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Terpenes are the building blocks of the smells and tastes we find throughout nature, and we have found a way to extract these organic compounds. Terpene extraction has opened up countless terpene uses from cosmetics to food additives, but how is it done? There’s a number of ways that terpenes are extracted and they vary depending on the desired terpene’s polarity, volatility, and size. All these factors are considered before extraction and processes continue to be refined for each individual terpene.
Hydrodistillation (Steam Distillation)
Hydrodistillation, or steam distillation, is often used to extract aromatic compounds because of their volatile nature (it is worth noting that this method does not work as well for heavier terpenes). Hydrodistillation uses steam and passes it through the plant containing the desired terpenes. The pressure of the steam can be adjusted depending on the sensitivity of the terpenes. After the steam passes through the plant (taking the terpenes with it), the steam is then condensed, creating a water and terpene distillation mixture. The terpenes and the water are then separated leaving just the terpene distillate.
In a study done by the University of Kentucky, Lexington, Department of Pharmaceutical Sciences, they explored how to extract terpenes already released into the atmosphere by plants. To do this, they took a live plant and placed it into a gas chamber. They then had a flow of air entering the chamber and a vacuum line pulling gasses from the chamber. The outgoing gasses were passed through a tenax resin packed pipette to trap the terpenes. The pipettes were changed every 1-4 hours and the terpenes were then pulled from the resin.
Solid-phase Microextraction (SPME)
Solid-phase microextraction is one method of terpene extraction that does not require any solvents. A liquid or gas containing the terpenes is placed into a chamber and then a fiber coated extracting phase is introduced. The fiber pulls the terpenes from the liquid/gas–in some cases the liquid requires agitation. The fiber with the collected terpenes is then placed in a gas chromatography chamber, or other separating instrument, which pulls the terpenes from the fiber and collects them.
The partitioning method is an extraction process that uses two immiscible liquids (liquids that do not mix) to reach an equilibrium. For example, using a methanol extract of cells and cell culture medium with chloroform, researchers at the University of Kentucky, Lexington were able to seperate the terpenes from the solvents. The solvents were then dissolved, leaving behind only the terpenes, which could be seen when they were sprayed with a reagent and heated.
The final method we will discuss is solvent extraction. Solvent extraction has a fitting name because it is done by submerging plant material in a solvent. Typically the solvents methanol, hexane, or ethanol are used. As the plant material sits in the solvent, its terpenes are extracted. After soaking for some time (typically half a day to two days) the plant material is removed and the solvent is evaporated, leaving behind the isolated terpenes.
Luckily, when it comes to terpene extraction there’s a wide array of options to fit the needs of each individual terpene. While one method is best for Gamma-Terpinene, it may not work as well for Para-Cymene. Each terpene is unique and requires unique considerations to achieve the best isolate possible.