Type V deep eutectic solvents: Design and applications

Liquefying Flavonoids with Terpenoids through Deep Eutectic Solvent Formation

“…Abranches et al [11] already discussed how the resonance structures of thymol render the hydrogen of its hydroxyl group a better HBD site and the oxygen a worse HBA site, while menthol has a regular hydroxyl group. Lone HBAs, such as flavone and flavanone, have also been proposed as powerful DES-forming compounds [15]. Thymol mixed with flavone or flavanone fits that criterion resulting in negative deviations from ideality.…”

“…However, strongly interacting DES can also be obtained using non-ionic compounds such as HBA and HBD, which are classified as type V [11,15].…”

“…More fundamental studies are needed to understand the molecular interactions in the liquid phase, between solvents and solutes, and provide a more efficient design of the best DES for a given application. Some success on the a priori design of DES has been achieved using the Conductor-like Screening Model for Real Solvents (COSMO-RS) [15,[20][21][22]. This statistical thermodynamics-based model uses a quantum chemistry description of molecules (σ-profiles, calculated from σ-surfaces) to predict their chemical potential (and derived properties, namely activity coefficients and excess properties) in liquid mixtures [23][24][25].…”

“…Previous works suggested that type V DES should be formulated using HBA, such as alcohols, ketones or amines, and phenolic compounds acting as HBD [11,15]. Given that flavonoid molecules are rich in HBA sites, phenolic-based HBD could be applied to extract flavonoids from natural matrices through "in situ" DES formation by creating specific interactions with the HBD and/or HBA groups of the solutes.…”

“…Given that flavonoid molecules are rich in HBA sites, phenolic-based HBD could be applied to extract flavonoids from natural matrices through "in situ" DES formation by creating specific interactions with the HBD and/or HBA groups of the solutes. These interactions are particularly strong when the HBA cannot form hydrogen bonds with itself (which may be referred to as lone HBA [15]), as observed in betaine-based [10,26], trioctylphosphine oxide-based (TOPO-based) [20,27,28], and diazabicyclo-based systems [29].…”