary, HD led to an abundance of sesquiterpenes compared to monoterpenes.
Caryophyllene remains the most abundant sesquiterpene in the EO regardless the process used. Another observation is that cannabinoid content increased significantly when using HD . This can be explained by an increase in the decarboxylation reaction with the HD process, which leads to their alcoholic form that possess a higher volatility. HD is considered as a better process due to the higher percentage of bioactive compounds extracted. This is because, for SD process, a lower pressure is involved, and the steam does not penetrate uniformly the plant material. Therefore, more time is needed to extract components with higher boiling points . Different temperatures were tested during SD and HD of cannabis inflorescences. The optimum temperatures are 110 ◦C and 130 ◦C for HD and SD, respectively. The EO yield increases with temperature in the case of SD, where higher temperatures are needed probably due to slower extraction kinetics . Extraction partition during HD, combined with the effect of grinding, have been explored . Interestingly, monoterpenes are extracted in the earliest minutes, thus a high-monoterpene content EO is recovered in the range of 0–10 min while the sesquiterpene-rich fraction is collected after 80 min. Ground material leads to an additional increase in monoterpene content but lowers the sesquiterpene fraction. It is worth noting that the cannabinoids are extracted in the last minutes, shorten distillation times will provide a cannabinoid-free EO.
The main objective of studies dealing with the extraction of terpenes from cannabis using CSE is the identifification of these compounds. Cannabis EO are well extracted with both polar and nonpolar solvent , however Namdar et al. determined that a mixture of polar and nonpolar solvents results in the most effificient extraction of terpenes and cannabinoids from inflflorescences. Indeed, the authors showed that the solvent mixture hexane:EtOH is the most effificient for the extraction in comparison with pure hexane and ethanol. The use of polar solvent benefifits to the cannabinoids yield . Although the operating conditions are not detailed, L/S ratios vary in the range of 5–50 mL/g, the extractions last up to 1 h and the application of heat does not seem necessary . Besides, high temperature during extended extraction time may cause a loss of volatile compounds and thus lower the EO yield.