NADES solvents – a green revolution

AUTHOR: Ph.D. Manuela Panić, Nades Design

Environmentally acceptable, natural low-temperature eutectic solvents (NAtural Deep Eutectic Solvents) have a low melting point, low volatility, non-flammability, low vapor pressure, chemical and thermal stability, their price is low and they are easy to prepare on an industrial scale. Therefore, they are good candidates for carrying out plant extraction in industry.

Nowadays, plant extracts have drawn attention for their positive effects on human health. Plant extracts are rich in various biologically active compounds such as antioxidants, essential oils, aromas, vitamins, colors and pigments, organic acids, pectins and others, which possess antioxidant, antibacterial, antiviral, anti-inflammatory, antitumor and/ or antimutagenic and other positive activities1. Therefore, plant extracts have found wide use in the pharmaceutical industry, in the food and beverage industry, and in the cosmetic industry.

Consequently, the extraction and identification of biologically active compounds from different plants have become a very important area of scientific research. The market value of plant extracts in 2022 is estimated at 34.4 billion USD, and the market is still growing. The current technology on the market of plant extracts is not in accordance with innovations and ecological trends, and it is necessary to find a solvent that would dissolve both hydrophilic and lipo­ philic phytochemicals from plants, because biologically active compounds from plants are a chemically diverse group of compounds. Some of them are soluble in water as a solvent, while most dissolve in petroleum­based solvents. Petroleum­based solvents used in extract preparation are toxic, flammable, volatile and explosive, resulting in air pollution. These solvents cause 60% of all industrial emissions and 30% of emissions of volatile organic compounds. Although is the fact that in the 21st century according to the directive 2009/32/EC (Food) it is still allowed to consume 2.9 mg/kg of hexane or 6 mg/kg of dichloromethane per day, the goal of the green deal is to replace such solvents with ecological acceptable alternatives.

Natural deep eutectic solvents (NADES), which can extract both polar and non­polar biologically active compounds, showed great potential for application in extraction of biologicaly active compounds. NADES are mixtures obtained by the complexation between a hydrogen acceptor such as non­toxic qua­ ternary ammonium salt (e.g. cholinium chloride) and a naturally­derived uncharged hydrogen­bond donor (e.g. amines, sugars, alcohols and carboxylic acids) in a certain molar ratio, bonded with hydrogen bonds between NADES components2,3 (Figure 1).

Structurally, NADES consists of at least two inexpensive, non­toxic and easily available components which are able to self­associate at a certain molar ratio to form a new eutectic phase characterized by a melting point below 100°C. Beside their green character, one of the prominent characteristics of these solvents is the possibility of designing their structure, and thus changing their physical and chemical properties, which consequently affects the possibility and effectiveness of their application in the selective isolation of biologically active molecules. Since the number of possible chemical structures of these solvents is tremendeous, as many as 106 different solvents, there is the possibility of designing them for specific purposes4 .

NADES fully represent the green chemistry principles owning to their specific properties: (i) the cost of NADES is comparable or even lower than conventional solvent; (ii) sustainable production with 100% atom economy production, (iii) chemical and thermal stability, (iv) non-volatility and non-flammability, (v) low toxicity and biodegradability. Since NADES building components can be considered safe for human consumption NADES extracts could be used as ready­to­use in food and pharmaceutical industry without demanding and expensive downstream purification steps5,6.

Another positive aspect of the use of these solvents in extraction processes is related to the efficiency of NADES extraction compared to conventional solvents. The true benefit of each plant is delivering at least 100 times higher concentrations of biologically active molecules compared with conventional solvents used now in the industry. Comparing the activity of NADES­based extracts with the extracts on the market, NADES extracts possess superior activity. Furthermore, NADES solvents also affect the stability of biologically active compounds. Therefore, by applying the extracts prepared in this way, the added value of the final product is achieved, which can have an improved composition and better, longer stability. NADES extracts are characterized by antioxidant properties, increase product longevity and bioavailability7,8. Such extracts have shown good compatibility with skin cells, and their biological effectiveness such as hydration, anti-aging and UV protection has been proven9

A team of scientists from the Faculty of Food and Biotechnology decided to enter the market with NADES solvents and products based on them. Female scientists are trying to bridge the gap between academia and industry and bring sustainable green products to market. Their story with NADES solvents began in 2013 in the academic community, and since then they have been working and creating innovations in the field of green chemistry. They believe that now is the right time and that the industry is ready to implement green solvents in their products.

As entrepreneurs, they started a journey in SPOCK start up incubator. They received the first grant from the ACT group to start their business and develop the products. They are also the winners of Green Hackaton competition in 2022, which was organised in cooperation with the British Embassy and Algebra LAB at the Greencajt festival. They received support from EIT Food through the EWA program implemented by Lean Start Up Croatia, where they won first prize. Recently, they won 3rd place at the LAQOTHON competition for the best green idea.

References:

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2 M. Ruesgas­Ramon, M. C. Figueroa­Espinoza and E. Durand, J. Agric. Food Chem., 2017, 65, 3591–3601.

3 M. A. R. Martins, S. P. Pinho and J. A. P. Coutinho, J. Solution Chem., 2019, 48, 962–982.

4 A. Paiva, A. A. Matias and A. R. C. Duarte, Curr. Opin. Green Sustain. Chem., 2018, 11, 81–85.

5 K. Radošević, N. Ćurko, V. Gaurina Srček, M. Cvjetko Bubalo, M. Tomašević, K. Kovačević Ganić and I. Radojčić Redovniković, LWTFood Sci. Technol., 2016, 73, 45–51.

6 E. Wang, Y. Yin, C. Xu and J. Liu, J. Chromatogr. A, 2014, 1327, 39–48.

7 J. M. Silva, E. Silva, R. L. Reis and A. R. C. Duarte, Sustain. Chem. Pharm., 2019, 14, 100192.

8 Y. Dai, E. Rozema, R. Verpoorte and Y. H. Choi, J. Chromatogr. A, 2016, 1434, 50–56.

9 P. Manuela, S. Drakula, G. Cravotto, R. Verpoorte and M. Hruškar, Innov. Food Sci. Emerg. Technol., 2020, 66, 102514.

For more information about the products and the NADES team, visit their website www.nades­design.hr or social media : www.linkedin.com/in/nades-design-a2aab0221/ www.twitter.com/NADES_Design?s=20&t=t6cJ8_Gp9_xW0GQ­Q3WHsA)