Solubility of (+)-catechin in water and water-ethanol mixtures within the temperature range 277.6–331.2 K: Fundamental data to design polyphenol extraction processes

(+)-Catechin is a fundamental polyphenol commonly found in nature. Its aqueous solubility is a key parameter for designing and optimizing extraction processes used to obtain phenolic bioactive compounds from plant material. In this work, the solubility of (+)-catechin in water and water-ethanol mixtures was measured spectrophotometrically using a novel shake-flask method (based on a Carousel 12 Plus™ Reaction Station) within the temperature range 277.6–331.2 K. A HPLC-DAD system was also used to confirm the solubility measurements. The novel method was previously validated by determining the solubility of benzoic acid in water at temperatures ranging from 278.5 to 340.9 K and comparing to literature data. Results showed that the aqueous solubility of (+)-catechin increases with temperature and ethanol concentration, a trend that was well correlated using the so-called Apelblat equation. This behavior was supported by the thermodynamic properties of solution (ΔGsol, ΔHsol, and ΔSsol), whose values indicated that the processes of dissolving (+)-catechin hydrate in water and water–ethanol mixtures were endothermic and entropy-controlled.