Natural Deep Eutectic Solvents for the Extraction of Spilanthol from Acmella oleracea (L.) R.K.Jansen

What if the secret to a greener, safer extraction of a bioactive compound was hiding in a mixture of natural molecules? Scientists just found that a simple blend of choline chloride and propanediol can match the performance of ethanol—without the toxicity.

In the quest for greener chemistry, natural deep eutectic solvents (NADES) are emerging as eco-friendly alternatives to traditional organic solvents. These mixtures of hydrogen bond donors and acceptors are not only biodegradable but also non-toxic, making them ideal for extracting valuable natural products. Yet, until now, no one had tested them on spilanthol, the bioactive compound found in the flower heads of Acmella oleracea, also known as the toothache plant.

Researchers screened 20 choline chloride-based NADES, comparing their efficiency to ethanol. They varied extraction time, water content, and temperature, and quantified spilanthol using HPLC-DAD. The standout performer was choline chloride combined with 1,2-propanediol (1:2 molar ratio, plus 20% water), yielding 244.58 µg/mL—nearly identical to ethanol's 245.93 µg/mL. Another promising combination, choline chloride with methylurea, achieved 208.12 µg/mL.

Further experiments revealed that extraction time had minimal impact, while water additions above 20% decreased yields, and higher temperatures up to 80°C improved them. These findings suggest that NADES could replace toxic solvents in producing medicinal extracts, offering a safer, greener path forward.

Key Points

• 20 NADES tested for spilanthol extraction from A. oleracea
• Best yield: ChCl/1,2-propanediol (1:2, +20% water) at 244.58 µg/mL
• NADES match ethanol efficiency; time has least effect