Ionic liquid-supported solid-liquid extraction of bioactive alkaloids. II. Kinetics, modeling and mechanism of glaucine extraction from Glaucium flavum Cr. (Papaveraceae)

The temperature dependence on the global kinetics of both methanol and 1-butyl-3-methylimidazolium acesulfamate ([C(4)mim][Ace])-supported extraction of the bioactive alkaloid S-(+)-glaucine from plant material of Glaucium flavum Crantz (Papaveraceae) was measured and a comparative analysis in respect to the extractant type was performed. The experimental data was fitted with high coefficients of determination by means of an empirical model showing that the extraction process in both cases follows second-order kinetics. The concentration at saturation, C-s, extraction rate constants, k(2), initial rates of extraction, h, and activation energies of extraction, E-a, were then calculated and discussed. The obtained results give a considerable advantage to the Ionic liquid-supported (IL-supported) extraction procedure due to the faster and quantitative glaucine transfer, regardless the temperature. A plausible extraction mechanism scenario, describing the whole system in terms of solute-solvent, solute-matrix and matrix-solvent interactions at every stage of the extraction process was proposed. As a result, the apparent kinetics and yield of the IL-supported extraction were attributed to the cell wall modification by H-bonding interactions between both ions of [C(4)mim][Ace] and cellulose, resulting in the plant tissues disruption. The latter was further unequivocally confirmed by means of scanning electron microscopy. The kinetics parameters obtained were then implemented into a model for the prediction of glaucine amount extracted in 1 M [C(4)mim][Ace] water solution at any temperature and time with good predictive ability. (C) 2012 Elsevier B.V. All rights reserved.