Impact of Deep Eutectic Solvents and their Constituents on the Aqueous Solubility of Phloroglucinol Dihydrate

Abstract

Phlorotannins are highly bioactive phenolic compounds mainly found in brown algae. Phloroglucinol is the basic unit from which phlorotannins polymerize. Deep eutectic solvents (DES) are potentially beneficial for increasing phenolics solubility, therefore good solvent candidates for phlorotannins extraction processes. Solubility measurements were performed for phloroglucinol in pure water and aqueous mixtures of DES or their constituents, i.e., different hydrogen bond donors (HBD) and choline chloride (ChCl). The stable crystal form of the phenolic in equilibrium was phloroglucinol dihydrate within the studied temperature range (293.15-313.15 K) and water weight fractions (? 0.25). The water + ChCl + HBD mixtures yielded higher solubility for phloroglucinol dihydrate than the corresponding water + HBD or water + ChCl mixtures. Solubility predicted with PC-SAFT was in quantitative agreement with the experimental data. The solubility behavior of phloroglucinol dihydrate in the different mixtures was related to the hydrogen bonds formed using molecular dynamics and PC-SAFT.