Ultrasonic Extraction with Deep Eutectic Solvents

Deep eutectic solvents (DES) and natural deep eutectic solvents (NADES) are powerful, tunable and environmentally friendly extraction media for botanicals, foods, nutraceuticals, cosmetics and pharmaceutical ingredients. Hielscher probe-type sonicators intensify DES extraction by accelerating mass transfer, disrupting plant cell structures and improving solvent penetration – even when working with viscous solvent systems such as glycerol-based NADES.

Whether you are screening solvent formulations in the lab, optimizing extraction parameters for a specific phytochemical, or scaling up to continuous inline production, Hielscher ultrasonic extractors provide reproducible amplitude control, robust 24/7 operation and scalable processing from milliliters to industrial flow rates.

Why Extract Producers Choose Hielscher for DES Extraction

• Higher extraction efficiency for polyphenols, flavonoids, cannabinoids, terpenes, anthocyanins and other bioactive compounds
• Faster extraction compared with conventional maceration and stirred-tank solvent extraction
• Compatible with DES, NADES, glycerine, water, ethanol and mixed solvent systems
• Effective processing of high-viscosity solvents using high-amplitude probe sonication
• Batch, recirculation and continuous flow-through setups
• Precise control of amplitude, energy input, temperature and process time
• Easy scale-up from feasibility testing to pilot and full industrial production

Why Sonication Improves DES and NADES Extraction

Ultrasonic probe-type extraction using deep eutectic solvents and natural deep eutectic solvents can offer several advantages for the extraction of bioactive compounds. One of the main advantages is the increased extraction efficiency of phenolic compounds and other phytochemicals from natural sources. Deep eutectic solvents are known for high extraction efficiency, which can be even enhances by ultrasonically-assisted extraction. Due to their non-toxicity they are a great solvent option for pharmaceutical and food products. This makes ultrasonic extraction using deep eutectic solvents a green and sustainable method for the recovery of bioactive compounds. The synergetic use of ultrasonication with deep eutectic solvents has been scientifically proven to result in higher yields of various bioactive compounds. Overall, ultrasonic probe-type extraction using deep eutectic solvents and natural deep eutectic solvents provides a more efficient and environmentally friendly approach to the extraction of bioactive compounds.

Ultrasonic Extraction of Anthocyanins with DES

Anthocyanins are valuable natural pigments and antioxidants found in black carrots, berries, grapes, purple corn and other plant materials. Deep eutectic solvents are well suited for anthocyanin extraction because their hydrogen-bonding network can be adjusted to match the polarity and stability requirements of these color compounds. When combined with probe-type ultrasonication, DES extraction becomes significantly more efficient: ultrasonic cavitation disrupts plant cell structures, improves solvent penetration and accelerates the release of anthocyanins into the extraction medium. A study on black carrot anthocyanins using the sonicator UP400St show that choline chloride-based DES, especially when combined with ultrasound-assisted extraction, can provide a sustainable and effective alternative to conventional acidified ethanol or methanol extraction. (cf. Türker et al., 2021)

Ultrasonic Extraction of Polyphenols with DES

Polyphenols, including flavonoids, phenolic acids and related antioxidant compounds, are important target molecules in botanical, food, nutraceutical and cosmetic extraction. Glycerol-based deep eutectic solvents are particularly attractive for polyphenol recovery because their polarity and hydrogen-bonding capacity support the solubilization of phenolic compounds. Probe-type ultrasound further intensifies the process by increasing mass transfer, reducing extraction time and improving contact between the DES and the plant matrix.
A research study used a glycerol-ammonium acetate DES with ultrasound-assisted extraction under optimized parameters such as temperature, DES concentration and ultrasonic amplitude. The result demonstrated that ultrasonic DES extraction enabled efficient recovery of total phenols, flavonoids and antioxidant activity from chinaberry fruits, demonstrating the potential of ultrasonic extraction using DES as a green extraction method for industrial botanical processing. (cf. Jamshed et al., 2022)

What are Deep Eutectic Solvents (DES)?

