In the world of Cannabis’ extracts there are different methods of extraction, each with its own qualities and advantages and disadvantages. But what does science say about the different techniques in use? The answer is in a new review published by Multidisciplinary Digital Publishing Institute (MDPI), editor specialised in scientific journals.
Techniques for extraction of the bioactive compounds of therapeutic Cannabis: the study
The Cannabis’ industry is in fast expansion, therefore, the development of products and innovative ways of extraction have become a crucial aspect in the world of research based on the plant. Published in January 2022, the study titled “A Comprehensive Review on the Techniques for Extraction of Bioactive Compounds from Medicinal Cannabis” was created precisely with the purpose of analysing and comparing the different techniques in use nowadays and with an eye on the next steps to take.
This research points out not only the principle bioactive compounds of Cannabis, but also studies the different techniques to maximise extraction of the phytochemicals substances, discusses the critical factors which influence the end results of extraction, explains how to reduce efficiently the costs of extraction and phytochemical isolation and reviews the available techniques. Also, the final goal for the future is to offer considerations for a safer and more efficient process of extraction that is also sustainable.
To reach this goal, researchers have scrutinised all the papers on the subject available and have created a panoramic view of the different methods of extraction in use today to recover the bioactive compounds of therapeutic Cannabis.
Which are the factors that influence the efficiency of extraction?
For researchers, the factors which influence the efficiency of extraction are diverse, but it’s important to start from the proprieties of the plant itself.
“The plant materials play a major role in the efficiency of extraction of their bioactive compounds. Every plant material has a specific origin, structure and specific phytochemical substances; thus, the extractability of phytochemicals varies based on the type of material. With the same plant material, different parts, like leaves, stalks, roots and flowers, have a different extractability from the target compounds” the researchers explain. “Additionally, the fresh plant materials, the dried or ground ones with particles of small dimensions, need different methods of extraction when the extraction happens under the same conditions. Despite the absence of specific studies which compare the impact of the different conditions of desiccation and dimension of the particles on the bioactive compounds of cannabis, it’s worthwhile considering future studies for a better selection and preparation of the starting materials for the extraction of the bioactive compounds”.
In addition other factors play a key role, such as the solvent in use, its pH and the relation between raw material and solvent. From the study it emerges that, typically, a combination of polar solvents and less polar ones is more efficient in the extraction of phytochemical substances of the plant material, and smaller the volume of the solvents in use, less is the efficiency of extraction which you can obtain because of the saturation. Also, researchers consider acid solvents capable of breaking the cellular walls more rapidly, increasing the efficiency of extraction.
In addition, even temperature and extraction time influence the efficiency of extraction of the phytochemicals of the plant material: a higher temperature with a longer extraction time leads to a more efficient extraction usually. However, the stability of the phytochemicals can lower when exposed to higher temperatures, because of heat-sensitivity.
To these we add pressure and stir to which the compound is submitted: studies have confirmed that the stir increases significantly the efficiency of the phytochemical extraction compared with no stirring as submitting the compound to high pressures; And, it seems that the longer the time of extraction the higher amount of phytochemicals are extracted.
Comparing methods of extraction: conclusions
Based on these considerations, it’s clear how important the different techniques of extraction are and these can be classified in 2 main groups: conventional and advanced; in the conventional methods there’s the extraction with pressurised fluids, the one in subcritical CO2, the extraction in supercritical CO2, the one assisted by electric field pulsed non-thermal, MAE, UAE and the extraction by enzymes.
“In some cases, the advanced techniques of extraction show more efficiency compared with the conventional ones, although, the costs of implementation on industrial scale are a great limit of the advanced techniques” researchers have added and criticise the scarcity of papers on therapeutic Cannabis – a problem we’re not faced with in relation to Cannabis for industrial purpose – and it might be caused by the different laws present in each country.
“Deeper investigations to optimise all the factors listed before might be of advantage to recover the bioactive compounds both from industrial and therapeutic Cannabis. Because the optimisation of these factors can prove really costly, time and work consuming, the use of mathematical models of prediction could accelerate the process of optimisation both for the conventional methods (for example, Soxhlet extraction, maceration, hydrodistillation and steam distillation) and advanced ones. Also, the impact of the variations linked to the season, to geographical location and to the type of Cannabis (strain, chemotype and chemovars) on the recovery of phytochemical substances in the extracts or in the oils of cannabis should be taken into consideration for future studies too”, researchers have concluded.