Supercritical Fluid Extraction’s Effectiveness in Essential Oil Extraction Reviewed

A recent review article by scientists from the Iran University of Science and Technology in Tehran and the Hamadan University of Medical Sciences in Hamadan explored how supercritical fluid extraction (SFE) can help extract essential oils from plants. Their findings were published in the Journal of Chromatography A (1).

Woman pouring eucalyptus essential oil into bowl on wooden table | Image Credit: © Pixel-Shot - stock.adobe.com

Essential oils (EOs) are aromatic and volatile compounds that can be extracted from plant parts, including leaves, seeds, flowers, and fruits. These typically have aromatic compounds and unique smells and are used in aromatherapy. The chemicals in essential oils can also interact with the body in various ways; for example, inhaling the aromas from essential oils can stimulate the limbic system, a part of the brain that can play a role in emotions, behaviors, sense of smell, and long-term memory (2). Further, essential oils are known for antimicrobial, anti-inflammatory, and antioxidant effects, leading to their use in industries such as pharmaceuticals, textiles, and food.

Read More: GC and Spectroscopy Used to Characterize Essential Oil

Supercritical fluid extraction (SFE) is one of the methods used for obtaining EOs from plants, known for being efficient in recovering compounds and having a benign and non-explosive nature. SFE occurs when a supercritical fluid, or a highly compressed fluid combining liquid and gas properties, is used to extract a material (3,4). This typically involves reducing the temperature or pressure of the extraction fluid to recover the extracted material. The technique, which uses supercritical CO₂ as extraction media, is viewed as an environmentally friendly sample treatment method (5).

However, while there are various pieces of existing literature on using supercritical fluids for extracting plant essential oils, there is still much to explore with combining different techniques for enhancing the SFE process. In this review, the scientists presented a sophisticated framework that combines SFE with EO extraction methods. This involves various methods, including the integration of pressurized liquid processes, ultrasound assistance, steam distillation integration, microfluidic techniques, enzyme integration, adsorbent facilitation, supercritical antisolvent treatments, molecular distillation, microwave assistance, milling process and mechanical pressing integration.

This approach, in addition to adding value to the process, also promotes multi-purpose EO utilization. This review advocates for optimizing various operational factors within integrated SFE; this includes pressure, temperature, co-solvent usage, energy input, extraction/separation time, matrix interactions, and sc-CO₂ flow rate. In doing so, the overall effectiveness of these methods could significantly increase. Integrating SFE can provide two advantages: it presents a viable economic solution while paving the way for obtaining EO products on a larger scale, maintaining their purity, and meeting the demands of various industries, such as food, cosmetics, and health care.

The scientists hope their review will foster the exchange of knowledge among sub-disciplines within the realm of integrated SFE for EOs. Their ultimate goal is to collaboratively address challenges associated with intensified SFE; in doing so, this will lead to essential oils being created that are of superior quality and safety. In turn, this will also create new opportunities for widespread and commercially viable applications of these techniques.

References

(1) Dashtian, K.; Kamalabadi, M.; Ghoorchian, A.; Ganjali, M. R.; Rahimi-Nasrabadi, M. Integrated Supercritical Fluid Extraction of Essential Oils. J. Chromatogr. A 2024, 1733, 465240. DOI: 10.1016/j.chroma.2024.465240

(2) West, H. What Are Essential Oils, and Do They Work? https://www.healthline.com/nutrition/what-are-essential-oils#how-they-work (accessed 2024-8-20)

(3) What is a Supercritical Fluid? SciMed Ltd 2024. https://www.scimed.co.uk/education/what-is-a-supercritical-fluid/ (accessed 2024-8-22)

(4) Supercritical Fluid Extraction. Elsevier B.V. 2024. https://www.sciencedirect.com/topics/chemistry/supercritical-fluid-extraction (accessed 2024-8-22)

(5) Supercritical Fluid Extraction. Elsevier B.V. 2024. https://www.sciencedirect.com/topics/nursing-and-health-professions/supercritical-fluid-extraction (accessed 2024-8-21)