Differences in yield appear depending on the state of the material and the particle size. Considering the need to find sustainable processes, it also seems important to explore eco-friendly solvent extraction. UAE is an extraction technique using ultrasound waves, mechanical vibrations that pass through the extraction medium. The waves create acoustic cavitation through the generation of cycles of expansion and compression, inducing the formation of bubbles which expand and collapse. These effects provoke the destruction of cell walls, thereby releasing the cell contents . Table 2 summarizes the different operating conditions used and the results obtained in the different studies using UAE process for the extraction of PC from cannabis. Most UAE is done using an ultrasonic bath with methanol or its aqueous mixture as a solvent. These two solvents are often used for the extraction of antioxidants from plants . The influence of the nature of the solvent on the extraction of PC using ultrasounds has been carried out on defatted seed and meal . The solvents used are water, MeOH, EtOH and acetone at various concentrations. Pure solvents and water led to a lower extraction of PC in comparison with a mixture of aqueous solvents, emphasizing the importance of the polarity of the solvent for the extraction. The optimum yield is obtained for an aqueous mixture of 75% or 80% acetone.
Microwave-assisted extraction , pressurized liquid extraction , extrusion and rapid solid–liquid dynamic extraction have also been used to recover PC from cannabis. Microwaves are electromagnetic radiations that can penetrate plant biomass and interact with polar molecules. The water contained in the biomass absorbs the microwave energy and induces rapid heating of the cells, causing their disruption and the release of the desired components . MAE is an excellent green extraction technology and is particularly appropriate for the recovery of polar molecules such as phenolic compounds from plant materials . The operating conditions tested were water as solvent with liquid/solid ratios between 4 and 6 mL/g, a microwave input power equal to 440, 700 or 1100 W, and times of extraction ranging from 1 to 5 min. The optimum conditions obtained by applying the response surface methodology are a L/S ratio of 6 mL/g, an input power of 700 W, and an extraction time of 5 min. Extraction by ultrasounds of the biomass pretreated by microwaves yielded respective TPC and TFC contents of 13.31 mg GAE/g FW and 0.19 mg LUE/g FW. The resulting extract showed 27.52% of DPPH inhibition and a reducing power of 15.64 µmol Fe/g FW. Similarly to ultrasounds, the authors underlined the influenceof the microwave power, in particular the appearance of degradations due to an excessive temperature in the material generated by microwave power and its interaction with time. Pressurized liquid extraction is a technique used to perform extractions from solid and semi-solid samples under pressure. Accelerated solvent extraction is an equivalent technique, the equipment named identically can operate at room temperature as well as temperatures above the boiling point of solvents, using pressure to keep the solvent in its liquid state . Like MAE, only a few studies have used PLE for the recovery of PC from cannabis. Kitryt˙e et al. used this technology to develop and optimize a multi-step biorefining process for the isolation of cannabinoid and antioxidant fractions from hemp aerial parts.
Their biorefining approach included three consecutive processes, a supercritical CO2 extraction for the isolation of cannabinoids, a PLE for the extraction of PC, and a fifinal step with enzyme assisted extraction to break the cell wall and release its interesting compounds. During the PLE extraction, acetone was applied during optimized conditions of extraction , followed by an EtOH aqueous mixture in the same conditions. The acetone and ethanolic fractions resulted in TPC contents of 5.02 mg GAE/g DW and 23.52 mg GAE/g DW of initial plant material, respectively. In accordance with the cited results, most identifified flflavonoids were in the ethanolic fraction. Temperature was an important parameter: an increase to 100 ◦C enables better extraction of PC while extraction at 130 ◦C leads to a color change and potential degradation of PC. In addition, the ethanolic fraction showed the highest antioxidant capacity. A strong correlation was found between PC and the antioxidant activity of the extract, in particular using ABTS assay. ASE is usually considered to be an interesting technique to replace CSE because a better extraction efficiency is achieved using less solvent in a shorter time as in the work of Bassil . The focused was on the extraction of coumaric and ferulic acids from hemp hurds and dust. ASE yielded 1.5 times more total phenolic content in 30 min than CSE in 24 h. However, ASE was equivalent to CSE in the case of dust.The terpenes are among the main compounds of the essential oil of cannabis . Cannabis’ EO is a liquid with a yellow color more or less pronounced, composed of monoand sesquiterpenes but also of other molecules such as terpene alcohols and cannabinoids.Diverse biological activities have been associated with C. sativa EO including insecticidal, nematicide, antimicrobial, fungicidal, anti-leishmanial, antioxidant, anti-acetylcholinesterase or neuroactive activities . The terpenes present in cannabis EO are responsible for the smell of the plant . Based on the studied articles, the yield of cannabis EO can reach up to 0.55% of dry matter , the most abundant monoterpene found is often β-myrcene. This compound described in Figure 4 have demonstrated antiinflammatory, analgesic, and anxiolytic activities and is used as a flavoring agent, solvent oradditive of lubricating oils.
Caryophyllene, also used as flavoring agent, is the most abundant sesquiterpene in many cultivars. Other sesquiterpenes present in significant quantities such as humulene and caryophyllene oxide can be identified in the EO of cannabis, the latter is the degradation product of caryophyllene.These compounds have shown an important anti-inflammatory activity as well as anticancer, analgesic and antipyretic properties, mainly for caryophyllene and caryophyllene oxide . Since terpenes constitute the major components of cannabis EO, studies of EO are often linked to terpenes. Cannabis EO yield and the terpene contents vary significantly according to the varieties, and between monoecious and dioecious varieties . Moreover, sesquiterpenes are the highest in the earlier harvest time while monoterpenes appear to increase in comparison to sesquiterpenes in the late harvest time, especially when the crop is subject to a water stress .