Deep eutectic solvents (DESs) are a relatively new type of solvent that have attracted the attention of the scientific community due to their environmentally friendly properties and their versatility in many applications. Many possible DESs have been described and, thus, it is not easy to unequivocally characterize and generalize their properties. This is especially important in the case of the (eco)toxicity information that can be found for these mixtures. In this review, we collect data on the human and environmental toxicity of DESs, with the aim of gathering and exploring the behavioral patterns of DESs. The toxicity data found were analyzed attending to different factors: hydrogen bond donors or acceptors that form part of the eutectic mixture, pH, and the presence of organic acids in the DES molar ratio of the components, or interactions with natural compounds. In the case of ecotoxicity, results generally depend on the biomodel studied, along with other factors that have been also revised. Finally, we also carried out a revision of the biodegradation of DESs.

Several thermophysical properties (density, refractive index, speed of sound, surface tension, dynamic viscosity, static permittivity and vapour pressure) of five compounds classified as green solvents derived from biomass (furfural, furfuryl alcohol, levulinic acid, ethyl levulinate, butyl levulinate) have been obtained from 278.15 K to 338.15 K. A comparative study has been carried out and information regarding molecular interactions and structure has been obtained.

Deep eutectic solvents are liquid mixtures of solid components at room temperature, which present exceptional properties: high solvent capacity, high biodegradation, low volatile organic compound character, and relatively low toxicity. Furthermore, there are an important number of DES described, formed by different components and ratios, and thus, the studied applications are also numerous. In this review, we focused on the applications related to health. One of the most promising applications of DES is the development of oral liquid formulations of poorly soluble active pharmaceutical ingredients, although it currently remains at an early stage. We have analyzed the potential and limitations of DES with this regard. Furthermore, DES have been used as synthesis media. In this work, we revised the use of DES to obtain bioactive natural products via synthesis or extraction process. Finally, the usefulness of DES in other interesting applications for promoting health has been also examined: this is the case of genomics studies, nano-carriers for the encapsulation of anticancer drugs or stabilization of samples for medical purposes.

The toxicities of a series of glycerol mono-, di-, and trialkyl ethers against Vibrio fischeri bacteria have been determined. A systematic study has been carried out and the possible structure–toxicity relationships have been discussed using different QSAR models. Inhibition of bioluminescence after 30 minutes of exposure shows relatively low toxicity of many of the glycerol derived chemicals studied. Results indicate that, as a general rule, the ecotoxicity increases with the length and number of substituents. However, if the size of the molecule increases, an extra substituent at position 2 makes the toxicity lower than that of the corresponding analogues.