4 Considerations for Creating Standardized Cannabis Extracts

Researchers based at the Institute of Plant Sciences, Israel have identified and examined some of the key factors in creating standardized, consistent cannabis extracts. Dosing and labeling are currently big issues in the industry and these results could help improve the quality and quantity of phytochemicals in extracts. Enabling patients to have greater confidence in the medicinal cannabis they need and, making sure that recreational users are receiving the product they want to consume. 

The aim of the study was to assess four parameters that must be controlled and considered to create a standardized product. These factors are the grow light position, extraction solvent, drying process, and analytical separation method. The researchers' findings were published in the Journal of Industrial Crops & Products. 

Standardizing terpenes and cannabinoids in cannabis extracts 

Undoubtedly the most well-known cannabis compounds are tetrahydrocannabinol (THC) and cannabidiol (CBD). But, there is also an increasing awareness of the importance of other cannabis-derived chemicals and, the potential medicinal properties they possess. 

While only present at levels of around a tenth of the cannabinoids, many researchers now agree that terpenes may have a complementary effect to that of the phytocannabinoids. Even though this effect may not yet fully be understood, it has sparked significant interest in whole-plant extracts which, in theory, deliver all the natural benefits of the cannabis plant.  

The ambition of this research was to identify the factors that must be controlled in order to produce standardized cannabis extracts with regular, reproducible terpenoid and cannabinoid compositions. 

The effect of the grow light position 

The study found that light exposure for the lower plant parts was 40% of that reaching the upper levels. Further, the team found that the latitudinal location of a plant segment has a significant impact on its phytocannabinoid content; the higher up the flowering stem, the higher the concentration of terpenes and cannabinoids. It is not surprising that as cannabis grows vertically, the uppermost leaves receive the most light facilitating a greater production of organic compounds in this region of the plant. The researchers suggest that better horticultural practices could mitigate this issue including moving the light source throughout the growing period. Or, pruning the lower levels of the plant to enhance the accumulation of desirable compounds in the remaining flowers.

Selecting an extraction solvent 

Aside from the effects of varying light levels, the study also found that ethanol, a polar solvent commonly used for cannabis extraction, worked best for cannabinoid extraction. However, a mixture of polar and non-polar solvents (an ethanol and n-hexane mixture) was most effective for a comprehensive extract of all active compounds. Regardless of where a sample was taken from on the plant, the total amount of cannabinoids and terpenoids extracted using three different solvents showed a clear preference to the mixed solution of polar and non-polar organic solvents. Thus, the institute’s team advise that to achieve maximum yield and a truly whole plant extract, a combination of polar and non-polar solvents is appropriate. 

It should be noted that n-hexane is regulated heavily in pharmaceutical products by the US Food and Drug Administration due to the serious health hazards it poses when consumed or inhaled. As such, the researchers suggest the less dangerous, more tolerated and somewhat more polar solvent heptane as an alternative. 

Selecting a drying method

Interestingly, both the speedvac and rotary evaporator drying methods tested led to the level of terpenes significantly depleting to almost non-detectable levels. Indeed, the only drying method that left the terpenoid and cannabinoid compositions relatively intact was the use of a very gentle stream of nitrogen. Gas flow and rotary evaporation had a negligible effect on the amount of cannabinoids detected in the samples. However, evaporation by speedvac reduced the amounts of THC and cannabigerol (CBG) by a third. Based on these findings the team recommends designing your extraction step with solvents and their initial volume in mind to help reduce the need for evaporation in the first place. They also suggest that the commonly used overnight speedvac drying approach should be avoided altogether. 

The challenges of HPLC and GC analysis 

When bringing the samples to be accurately analyzed, high-performance liquid chromatography (HPLC) proved to have an advantage over gas chromatography (GC). This was due to the high-polarity solvents used for cannabinoid extraction, which could be directly injected into the HPLC system without any further treatment, reducing any chance of additional human error. 

Another well-documented benefit of HPLC is its ability to reliably identify and quantify cannabinolic acids. This is in contrast to the capabilities of GC analysis, which decarboxylases the acidic forms as they pass through the heated injector port, preventing a quantifiable assessment of the extracted compounds. Derivatization prior to GC analysis is an option but, does involve additional work making HPLC the preferred method in the eyes of the researchers behind this study.   

It’s important to note that the reduction in compound levels moving down the flowering stem was detected independently of the detection method used.

Guaranteeing a fair cannabis extract 

Thanks to this research by the Institute of Plant Sciences team, the considerations to be considered when trying to create a standardized cannabis extract are now clearer. The researchers are keen to highlight that far more research is required in this area. In particular, more work is needed to ascertain the threshold levels of cannabinoid and terpenoids required to create an extract that’s effective for treating specific conditions. Without this information, it is impossible to understand what constitutes a good extract from an efficacy perspective. As our understanding of how different chemotypes can be utilized advances beyond anecdotal evidence, the considerations they’ve highlighted will help enable producers to create a consistent product with the chemical profile they desire.