(−)-Epicatechin Solubility in Aqueous Mixtures\nof Eutectic Solvents and Their Constituents

(−)-Epicatechin\nis a polyphenol present in diverse natural\nsources. It shows positive human health effects, which makes it interesting\nfor the pharmaceutical and food industries. Conventional solvents\nused for polyphenol extraction are mostly toxic and flammable, leaving\nunwanted impurities in the final product. Thus, solubility of (−)-epicatechin\nat 101.3 kPa and 293.15, 303.15, and 313.15 K was experimentally measured\nin water and binary systems composed of 25 wt % of water + 1,3-propanediol\n(13PD), glycerol (Gly), and two deep eutectic solvents based on choline\nchloride as hydrogen-bond acceptor and the previous polyols as hydrogen-bond\ndonors (DES1 and DES2). Solubility results in water were obtained\nusing spectrophotometric and gravimetric methodologies. Overall, (−)-epicatechin\nsolubility varies widely among the studied solvents but only slightly\nwithin the experimental temperature range. Solvents in ascending order\naccording to (−)-epicatechin solubility are water < Gly\n+ water < 13PD + water < DES2 + water < DES1 + water. The\nsolubility of (−)-epicatechin is significantly enhanced by\nintroducing choline chloride into the investigated hydrogen-bond donors\n(HBDs) at a molar ratio of 1:3, accompanied by 25 wt % water. Perturbed-chain\nstatistical associating fluid theory (PC-SAFT) solubility calculations\nwere in quantitative agreement with experimental data.