Hemp, known the world over as a multipurpose crop, has had a significant amount of time in the spotlight recently, this is due to its constituent, cannabidiol (CBD). CBD is a highly beneficial compound with uses dating back centuries and currently is a key player in the pharmaceutical industry. But what is the best way to extract it?
Cannabis sativa, commonly known worldwide as hemp, is considered one of the most widely used and the most ancient of cultivated plants. In the 16th century, this diverse plant was imported from Asia into the European Union countries (1). This herbaceous, wind-pollinated, plant can be found now-days across Europe, Canada, USA and Africa.
This hardy plant is touted across the world as having a significant influence on the economy, being sustainable, with a low impact on the environment, as well as being a significant resource for a number of industries. Hemp is well known in having a range of uses, including, agricultural, phytoremediation, as a food source, cosmetics, building materials and in the pharmaceutical industry (2).
With growing recognition of their nutritional, medicinal and sustainable features, the need to be able to appropriately and adequately remove the beneficial bioactive compounds, such as cannabidiol (CBD), from hemp is ever increasing. With this in mind, there are two questions, what is CBD? And, what is an appropriate extraction method to isolate CBD?
Hemp and CBD
Over recent years, the chemistry and pharmacology of CBD have been the focus of a large number of investigations. CBD is well known as being the highly beneficial, non-psychoactive constituent in Hemp (3). Thankfully, CBD is distributed throughout the Hemp plant, with the highest quantities in the flower and leaves.
CBD is one of the “top-dogs” in the natural medicine world. A huge number of scientific investigations have shown that CBD is able to help a number of conditions, including, as an anti-anxiety, helping the immune system, as an anti-nausea, an antioxidant and as an anti-inflammatory (4). It is able to do this by binding to human cannabinoid receptors, CB1 and CB2. When CBD binds to these receptors, it causes a cascade of processes, leading to the well-known beneficial effects throughout the body (5).
CBD is biosynthesised naturally in the plant, but, in relatively small quantities. In order to achieve high enough quantities desired in the medicinal and pharmaceutical industries, plant material from Hemp must be extracted and processed correctly to speed up the formation of CBD from its precursor cannabidiolic acid (6). The end result of the extraction and distillation process is an essential oil extract, containing, of course, CBD oil.
In general, CBD is able to be extracted from the plant using a large range of different organic solvents, alcohols, heat, Soxhlet extractor, microwaves and distilled through hydrodistillation and steam distillation. However, a number of these methods can have negative impacts on the extract itself and on the environment. Nonetheless, there is a new player waiting in the wings; this is Supercritical Fluid Extraction using carbon dioxide (CO2) (7).
Supercritical CO2 extraction
Supercritical CO2 extraction is a valuable emerging technology that has been used more traditionally in seeds, fruits and vegetable processing and preservation (8). Supercritical CO2 extraction is considered a green-technology, especially considering it is a much more environmentally friendly alternative to the conventional industrial processes (9).
The technique itself is referred to as Supercritical Fluid Extraction technique and has a large number of advantages over the more traditional methods, and this is especially so in preserving thermally sensitive compounds, such as CBD (10). In addition, Supercritical Fluid Extraction minimises the environmental impact, decreases toxic residues, is able to use/re-use by-products more easily and is able to produce high-quality products with high nutritional and pharmaceutical value (11).
Now, you may be wondering what supercritical CO2 is? Supercritical CO2 has characteristics of both CO2 gas and CO2 liquid. This is achieved by holding CO2 at its critical temperature whereby the CO2 no longer is gas or liquid but has properties of both (12). It is becoming more and more popular as an industrial solvent in chemical extraction due to its ability to preserve valuable compounds as well as having low toxicity (13).
A number of studies have used Supercritical CO2 extraction to look at its impacts on the yield of the oil and the number of important constituents in Hemp. They have found that the yield of oil was either similar or higher when it was extracted with supercritical CO2 compared to more traditional methods (14, 15, 16). In addition, Hemp oil extracted using supercritical CO2 had higher levels of important constituents than compared to traditional methods, such as using a Soxhlet extractor (17).
These investigations all confirm that it is an important separation technique in the nutraceutical and pharmaceutical realms and is a good alternative solvent for the extraction of Hemp oil compared to more traditional techniques including microwave, oven-heat and the Soxhlet extractor (18).
The Bottom Line
Hemp, known the world over as an important resource for many industries, especially the pharmaceutical and nutraceutical industries, has one major constituent we are all familiar with, cannabidiol. How you extract cannabidiol from Hemp has left many researchers scratching their heads, but there is an emerging extraction technique that trumps nearly all of them all, CO2 extraction. Using Supercritical CO2 cannabidiol is able to be extracted from Hemp easily and more environmentally friendly than other traditional methods.