Solubilities of Anthraquinones in Pressurized Solvents

Abstract

Anthraquinones (AQs) are an important category of secondary metabolites present in various vegetable species [1]. They are highly bioactive compounds, potentially useful for therapeutic applications, as antiviral, anti-bacterial and anti-cancer agents [2-5]. Extraction processes using pressurized hot water and supercritical fluids offer an environmentally friendly alternative to traditional extracting and purifying methods applied to anthraquinone-containing plants [6,7] . Knowledge on high-pressure phase equilibria of AQs + solvent mixtures is required to evaluate the potentiality of these processes. The need is for both, experimental data and thermodynamic models that are able to predict phase boundaries at different process conditions. In this work, the solubility of 1,4-dihydroxy-9,10-anthraquinone (quinizarin) in pressurized hot water have been measured, using a simple and reliable dynamic method. For the binary quinizarin + H2O, the measurements covered a range of 333-463 K and pressures closed to 3, 6 and 9 MPa. The group-contribution with association equation of state GCA-EOS [8] was used to calculate solid-liquid equilibria of binary mixtures of AQs with pressurized hot water.