Deep eutectic solvents (DESs) are mixtures of at least one hydrogen bond acceptor (HBA) and one hydrogen bond donor (HBD), including carboxylic acids and other renewable compounds. According to Cai et al. (2019), “the strong hydrogen bonding interaction between HBA and HBD is the most important factor for the formation of DESs.” [Cai et al. 2019]
For hydrogen bond donors, compounds such as sugars, amino acids, carboxylic acids (e.g., benzoic acid, citric acid, succinic acid) or amines (e.g., urea, benzamide) are often used. The chemical interaction potential of hydrogen bond donors is the major factors contributing to formation and efficiency of deep eutectic solvents. Halide salts such as choline chloride or zinc chloride can be also used in conjunction with the hydrogen bond donors. Other choline chloride-based deep eutectic solvents are formed with malonic acid, phenol or glycerine. As result of the strong hydrogen-bonding interactions, the melting point of deep eutectic solvents is significantly reduced when compared to its individual components. In contrast to conventional solvents (e.g., ethanol, methanol, hexane, butane etc.) deep eutectic solvents are non-volatile, which means they have a very low vapour pressure and are thereby hardly inflammable. The toxicity of deep eutectic solvents is low, their biodegradability is high, and the necessary precursors are inexpensive, easily and plentiful available as well as renewable.
Natural deep eutectic solvents (NADES) are even more eco-friendly as all precursors are sourced from natural sources. Deep eutectic solvents also offer a tunable solvency based on the chemistry of the solute and the species used to create deep eutectic solvents. Some natural deep eutectic solvents exhibit a high viscosity and they are therefore not very suitable for batch extraction. However, natural deep eutectic solvents with higher viscosities can be successfully applied as solvents in ultrasonic flow-through extraction.

The table below shows a few exemplary compositions of Natural Deep Eutectic Solvents (NADES) for the extraction of phytochemicals:

How Does Ultrasonic Extraction with Deep Eutectic Solvents Work?

Ultrasonic extraction is based on the sonomechanical effects of high-intensity, low-frequency ultrasound. To promote and intensify the extraction of botanical compounds (i.e., bioactive substances) via ultrasonication, high-power ultrasound waves are coupled via an ultrasonic probe (also called ultrasonic horn or sonotrode) into the liquid medium, i.e. the slurry consisting in the botanical raw material and the (natural) deep eutectic solvent. The ultrasound waves travel through the liquid and create alternating low-pressure / high-pressure cycles. During low-pressure cycles, minute vacuum bubbles (so-called cavitation bubbles) are created, which grow over several pressure cycles. During those cycles of bubble growth, the dissolved gases in the liquid enter the vacuum bubble, so that the vacuum bubble transform into growing gas bubbles. After growing over several cycles, the vacuum bubbles reach a certain size at which they cannot absorb more energy, so that they implode violently during a high-pressure cycle. The bubble implosion is characterised by intense cavitational forces, including very high temperature and pressure reaching up to 4000K and 1000atm, respectively; as well as corresponding high temperature and pressure differentials. These ultrasonically generated turbulences and shear forces break plant cells up and release the intracellular bioactive compounds into the (natural) deep eutectic solvent. Ultrasonic extraction opens the cell structure of botanicals and intensifies mass transfer between plant material and solvent. Sonication promotes thereby the efficacy of natural deep eutectic solvents. Ultrasonic extraction with (natural) deep eutectic solvents results in exceptionally high yields within a very short processing time.

Power ultrasound waves disrupt the cell structure of botanicals, release the bioactive compounds and promote the mass transfer between the plant material and the solvent (e.g., deep eutectic solvents).

The combination of ultrasonic extraction with (natural) deep eutectic solvents gives you the opportunity to combine the process intensifying power of ultrasound with the remarkable solubilizing effects and outstanding designability of deep eutectic solvents. Due to the superior efficiency of ultrasonic extraction, ultrasonicators are also successfully used for water extraction.
Contact us now to learn more about the powerful ultrasonic extraction application using deep eutectic solvents!

Ultrasonic Extractors for Lab, Pilot and Industrial DES Extraction

Ultrasonic extraction is a reliable processing technology, which facilitates and accelerates the production of high-quality extracts from various botanical as well as any solvent. Ultrasonic extraction is highly compatible with (natural) deep eutectic solvents, which are favourable due to their excellent solubilizing power, designability to the extract, sustainability, biodegradability, and eco-friendliness. The combination of the process intensification of power ultrasound with the advantages of (natural) deep eutectic solvents gives this process technology superiority on many levels. Hielscher Ultrasonics portfolio covers the full range from compact lab ultrasonicators to industrial extraction systems. All of them are of course suitable for the extraction with deep eutectic solvents.
Our long-time experienced staff will assist you from feasibility tests and process optimisation to the installation of your ultrasonic system on final production level.