Insights into the Vastly Different Effects of Eutectic Solvents on the Stability of Phenolic Compounds

Eutectic solvents (ESs) have shown stabilizing effects on several molecules. Due to the potential applicability of bioactive compounds, understanding how ESs stabilize them is of great interest in pharmaceutical and related fields. Here, among various ESs, CTU, which comprise thiourea and choline chloride (ChCl), exerted remarkably high stabilizing effects on various phenolic compounds, whereas CU consisting of urea and ChCl exhibited the opposite effects. Using a potent polyphenol, (−)-epigallocatechin gallate (EGCG), as a model compound, we conducted experimental and in silico studies to unravel the underlying mechanisms of the two very similar ESs for the contrasting effects. The results suggest that ESs can affect with great diversity the stability of EGCG by complicated interactions arising from the unique properties of both ESs and their components.