Researchers and technological developers have spent the better part of a decade creating cutting-edge extraction technologies. Often, many extraction methodologies remained limited to solvents like butane.
The dominance of these solvents would not last forever, however, as “greener” extraction methods came to the fore. A prime example of this is supercritical carbon dioxide (CO2) extraction which is viewed as providing cleaner and safer extractions compared to more traditional solvents like hydrocarbons for extracting non-polar molecules from plants.
A recent study published in the Journal of Food and Chemical Toxicology has demonstrated another exciting methodology for extraction – subcritical water extraction (SWE) – which offers extractors a low-cost and environmentally friendly solvent and methodology devoid of health risks to users. Interest in green solvents that supplant toxic organic solvents that require remediation efforts is growing, and sub- and supercritical fluids have often been chosen for this reason.
The aforementioned study found that SWE of ashwagandha (Withania somnifera), a naturally occurring medicinal plant found in India, was effective at extracting high concentrations of withanoside, withanolide, and steroidal lactone compounds, which purportedly have medicinal benefits for a host of conditions. Ashwagandha is a well-known herb used in Indian Ayurvedic medicine, also known as Indian Ginseng or poison gooseberry. [1,2]
The plants repertoire of medical properties includes preventing gastric ulcers, anti-tumor effects, and cognitive improvements where memory has been damaged, such as in neurodegenerative diseases like Parkinson’s, Huntington’s, and Alzheimer’s diseases.  It’s also demonstrated anxiolytic (anti-anxiety) properties. 
The compounds in ashwagandha, especially withanosides, have traditionally been extracted with organic solvents including hexane, chloroform, ethanol, and methanol. While the best extraction yield (65.6%) was demonstrated using 200°C and 30 minutes, ideal conditions for maximizing the phytochemicals’ antioxidant properties turned out to be 160°C for 20 min.
“SWE at 160°C for 20 min could be used as new method for extraction of bioactive compounds,” the study claims. Pressure was maintained at 10 MPa. It was also added that SWE outperformed (yield, phenolic content, and antioxidant activity) other methodologies tested, namely maceration, Soxhlet extraction, and microwave-assisted extraction. Furthermore, SWE offers tangible environmental benefits. 
- Nile SH, et al. Subcritical water extraction of withanosides and withanolides from ashwagandha (Withania somnifera L) and their biological activities. Food and Chemical Toxicology. 2019;132(110659). [Impact Factor: 4.679; Times Cited: 4 (Semantic Scholar)]
- Singh N, Bhalla M, de Jager P, Gilca M. An overview on ashwagandha: a Rasayana (rejuvenator) of Ayurveda. Afr J Tradit Complement Altern Med. 2011;8(5 Suppl):208-213. [Impact Factor: ; Times Cited: (Semantic Scholar)]
- Chandrasekhar K, Kapoor J, Anishetty S. A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of ashwagandha root in reducing stress and anxiety in adults. Indian J Psychol Med. 2012;34(3):255-262. [Impact Factor: ; Times Cited: (Semantic Scholar)]
Photo courtesy of formulatehealth is licensed under CC BY 2.0.