Novel perspective on botanical extraction – Natural deep eutectic solvents (NaDES) as enhancers of biological activity

During the past decade, a new generation of solvents has emerged with a great potential for many industrial applications. They were first coined as deep eutectic solvents by Abbott et al. [1] in 2003 from the Greek term “eutektos” meaning “easily melted.” These solvents can be defined as a combination of compounds, whose melting point is significantly lower than those of the individual components. While deep eutectic solvents gained more attention, the suspicion began to grow that Nature had long discovered these solvents [2]. These compounds include sugars, amino acids, choline, and some organic acids such as malic, citric, lactic, and succinic acids. With the exception of sugars, which may serve as cell energy, the other compounds are present in such large amounts that it does not make sense to consider them as only intermediates in metabolic pathways. All evidence indicates that these compounds must serve a key basic function in living cells and organisms. Interestingly, primary metabolites appear to be perfect candidates for making these natural deep eutectic solvents (NaDES). By mixing betaine and lactic acid in the proper proportions, this natural eutectigenesis phenomenon causes a considerable drop in the melting point, from 120 °C to – 50 °C, thus allowing its use as an extraction solvent. The use of NaDES leads to a strong synergistic improvement of the recovery yield of bioactive compounds such as rosmarinic acid and oleuropein. An increased level of bioactive compounds is only attained when the three components are added together in the critical composition. These new botanical extracts were further investigated regarding their biological properties through various in vitro assays in the field of melanogenesis, anti-ageing, inflammation and photo-ageing. Our methods enhanced the biological activity of botanical extracts using NaDES technology compared to a standard maceration. Due to the diversity of the newly extracted secondary metabolites from botanicals, novel properties could be highlighted.

Keywords: Natural deep eutectic solvents, green chemistry, eutectigenesis.

References:

[1] Abbott AP, Capper G, Davies DL, Rasheed RK, Tambyrajah V. Novel solvent properties of choline chloride/urea mixtures. Chem Commun 2003; 7: 70 – 71

[2] Choi YH, Van Spronsen J, Dai Y, Verberne M, Hollmann F, Arends IWCE, Witkamp GJ, Verpoorte R. Are natural deep eutectic solvents the missing link in understanding cellular metabolism and physiology? Plant Physiol 2011; 156: 1701 – 1705