Menthol-Based Deep Eutectic Solvent Shows Promise for Greener Phytocannabinoid Analysis
Researchers have identified a menthol-based solvent that could reduce reliance on hazardous chlorinated solvents when laboratories analyze cannabis plant material.
The 2018 study, published in the Journal of Cleaner Production, evaluated a group of hydrophobic deep eutectic solvents (DESs) for extracting four major phytocannabinoids: tetrahydrocannabinolic acid (THCA), cannabidiolic acid (CBDA), tetrahydrocannabinol (THC), and cannabidiol (CBD). The original research paper compared the new solvents with methanol, ethanol, and a conventional 9:1 methanol–chloroform mixture.
Reliable extraction is important for cannabis testing. Laboratories analyze plant material to measure cannabinoid concentrations, compare cultivars, identify contaminants, and examine seized samples. Because processing conditions can convert the acidic cannabinoids THCA and CBDA into THC and CBD, analytical methods must also preserve or accurately account for these related compounds. A review of phytocannabinoid-profiling methods describes how heating and other preparation steps can alter these measurements.
Chloroform has long been used in some extraction procedures, but it presents occupational and environmental concerns. The U.S. Agency for Toxic Substances and Disease Registry notes that chloroform exposure can affect the liver and kidneys and that the chemical can move from contaminated soil or water into the air. These concerns have encouraged researchers to investigate safer alternatives, including alcohol-based solvents and DESs.
Deep eutectic solvents are produced by combining two or more substances whose interactions lower the mixture’s melting point. In this study, the researchers paired menthol with different natural carboxylic acids, creating hydrophobic mixtures capable of dissolving relatively nonpolar compounds such as phytocannabinoids. They also tested whether menthol could be replaced with other common terpenes, including terpineol, linalool, geraniol, and borneol.
The strongest results came from a 1:1 molar mixture of menthol and acetic acid. In the researchers’ comparison, this formulation produced extraction values equivalent to 118.6%–132.6% of those obtained with the methanol–chloroform reference mixture, depending on the cannabinoid measured. It also performed better than methanol and ethanol under the study’s conditions.
These percentages represent relative analytical extraction performance, not the amount of cannabinoid present in a cannabis plant or a measure of therapeutic potency. The experiments were conducted on plant material and used capillary electrophoresis with diode-array detection, so the findings demonstrate laboratory potential rather than a validated replacement for every cannabis-testing or manufacturing process.
The researchers characterized the menthol–acetic acid system as efficient, biodegradable, and less hazardous than conventional organic-solvent approaches. Its ingredients are also relatively accessible, and the solvent can be prepared without a complex synthesis. Those features could make it attractive for routine analytical workflows if further studies confirm its performance across different cannabis varieties, sample types, and operating conditions.
Still, “green” does not automatically mean risk-free. The environmental and biological safety of individual DES formulations depends on their ingredients, concentrations, persistence, and eventual disposal. More recent research has specifically begun evaluating the phytotoxicity of menthol-based hydrophobic DESs, underscoring the need for broader safety testing before widespread adoption.
The 2018 findings therefore represent an early proof of concept: a menthol-based deep eutectic solvent can extract major phytocannabinoids efficiently while potentially reducing the use of volatile, chlorinated solvents. Further work will be needed to assess solvent recovery, long-term stability, matrix effects, scalability, and performance in accredited cannabis-testing laboratories.
